Orgo Lab Rutgers Spring 2021

Q9 AM 1. a) In column chromatography (microscale), after loading it with solvent and adsorbent and prior to loading the sample, what is the consequence of letting the sample to run dry? b) When a fraction eluted from a column containing desired substances is analyzed by TLC, the following is the observation seen on developed and visualized (with all methods necessary) TLC plate, what step should be next? 2. Which reason from the dropdown menu would best describe why the 𝛽β -diastereomer of the cholesterol epoxide (side product) can form in the epoxidation of cholesterol experiment? What may be the specific problem one might observe in the TLC process when the reaction mixture is spotted if a student used half the amount of methylene chloride to act as a reaction solvent in the epoxidation reaction you carried out? Why? 3. When spotting the TLC plate in the epoxidation experiment, you place the spots too close to one another on the spotting line. What does this result in? PICK THE MOST ACCURATE ANSWER. 4. Consider the biological reaction below: (Oxalo --> Malate) a) Which of the 2 reactants is the species that is oxidized in the reaction above? b) Which reactant in the synthesis of meso-hydrobenzoin you carry out that is affected in the same manner (is oxidized) as the species in the question above. 5. In the recrystallization process of the meso-hydrobenzoin: a) Which of the following would impact purity specifically in the crystallization stage? b) Which of the following would reduce % recovery of the crystals AFTER the crystals are formed in the crystallization stage? 6. a) What would happen if you used ethanol as the solvent for a reduction involving LiAlH4 (lithium aluminum hydride)? b) You take a melting point of the meso-hydrobenzoin product. Which of the following situations would cause the widening of the range but not the lowering of the upper melting range? Q8 AM 1. DNA has a higher pKa than RNA. When a mixture of the ionic forms of RNA and DNA is acidified at pH 5, only one of the ionic forms is converted to the nonionic form. Which between the ionic forms of DNA and RNA would become nonionic at pH 5? Where (organic or aqueous layer) would this nonionic form be found? 2. You react 1-bromobutane and 2-chlorobutane with sodium iodide in acetone. a) The haloalkane that reacts FASTER is: b) The haloalkane that reacts FASTER has a leaving group that is a: 3. Match the technique mistake or part failure in the Esterification experiment that you were to carry out with the correct undesirable result. -Condensor not cooled with wet paper towel -Apparatus set up straight and not tilting -Not using boiling chips in reaction mixture 4. Which, from below, is/are possible way(s) to increase the yield of a general esterification reaction? (1) Use excess alcohol in the reaction (2) Use excess carboxylic acid in the reaction (3) Use excess acid catalyst in the reaction (4) Using molecular sieves in the reaction mixture to remove water as its formed in the reaction (5) Using calcium chloride pellets in the reaction mixture to remove water as its formed in the reaction 5. The melting point of dibenzalacetone is 110-112ºC. If you find that your sample melts at 112-114ºC, it is likely that:

Q9 AM 1. a) poor separation b) increase polarity of the eluent for the column gradually 2. The planarity of the double bond in cholesterol to allow for attack from either side Streaking of spots, too concentrated 3. Spots bleed into each other 4. a) NADH b) Sodium Borohydride 5. a) Not wrapping test tube with paper towel b) Only letting crystals reamin on Hirsch funnel for a few seconds 6. a) There would be a violent reaction and hydrogen gas would be formed b) Melting point determination made too fast Q8 AM 1. DNA, organic 2. a) less hindered which makes backside attack easier b) weaker base which makes it easier to leave in the rate-determining step 3. -No reflux -Condensate does not collect in sidearm - Product in sidearm contaminated by bumping on reaction flask 4. 1, 2, 4 5. The thermometer in the melting point apparatus is not calibrated

Post Lab 09 - Epoxidation 1. 2. 3. 4. 5. 6.

1. 2. 3. 4. 5.

Solid Mixture: first drop liquid 80°. Completely melted: 92°. Eutectic pt: 65°. REAL melting range?

65-92˚C (Real melting range is from eutetic point to when sample is completely melted)

From figure 5.4 on pg. 91, you distill a liquid mixture of 25% ethanol: 75% water. What would the temperature when the distillate begins to condense in the sidearm (the distillate's boiling point) be? (Select the best representative answer).

80˚C

Look at Fig. 5.3 on pg 90: If you boiled the liquid mixture of 40%cyclohexane and 60% toluene, condensed the vapor mixture it generated and then redistilled that condensed mixture, what would the vapor composition of the mixture resulting from the 2nd distillation be?

93% cyclohexane: 7% toluene

What can one do to obtain a second crop of crystals after initial crystals have been collected? What is the drawback of this method?

The filtrate and washings can be combined and evaporated to the point of saturation to obtain a second crop of crystals. This ups your overall yield but the crystals obtained in this method will not be as pure.

Sources of Error - TLC

The sources of error that could occur in this week's experiment include: Spotting samples too close to one another having the solvent above the spotting line Using a pen instead of a pencil to mark The TLC plate being incorrectly and leading on the filter paper Cross-contamination from other samples No cap on the developing chamber

Post Lab 10 - Reduction 1. 2. 3. 4. 5. 6. 7.

1. 2. 3. 4. 5. 6. 7.

PQ 10 - Reduction 1. Which of the following transformations is/are reductions? 2. In the oxaloacetate in mitochondria to malate transformation, what was oxidized and what was the oxidizing agent? 3. In the malate to oxaloacetate in cytosol transformation, what was reduced and what was the reducing agent? 4. Which of the following solvents WOULD NOT react violently with LiAlH4? 5. The formation of which species would be minimized by the use of excess NaBH4?

1. 3 & 4 (OH --> H , double bond to single bond ) 2. Oxidized: NADH, Oxidizing Agent: Oxaloacetate 3. Reduced: NAD+, Reducing Agent: malate 4. Ether 5. S-Benzoin

The only time the melting point of a sample would be observed higher than expected is:

Calibration of Thermometer (this is the only time that a sample's MP could skew higher)

You have a 1:1 mixture of 2,2,4-trimethylpentane (boiling point: 99˚C) and methoxybenzene (boiling point: 154˚C) that you wish to separate. a) What common criteria would this mixture have to satisfy in order to be separated by either simple or fractional distillation? b) What kind of distillation (between simple and fractional) would be efficient for this mixture? c) Why would the distillation type chosen in question b) be ideal for this mixture?

a) homogenous b) fractional c) boiling point difference and composition

What character of the actual elements (aluminum, silicon, oxygen) present in alumina and silica cause the stationary phase to be very polar?

The electropositive character of the aluminum or silicon and the electronegativity of oxygen creates a very polar stationary phase.

What is the vapor pressure of a sugar solution dependent on?

The vapor pressure of a sugar solution is dependent on the number of water molecules present in a given volume.

When comparing 2 hydrocarbons, why would the larger, higher molecular weight molecule have a higher melting point?

You can expect the larger and higher molecular weight molecule to have a high melting point because there are more forces and therefore more energy is needed to be put in the system to separate.

You carry out a reaction that can potentially form 3 known compounds A, B and C. Compound A that has a melting point of 90°C-92°C, Compound B that has a melting point of 115°C-117°C and Compound C that has a melting point of 132°C-133°C. Only one compound is formed in the reaction and it has been purified. What is the reason you take the melting point of this compound?

To characterize a known compound

You wish to recrystallize a solid that has a melting point of 80-82ºC. Which of the following solvents (assuming all of them have ideal characteristics as solvents for recrystallizing this solid) has a potential causing the solid to oil out during the recrystallization process?

Water (Boiling Pt: 100˚C) because BP is higher than MP of the solid

Safety Quiz 1) What should you always wear over your eyes while in the lab even if your wear glasses? 2) Are contact lenses ever permitted in the Chemistry laboratory in Rutgers? 3) What should you always do before lighting a match in the lab? 4) What heat source should you use to heat flammable organic solvents? 5)How should you dispose of excess organic solvents? 6) What should you try first if a very small fire starts on your desk?

1) Authorized eye protection in one of three types of eyewear: Lab Safety Goggles, Safety Glasses, or Visor Goggles. 2) Not in Rutgers Chem Labs 3) Before lighting a match in the lab, you must pay close attention to flammable liquids/vapors in the area. You must also remember that vapors of flammable liquids are always heavier than air and thus will travel along the top of benches, down drain troughs, and remain in sinks. 4) Flammable organic solvents should be heated using an electrically heated sand bath. 5) Excess organic solvents should be disposed of in the correct waste container. There is an organic solvents container for excess waste but there is another for halogenated organic solvent. 6) If there is a small fire you should try covering the fire with a fiberglass-wire gauze square, a big beaker, or a watch glass.

PreLab 8 1) Consider the mixed aldol condensation reaction of 1-(1-methylcyclopentyl)ethanone (shown below) and 2,2-dimethylpropanal (shown below) in the presence of sodium hydroxide. Provide the expected major MIXED aldol product for this reaction (answer could be in E or Z form) 2) In order to minimize forming a mixture of products in the reaction in the question above, which reactant would you use an excess of? Why? 3) Consider the mixed aldol condensation reaction of 1-(1-methylcyclopentyl)ethanone (shown below) and propiophenone (shown below). Two major MIXED aldol condensation poducts arise from this reaction (shown below, labeled A and B) If you wish to form product A, to which starting carbonyl would you add a strong base such as LDA in order to form the enolate? propiophenone Which carbonyl would you then add slowly to the enolate of the first carbonyl? 1-(1-methylcyclopentyl)ethanone

1) Image drawn 2) Use excess of 2,2-dimethylpropanol, because it has no alpha hydrogens 3) Propiophenone is the starting carbonyl needed to form product A, 1-(1-methylcyclopentyl)ethanone is added slowly to enolate of the first carbonyl

Sources of Error for MP Experiment

1) Moisture in the air ( which could have been absorbed by the sample) 2) Contamination of the sample 3) Uncalibrated thermometer in the Mel-Temp This is the only way for the melting point to have been higher than we would expect. It may also be lower if the thermometer is calibrated to a lower setting which leads to a shift in the range in the downward direction. 4) Determination made too fast 5) Criteria set for the experiment were not adhered to, including the filing of melting point capillaries.

Cengage MP 1) Under which circumstances is it appropriate to work in the laboratory alone? 2) Which of the following statements follow the rules for safety goggles in the lab? 3) If chemicals are spilled on the skin, your immediate action should be to... 4) Which of the following are good reasons for not leaving lids or tops off containers of chemicals once you have taken what you need? 5) When doing a melting point determination, if you miss the melting point you should: 6)Which of the following tend to have the higher melting points, organic compounds or inorganic compounds? 7) Flammable liquids will often have a stated flashpoint. What is meant by the flashpoint? 8) Glassware that is hot is potentially hazardous because it:

1) None 2) Safety goggles must be worn at all times in the laboratory. 3) wash the affected area with plenty of water. 4) It makes it more likely that contamination of one chemical by another will occur, Some chemicals readily absorb water from the air, and their composition changes. 5) allow the apparatus to cool and start again with a new sample 6) Inorganic 7) The lowest temperature at which the liquid has sufficient vapor pressure to ignite when in the presence of an ignition source 8) looks the same as unheated glassware

1) In the Dissolving the Solute step of crystallization, which of the following actions would reduce the percent recovery? 2) In the Crystallizing the solute step of Recrystallization, which of the following actions would reduce percent recovery of the solute (ignoring any unavoidable sources of error)? 3) In which step of crystallization would percent recovery go down if you did not use ice-cold solvent? 4) Which of the following could impact purity AND % recovery for recrystallization?

1) Not using solvent at boiling point to dissolve the solid (You want the solvent as hot as possible to ensure using the minimum amount of solvent) 2) Not placing crystal solution that has cooled to room temp in ice bath (Making the crystal solution as cold as possible maximizes % recovery) 3) Washing the crystals 4) Not drying crystals completely

PQ 9 - Epoxidation 1. Which of the following transformations is an oxidation? 2. The feature of cholesterol that provides some polarity to the molecule is: 3. Which species remains on the silica gel after the column chromatography is carried out? 4. Which is the only starting material in the epoxidation of cholesterol experiment that would show up under UV and which can only show up under I2? 5. Which is the only product in the epoxidation of cholesterol experiment that would show up under UV and which can only show up under I2?

1. 1 & 3 (addition of ester(o) & OH--> C=O) 2. The hydroxyl group 3. 3-chlorobenzoic acid 4. UV: MCPBA, I2: Cholesterol 5. UV: 3-chlorobenzoic acid, I2: cholesterol epoxide

PQ 8 - Aldol Condensation 1. This carbonyl, in the presence of a base (heat if needed), would react with itself and undergo: 2. Why would the carbonyl in the question above react as it does under the conditions listed in the question above? 3. If the two carbonyls above are mixed in equal amounts in the presence of NaOH under conditions to form aldol condensation products, what is the maximum number of products that could be formed? 4. The reason the reaction in the question forms the number of products it does is because: 5. If the two carbonyls above are reacted in the presence of NaOH under conditions to form aldol condensation products, what step would be best to promote the formation of only ONE major product?

1. Aldol addition 2. It has one a-H 3. 4 4. Both carbonyls can form enolates 5. Using excess B (no a-h)

PostLab 07 Esterification 1. The following lactone was formed in a intramolecular acid-catalyzed esterification of a hydroxy carboxylic acid. 2. What are the intensity of the IR absorption bands proportional to? 3. Why do the NaCl plates used for IR need to be handled with care? What precautions need to be taken when handling them? 4. Why are glass, quartz and plastics not used as IR sample holders? 5. Match the problems that arise when a particular situation is present when running a spectrum of a neat liquid: - Using a viscous liquid - Using low viscosity liquid 6. Which letter, in the diagram below, represents the location of the δ+ on an ester? In an ester, what circled feature in the diagram below, further increases the electrophilicity of the carbonyl carbon?

1. D (drawn in notebook) 2. The intensity of IR absorption bands is proportional to the change in dipole moment that a bond undergoes when it stretches. Each vibrational mode produces a peak in the spectrum because it corresponds to the absorption of energy at a discrete frequency. 3. NaCl plates used for IR need to be handled with care because they are fragile and are easily attacked by moisture, so they must be handled gently by the edges and kept away from moisture and aqueous solutions. Water should not be used to clean them because they can be dissolved. Methylene chloride is recommended for cleaning and nitrile gloves must be worn during this process. 4. Glass, quartz, and plastics are opaque to IR radiation and absorb it. Therefore, sample holders must be made of other transparent materials such as metal halide salts. 5. - Peaks are too intense - Weak peaks arise 6. C, 2

PQ 5 - Extraction 1. You wish to extract solute X from water. Solute X is equally soluble in organic solvents acetone and ethyl acetate. Acetone is miscible in water, ethyl acetate is immiscible in water. You choose: 2. You wish to extract solute X from water. Solute X is twice as soluble in diethyl ether as it is in methylene chloride. You choose: 3. Mixture X (pKa 5.67)+Y (pKa 9.24) in ether: H2CO3 pKa 6.52; H2O pKa 15 If NaHCO3 used: 4. Mixture X (pKa 5.67)+Y (pKa 9.24) in ether: H2CO3 pKa 6.52; H2O pKa 15 If NaOH used in extraction: 5. Mixture X (pKa 5.67)+Y (pKa 9.24) in ether: H2CO3 pKa 6.52; H2O pKa 15 If HCl used in extraction:

1. Ethyl acetate due to its immiscibility 2. Diethyl ether due X's greater solubility in it 3. Ionic form of X extracted into aq. layer (conjugate acid of NaHCO3 satisfy the criteria) 4. Ionic forms of X and Y extracted into aq. layer (Conjugate acid of NaOH satisfies the criteria for both species) 5. Nothing extracted into the aq. layer (acids d/n react with acids and bases d/n react with bases)

PostLab 06 Nucleo Sub 1. From observations in video and lab session: Which reactions undergo SN2 Which reactions undergo SN1 Which don't undergo either Compare these to theory in prelab 2. SN2: Rank fastest to slowest theoretically Explain theory with respect to: - structure of alkyl halide - leaving group 3. SN1: Rank fastest to slowest theoretically Explain theory with respect to: - structure of alkyl halide - leaving group 4. Explain theoretically why SN1 of 2-chloro-2-methylpropane with silver nitrate in ethanol/water would be faster than reaction of 2-chloro-2-methylpropane with silver nitrate in ethanol alone.

1. From observations in video and lab session: Which reactions undergo SN2 Based on the theory, reactions that contain strong nucleophiles in low concentrations should undergo SN2. SN2 reactions also typically include primary and secondary halides unless they are sterically hindered. Based on this, we should have seen 1-chlorobutane, 2-chlorobutane, 1-bromobutane, and 2-bromobutane undergo SN2. According to the lab video, only 1-bromobutane underwent SN2 Which reactions undergo SN1 Based on the theory, reactions containing tertiary and secondary halides should undergo SN1 due to steric hindrance. Based on this, we could have seen 2-chloro-2-methylpropane, 2-bromobutane, and 2-chlorobutane undergo SN1. According to the lab video, 1-bromobutane, 2-bromobutane, 2-chloro-2-methylpropane, and 2-chlorobutane underwent SN1 Which don't undergo either Based on the theory, aryl halides do not undergo either SN1 or SN2 due to the steric hindrance of the benzene ring. Bromobenzene is expected not to undergo either According to the lab video, bromobenzene did not undergo either so that is accurate 2. The theory states that the order of fastest to slowest SN2 reactions goes as such: 1-bromobutane > 1-chlorobutane > 2-bromobutane > 2-chlorobutane In regard to the structure and how it plays a part in the speed of SN2 reactions, the less steric hindrance the better. Reactivity is dependent on this and therefore we would expect primary halides to react faster than secondary ones In regard to the leaving group, faster SN2 reactions are based on this order: I > Br > Cl > F. In our case, Br is a better leaving group than Cl because it is a better leaving group. The better the leaving group the faster an SN2 reaction proceeds. This is the same for SN1. 3. The theory states that the order of fastest to slowest SN1 reactions goes as such: 2-chloro-2-methylpropane > 2-bromobutane > 2-chlorobutane In regard to the structure and how it plays a part in the speed of SN1 reactions, the more sterically hindered molecule, the better. The stability of the carbonation is taken into consideration and therefore tertiary halides proceed faster than secondary halides. In regard to the leaving group, faster SN1 reactions are based on this order: I > Br > Cl > F. In our case, Br is a better leaving group than Cl because it is a better leaving group. The better the leaving group the faster an SN1 reaction proceeds. This is the same for SN2. 4. Theoretically, SN1 of 2-chloro-2-methylpropane with silver nitrate in ethanol/water would be faster than the reaction of 2-chloro-2-methylpropane with silver nitrate in ethanol alone because.... Water as we learned is a polar protic solvent and when in the presence of ethanol, this pair becomes even more polar protic. In regard to SN1, polar protic solvents help to stabilize the carbocation, and the more stable, the faster the reaction proceeds. Considering the pair of water/ethanol results in better stabilizing, we expect that the SN1 of 2-chloro-2-methylpropane would be faster than if it were just in ethanol.

Cengage - Esterification 1. Which statement best describes how the system should be heated? 2. Which of the following is the best description of a reflux? 3. Which of the following is an appropriate use for reflux? 4. In the spectrum shown, which of the following peaks is NOT present? 5. IR spectroscopy can be used to determine which of the following? 6. Consider the reaction below. If you start with 2.0 moles of C3H8 and 2.0 moles of O2, what is the limiting reactant? C3H8(g) + 5 O2(g) → 3 CO2(g) + 4 H2O(g) 7. Ethanol (molar mass = 46 g/mol) can be dehydrated to yield ethene (molar mass = 28 g/mol) by heating it with an excess of concentrated sulfuric acid (acting as a catalyst). CH3CH2OH → CH2=CH2 + H2O If 14.97 g of ethanol produced 6.38 g of ethene, the percentage yield of the product is: 8. IR spectroscopy can be used to determine which of the following? 9. 1-butanol yields 1-bromobutane in the presence of concentrated sulfuric acid and an excess of sodium bromide. CH3CH2CH2CH2OH (l) → CH3 CH2CH2CH2Br (l) If 14.83 mL of 1-butanol produced 12.42 g of 1-bromobutane, the percentage yield of the product equals: (Assume the density of 1-butanol is 0.81 g/mL, the molar mass of 1-butanol is 74 g/mol, and the molar mass of 1-bromobutane is 137 g/mol.)

1. Heat gently so that the solvent boils and the vapors extend no more than half way up the condenser. 2. Reflux is a technique used to heat volatile materials. The reaction vessel is fitted with a condenser so that any vapors from the flask fall back into the heated mixture. 3. To carry out a reaction that needs heating 4. C=C 5. The presence of impurities in a product, the presence of certain bonds within a molecule, the absence of certain groups from a molecule. (Not molecular mass of sample) 6. oxygen 7. 70% 8. The presence of impurities in a product, the absence of certain groups from a molecule, the presence of certain bonds within a molecule 9. 57%

PQ 6 - Nucleo Sub 1. An alkyl halide undergoes SN1 rxn: which of the following will NOT increase rate? 2. An alkyl halide undergoes SN2 rxn: which of the following will NOT decrease rate? 3. Which of the following statements is true for BOTH SN1 and SN2? 4. Why is there no possibility of the E2 elimination product forming in the reaction of alkyl halide with sodium iodide in acetone? 5. Which of the following statements is true about the E1 reaction when alkyl halide is reaction with silver nitrate in ethanol?

1. Inc amount of solvent 2. Changing leaving group from Cl to Br 3. The rate-determining step involves the bondbraking of carbon and the leaving group 4. I- is a weak base and E2 reactions require strong bases 5. It occurs because both SN1 and E1 form the same intermediate

Cengage Recrystallization 1. Why does fluting a filter paper aid filtration? 2. What is the correct size of filter paper to use for a gravity filtration? 3. In a vacuum (Büchner) filtration, the correctly sized filter paper should 4. While using an ice bath, your reaction vessel accidentally topples over, allowing some ice water to enter it. You should, 5. In gravity filtration, the solution is filtered by pouring it into a folded filter paper in a filter funnel. 6. At the end of a reaction, water is added, and the desired compound precipitates. Of the following, which is the most appropriate way to isolate the compound from the solution? 7. An inexperienced chemist adds too little boiling solvent to an impure sample of product and then leaves this mixture to cool. The crystals 8. What happens to the crystal size if the impure crystals are dissolved in sufficient boiling solvent and then cooled on ice rather than in air? 9. In a recrystallization, the crystals do not always form spontaneously after cooling, even though the solution is supersaturated. Which of the following will help crystals form? 10. Which of the following describes the technique for recrystallizing a compound? 11. Which of the following statements is true when considering temperature during a recrystallization? More than one answer may be correct. 12. Why is it necessary to use the minimum amount of solvent when doing a recrystallization?

1. It decreases the contact area between liquid and glass to increase the speed of filtration. 2. Small enough so that the top of the filter paper sits a couple of millimetres below the rim of the filter funnel. 3. Just cover the bottom of the Büchner funnel. 4. stop the procedure and speak to your instructor about how to proceed. 5. This procedure is generally used to remove solid impurities from a solution or liquid product. 6. Filter the whole volume by Büchner filtration. 7. form with product coated onto impure crystals. 8. The crystals produced are smaller when ice cooled 9. Add some crystals of the compound you are trying to crystallize, Scrape the inside of the Erlenmeyer flask with a glass rod below the surface of the solvent. 10. Dissolve the sample in the minimum amount of boiling solvent and then allow to cool. 11. Ideally the hot solvent used will keep the impurities dissolved OR not dissolve them at all, it is important that the sample is dissolved in just enough hot solvent. 12. To maximize the yield of product.

PreLab 09 - Epoxidation 1. Why can you not selectively epoxidize an alkene with MCPBA in the presence of a ketone? 2. Compare and contrast the travelling of eluent in TLC versus column chromatography. - TLC: Solvent ________ the plate by ________ -Column chromatography: Solvent ________the column filled with adsorbent 3. What happens to form the brown spots on a TLC plate when you place the developed TLC plate in an iodine chamber?

1. Ketone will be converted to an ester 2. Rises up, capillary action, flows 3. Certain compounds such as alkanes, alcohols, and ethers, do not absorb UV light sufficiently to quench the fluorescence of the TLC plate and therefore will not show up under a UV light. However, they will adsorb iodine vapors and can be detected by placing the plate for a few minutes in a capped bottle containing some crystals of iodine. Iodine vapor is adsorbed by the organic compound to form brown spots.

Cengage Extraction 1. At the end of a reaction it is important to remove the solvent from a solid product (more than one answer may be correct) 2. Which of the following methods is suitable for evaporating 5 mL of solvent? 3. The appropriate method for removing a solvent depends on: 4. The rate of evaporation can be increased by: 5. When adding drying agent, how do you know when you have added enough? 6. An aqueous solution is being extracted with chloroform (trichloromethane). Which layer is on the bottom of the separatory funnel? 7. When performing a microscale extraction using a conical vial, always extract the: 8. Which is the best description of how to dry a liquid with a drying agent? 9. In a microscale solvent extraction, the densities of the two liquids determine whether the organic solvent is the top layer or the bottom layer. Using the table of densities, determine whether chloroform is the top layer or the bottom layer when used with water. 10. What is the purpose of venting the extraction vial 11. How should the drying agent be removed at the end of the drying procedure? 12. Why are the anhydrous forms of the salts used?

1. So that the yield can be determined, so that the melting point can be determined, so that clean NMR spectra can be obtained that do not contain solvent peaks 2. Heat the solution in an Erlenmeyer flask using a water bath and hot plate, reduce the pressure using a vacuum source and vacuum flask, leave the solution in an open flask in the fume cupboard. 3. The volume of solvent being evaporated, the hazards associated with the solvent, the volatility of the solvent, the thermal stability of the product 4. Increasing the surface area to volume ratio, increasing the temperature, decreasing the pressure. 5. The powder no longer forms clumps. 6. Chloroform 7. Bottom layer first. 8. Add the drying agent in small batches and observe the solution between each addition. 9. Bottom layer (it is denser than water, Chloro = 1.5 g/ml, water = 1.0 g/ml) 10. To relieve built up pressure from gases produced or from solvent vapor formed. 11. The drying agent can be filtered out, the liquid can be decanted into another container. 12. The anhydrous salt has the capacity to absorb water to form the hydrated salt.

PreLab 06 Nucleo Sub 1. Define steric hindrance in a nucleophilic substitution reaction. 2. In theory, which alkyl halides that you are using in the experiment undergo SN2 reactions? Which alkyl halides that you are using in the experiment undergo SN1 reactions? Which alkyl halides that you are using in the experiment don't undergo SN2 or SN1 or both reactions?

1. Steric Hindrance in a nucleophilic substitution reaction is defined as the ease with which the nucleophile can come within bonding distance of the alkyl halide. 2. Based on the theory, the alkyl halides that we will be using in the experiment that undergo SN2 reactions include: Primary alkyl halides: 1-chlorobutane, 1-bromobutane Reactivity of structure; 3˚<2˚>1˚<CH3 Based on the theory, the alkyl halides that we will be using in the experiment that undergo SN1 reactions include: Tertiary alkyl halide: 2-chloro-2-methylpropane Benzyl halide Reactivity of structure; 3˚>allyl~benzyl~2˚>1˚>CH3>vinyl Based on the theory, the alkyl halides that we will be using in the experiment that do not undergo SN1 or SN2 reactions include: Vinylic and Aryl Halides However, according to theory, 2˚ Alkyl halides may undergo both Sn1 & Sn2. The halides that fall under this category include: 2-chlorobutane & 2-bromobutane, bromobenzene does not undergo either, no alpha carbons, A benzyl halide has an extra carbon between the benzene ring and the halide, so it has an alpha carbon

LQ 10 1. In the synthesis of meso-hydrobenzoin that you carried out, what expected observation would you NOT observe had you not added the 2nd amount of water to the reaction mixture? 2. A solvent pair is used in partial recrystallization in the synthesis of dibenzalacetone. Which is the better solvent? When would it have been added in a traditional recrystallization with a solvent pair? 3. a) The use of ice when reacting benzil with NaBH4 contributed toward the purity of the product formed by: minimizing formation of side product b) Which of the choices for Answer 2 would primarily contribute toward purity of crystals in the recrystallization process? Wrapping test tube with hot solution with paper towel LQ 09 1. Indicate for each of the scenarios if the action is desirable or undesirable when carrying out a TLC for epoxidation: Using 2 mm high of eluent in chamber Leaning TLC plate on filter paper Making sure TLC plate is level at the bottom of developing chamber 2. 3. LQ 08 1. The melting point of dibenzalacetone is 110-111°C - how many degrees below the lower range shown should you slow down the rate of the heating of the melting point apparatus? 2. The starting materials of dibenzalacetone synthesis are all colorless. Which situation would have caused no change in color of the reaction mixture? 3. Match the undesirable outcome with the scenario that causes that particular outcome. Oily product during recrystallization Crystal solution of dibenzalacetone not saturated Loss of product during reaction

1. The formation of white crystals 2. Ethanol, first 3. a) minimizing formation of side product b) Wrapping test tube with hot solution with paper towel LQ 09 1. Undesirable, undesirable, desirable 2. 3. LQ 08 1. 20 degrees below 2. 3. -Dibenzalacetone solid not washed prior to recrystallization -Hot 70:30 ethanol/water solvent not added dropwise to dibenzalacetone solid -Allowing leakage while reaction mixture for dibenzalacetone synthesis was shaken

Cengage TLC 1. Why shouldn't the start line, where the solution mixtures are initially placed, be drawn in ink? 2. When setting up a column, what is the reason for adding a layer of sand on top of the adsorbent column? 3. What is a good R f value in order to ensure that a compound will elute over a reasonable timeframe? 4. What can you do to elute a compound that is not coming off the column? 5. In silica gel chromatography, which compounds elute first? 6. Which of the following statements about the procedure for column chromatography are true? 7. What is the reason for the layer of sand at the bottom of the column?

1. The ink is likely to dissolve in the solvent and will add extra spots to the chromatogram. 2. To prevent disruption of the surface when solvent is added 3. Around 0.3 4. Change to a more polar solvent 5. The least polar 6. Apply enough pressure to increase the flow rate to a reasonable degree, check for cracks in the glass before pressurizing the system. 7. To prevent the adsorbent from passing through to the tap

PostLab 8 1. In the citric acid cycle when an aldol addition occurs in a biological system, how do the amino acids contained in the Citrate Synthase enzyme help facilitate the reaction? 2. What is the order of reagents that were added to the test tube used to carry out the synthesis of dibenzalacetone? 3. An amount of the dibenzalacetone crystals formed are recrystallized using 70:30 ethanol/water solution. What are the next 2 immediately sequential actions AFTER a boiling stick is added to the test tube once a few drops of solvent is added to the solid? (Don't skip steps) 4. a) Why would the presence of the side product benzalacetone be minimized? b) Why would the presence of the side product 4-hydroxy-4-methyl-2-pentanone be minimized? 5. Where do the following items need to be disposed of when carrying out the experiment: -Melting Point Capillary - Disposable Test Tube - Pipette - Excess Solvent - Used Paper Towels

1. They protonate and deprotonate 2. NaOH, Benzaldehyde, then acetone in ethanol 3. Step 1:Heating solution with boiling stick while adding hot solvent until solid is dissolved Step 2: Removing boiling stick 4. a) The presence of the side product benzalacetone will be minimized in our synthesis in this experiment because we will run our reaction to completion. This side product is produced primarily when we have an incomplete reaction. b) The presence of the side product 4-hydroxy-4-methyl-2-pentanone would be minimized in this synthesis reaction because our starting carbonyls are not conjugated. This product does not spontaneously form alpha, beta-unsaturated ketones without heat. 5. - Sharps - Broken Glass container - Sharps - Solvent/liquid waste - Regular trash

PQ4 - TLC 1. All spots move to top of TLC plate even though you used appropriate solvent. You: 2. All spots remain on the bottom of TLC plate on appropriate adsorbent. You: 3. If developed spots are not visible after proper developing and visualizing techniques were carried out, the error in technique that occurred during the SPOTTING stage is: 4. If developed spots are not visible after proper spotting and visualizing techniques were carried out, the error in technique that occurred during the DEVELOPING stage is: 5. You spot a sample of X on silica and develop it using ethyl acetate. The sample travelled 6.0 cm while the solvent travelled 10.0cm. If you spot another sample of X on another silica plate and develop it using ethyl acetate, what is likely to be the distance the sample travelled if the distance the solvent travelled is 8.0 cm?

1. Used silicia for very nonpolar compounds 2. Used too nonpolar a solvent compared to samples 3. Spotted sample non concentrated enough 4. Solvent above the spotting line 5. 4.8 cm

PQ 7 - Esterification 1. Which of the following will NOT shift equilibrium towards formation of ester? 2. If you had used a traditional acid to carry out the esterification reaction, what role does the following species play in a subsequent step? - Sodium carbonate 3. If you had used a traditional acid to carry out the esterification reaction, what role does the following species play in a subsequent step? - Ether 4. If you had used a traditional acid to carry out the esterification reaction, what role does the following species play in a subsequent step? - Saturated Sodium chloride 5. If you had used a traditional acid to carry out the esterification reaction, what role does the following species play in a subsequent step? - Calcium chloride pellets

1. Using wet glassware (adding excess of cheaper starting mat & removing water WILL) 2. Neutralize excess acid 3. Extraction solvent 4. Remove water from organic layer 5. Remove water from organic layer

Cengage Distillation 1. When setting up a fractional distillation, the main difference from a simple distillation is: 2. When performing a distillation, the collection end should be in some way open to the atmosphere. 3. A liquid is said to be boiling when: 4. Which is the best description of a fractional distillation? 5. Under what circumstances is vacuum distillation used? More than one answer may be correct. 6. You are required to separate a mixture of two solvents. One has a boiling point of 45°C, and the other has a boiling point of 120°C. Which of the following is the most appropriate type of distillation to use? 7. Two liquids have boiling points which are less than 20 °C apart. How can a simple distillation be modified to improve the separation? 8. What is the key benefit of using vacuum distillation? 9. When performing a distillation, how can you tell when your liquid is beginning to distill over? More than one answer may be correct. 10. A mixture of two immiscible liquids will always boil at a temperature: 11. Which of the following is true about distillation boiling point determination? More than one answer may be correct. 12. Which of the following is an appropriate use for distillation apparatus? 13. A liquid is said to be boiling when: 14. What happens as the temperature of a liquid is increased? 15. Predict the trend in boiling points for the following compounds (1 being the lowest boiling point). 16. Which of the following factors affect boiling point? 17. Which of the following mixtures would be suitable to separate by steam distillation?

1. You need to add a column between the flask and the distillation head. 2. True 3. The vapor pressure of the liquid is equal to the atmospheric pressure. 4. A technique to separate liquid mixtures with boiling points close to each other. 5. When the liquid reacts with oxygen in the air at high temperatures, when the boiling point of the liquid is high, when the compound is thermally unstable. 6. Simple 7. Use a fractionating column 8. It allows you to distill liquids that may degrade when heated above a certain temperature. 9. Liquid droplets start to condense on the thermometer bulb, the temperature remains constant after initially rising. 10. Below the boiling point of both of the components of the mixture when pure. 11. The sample should be as pure as possible before boiling point determination, the thermometer should be positioned so that the temperature of the vapor is measured. 12. To remove a liquid product from a reaction mixture, to measure a boiling point of a liquid. 13. The vapor pressure of the liquid is equal to the atmospheric pressure. 14. On average the molecules have more energy, more molecules escape to the gaseous phase, increasing the vapor pressure. 15. Water-4, Pentane-2, Ethanol-3, Iso-pentane-1, sodium n-butoxide-5 16. Whether a compound is polar or not, the pressure. 17. A mixture containing large organic molecules, a mixture containing thermally unstable organic molecules

Prelab 10 - Reduction 1. Pure R,R-hydrobenzoin (side product of meso-hydrobenzoin) has a melting point of 148°C. a) What do you expect the melting point of pure S,S-hydrobenzoin (another side product of meso-hydrobenzoin) to be? b) Do you expect the racemic mixtures of these enantiomers to have the same or different melting points as the pure enantiomers? 2. Indicate if each of the following reactions are an Oxidation, a Reduction, or a Substitution: 3.If you had carried out a TLC on the reaction mixture in this experiment, you would have used a 2:1 mixture of hexanes/ethyl acetate as your eluent. a) From Table 8.3 in the TLC chapter, is your eluent made up of mostly polar or nonpolar solvent? b) From the the TLC background and theory lecture, besides proper balance of polarity, what is the requirement for the pair of solvents? c) You are using 2:1 hexanes/ethyl acetate to develop the TLC plate and measure the distance the sample(s) travelled. Would the distances travelled by the sample(s) increase or decrease if you: - added more ethyl acetate to the eluent - added more hexanes to the eluent

1. a) 148 degrees b) different 2. 1) Reduction 2)Substitution 3) Oxidation 4) Reduction 3. a) Nonpolar b) miscible c) Increase, decrease

Where do the following items need to be disposed after carrying out the melting point experiment? A) Melting Point Capillary (after use) B) Disposable Test Tube C) Used Weighing Paper D) Leftover Solid Organic Compound

A) Sharps Container B) Broken Glass Container C) Regular Trash D) Solid Chemical Waste

How was the identity of your unknown confirmed? (MP Experiment where M-Toluic Acid is the unknown)

Confirmed by the measuring of the melting point of the unknown and the m-toluic acid standard. I was told that the unknown is indeed the alphabetically second stand which I picked and if this was mixed with my unknown that would mean that I would be mixing m-toluic acid with more m-toluic acid. The melting point/range will stay the same if there a no impurities present and because once substances are deemed pure, the melting range is the same across every test of that substance. If they were different, we would then see a change in the melting range which would lead me to believe a mixture was taking place.

What is the definition of efficient stacking when it pertains to how molecules stack depending on the shape of the molecule? How does efficient stacking ensure a higher melting point?

Efficient stacking refers to the ability molecules have to pack tightly into a crystal lattice. Molecules such as saturated fats have a more regular shape and therefore stack better with other saturated fats when compared to unsaturated ones which have irregular shaping and kinks in their structure. Better stacking maximizes van der Waals forces which in turn increases the amount of energy needed to separate these tightly packed molecules and therefore increases their melting point as well.

Define the term separation it relates to general chromatography. What is the purpose of having very small bores on the spotters? Besides a large spot and the TLC sample being too concentrated, what two other factors can cause the developed spots to appear as a streak? Other than solubility of sample in the solvent, what is the criteria for the solvent (other than cheap and nontoxic) used for preparing the sample that impacts the experiment and why would this criteria be important in the spotting phase if you have to make repeated applications of the sample? In what case would column chromatography be used to purify a desired compound because techniques like recrystallization, extraction and distillation are not adequate to do so? Why would water not be used to elute a column (besides it polarity) in column chromatography? In column chromatography (microscale), after loading it with solvent and adsorbent and prior to loading the sample, what level should you allow the solvent to drop to? Why should you not allow the sample to run dry and what is the consequence if you had allowed it to do so? Rank standards from Plate from Least to Most Polar (Based on TLC) Let's consider that ethyl acetate is the ideal solvent for this TLC experiment. What might have happened to the spots if you had used t-butyl methyl ether as the eluent instead of ethyl acetate. Why? Let's consider that ethyl acetate is the ideal solvent for this TLC experiment. What might have happened to the spots if you had used acetone as the eluent instead of ethyl acetate. Why? Cyclohexene is dihydroxylated in two different manners to form 1,2 -cyclohexanediol. One method forms the cis-diol and another forms the trans-diol. The TLC plate featuring the two different diols was developed with ethyl acetate and then stained with p-anisaldehyde for visualization purposes - see below:

In the context of general chromatography, separation is defined as a measure of the elution or migration rate of compounds. This process of removing two or more compounds/ions from another caused by their molecular interactions between two phases (one moving and one stationary). The purpose of having very small bores on the spotters is to ensure that once the liquid is drawn up, it will not flow out to form a drop. Streaking as stated, maybe the result of the sample being overly concentrated, but two other factors that may result in the same streak are 1) if a sample contains many components, the spots may just run together and appear as a streak and 2) some solvents also can cause pure compounds to streak. Other criteria include having a low boiling point and having low viscosities. The lowered BP allows for easy evaporation, while the low viscosity allows for better migration. Compounds that are too similar Water isn't used in column chromatography typically because it may result in the destruction of the stationary phase's integrity by dissolving the silica gel. You should allow the solvent to drop to around the top of the packing. You should not allow the sample to run dry, because this allows for the creation of air bubbles and channel formation. These outcomes are the most conducive to separation and cause it to be poor. Least Polar: aspirin, 2nd Most polar: acetaminophen, Most Polar: caffeine Spots remain towards bottom of TLC plate --- t-butymethyl ether less polar, cannot overcome attractions of sample to adsorbent Spots move towards top of TLC plate --- acetone more polar, overcomes attractions of sample to adsorbent better The reason the TLC could not be visualized by UV is because: The products are not conjugated, The reagents 1) Oxone, acetone 2) H3O+ forms the more polar diol - what is the product? cis-diol

The distribution coefficient between methylene chloride and water for solute Y is 15. An amount of 80.0 g of Y is dissolved in 190 mL of water. a) What weight of Y would be removed from water with a single extraction with 190-mL of methylene chloride? Show calculations and report to 1 decimal place. b) What weight of Y would be removed from water (the original solution) with two successive extractions with 95-mL portions each of methylene chloride? Show calculations and report to 1 decimal place. You have 141.0 g of solute Q dissolved in 150-mL of water. The distribution coefficient between ether and water for solute Q is 8. What volume of ether would you need to extract 101.0 g of solute Q in one extraction from the original 141.0g dissolved in 150 mL water? Provide answer to closest mL. (Show calculations) Purity implications from melting points

K = ([C] in organic solvent) / ([C] in water) C = solute K=15 for solute Y a) 15 = (x/190) / ((80-x)/190) ---> 15((80-x)/(190)) = x/190 ---> (1200-15x)/190 =x/190 /190 cancels out ---> 1200-15x = x ---> 1200 = 16x x = solute in organic solvent = 75.0 g after the first extraction Initial weight was 80.0g and the amount extracted was 75.0g --->80-75= 5.0 g removed from water b) 15 = (x/95) / ((80-x)/190) ---> 15((80-x)/(190)) = x/95 ---> 95(1200-x)=190x cancels out ---> 1200-15x = 2x ---> 1200 = 17x x = solute in organic solvent = 70.59 g after the first extraction 15 = (x2/95)/ ((9.4 - x2)/190); x2 = 8.3 . Now 8.3+70.6 = 78.9g extracted after 2nd extraction K = ([C] in organic solvent) / ([C] in water) C = solute K= 8 for solute Q 8= (x/y) / ((141-x)/150 ) We know x is 101.0 of solute Q. Substitute this in and we get ---> 8= (101.0/y) / ((141-101)/150) 8= (101.0/y )/(40/150) ---> 8= (101.0/y) /0.26666 ---> 0.26666 (8) = 101.0/Y ----> 2.1333y =101.0 Y= 47.34 ml of ether needed to extract 101.0 of original solute via one extraction. Based on the MPs given after conducting the experiment, I am able to conclude that the solid recrystallized is mostly pure. The range of all three solids is within 1-2˚C and this is a sign of a pure substance. There may be other factors that can affect the purity, but solely based on MPs, they seem to have little to no impurities.

In the solvent pair experiment that is being carried out with the solid that is being recrystallized, why do you NOT have to worry about sudden vigorous boiling of crystal solution when you add the second solvent to the solution?

You do NOT have to worry about sudden vigorous boiling of crystal solution when you add the second solvent to the solution because if you follow the experimental procedure, you will know whether the second solvent has a lower or high boiling and proceed accordingly. If the second solvent has a higher boiling point you don't have to worry about the bumping because it won't become superheated considering the temperature hasn't reached that point. However, if you are working with a 2nd solvent with a lower boiling point, you can lower the temp of the solution slightly before adding it to prevent vigorous boiling. A wood applicator stick can also be added to the solution as well as boiling chips can be added to prevent this process of bumping.

The solubility of solid W in water is: 1.93 g/100 mL at 0°C, 21.5g/100 mL at 100°C. How many mL of boiling water are required to dissolve 151.0 g of W?(report to the nearest mL) If solution were cooled to 0°C, how many grams of W would crystallize out? (report to one decimal place) What is the percent recovery? (report to one decimal place) (Show calculations)

You would need 702.32 or ~702 mL of boiling water to dissolve 151 grams of solid W. If the solution was then cooled to 0˚C, you would witness 13.55 or ~13.6 grams of W crystallizing out. The percentage recovery is 92.03 or ~92.0%. Calculations: 151.0 g W x (100mL/21.5 g) = 702.325 mL --> ~702 ml 702.325 mL x (1.93 g /100mL) = 13.55 --> ~13.6 g of W ( (151.0 g -13.55 g )/ 151.0 g ) x 100 = 92.03 ---> 92.0%

PreLab 07 Esterification In the synthesis of isobutyl propionate (shown on pg. 521), excess propanoic acid is used in the reaction. a) What purpose does the excess acid serve? b) What does this indicate with regards to the relative costs of the two starting materials in this synthesis?

a) The excess acid serves to drive the reaction forward. The excess propanoic acid as we learned this week will allow the formation of isobutyl propionate (product in this reaction). b) I believe excess acid driving the reaction towards the formation of product demonstrates Le Chatelier's principle. By increasing one of the reactants/starting compounds, we can make the reaction go towards the creation of its major and minor products. In regard to this synthesis, we know that propanoic acid requires 148 mg while 2-methyl-1-propanol only requires 112 mg. From this we can infer that the limiting reagent is 2-methyl-1-propanol and therefore, propanoic acid should be the cheaper starting material.

You are given a unknown white solid to recrystallize in lab. The white solid could be Compound A (melting point 160-162°C), Compound B (melting point 110-111°C) or Compound C (melting point 141-142°C). Compound A, B and C are significantly soluble in n-butanol (bp: 125°C), even at room temperature and not very soluble in water (bp: 100°C) or ethanol (bp: 78°C) (difference in solubility of solid in water and ethanol is not significant) . N-butanol is miscible with ethanol but not with water a) If you decide to use n-butanol (must use this solvent) and choose between ethanol and water as the solvent pair for the unknown white solid, describe which solvent you would heat up and dissolve the solid in initially ________ and which solvent you would add second ________ and at what point would you stop adding the second solvent ________ b) if you could use n-butanol as the single recrystallization solvent for the solid, which compound might have a problem of oiling out?

a) hot n-butanol, ethanol, first signs of cloudiness b) B

The crystallization step of recrystallization removes which category of impurities? The washing step of recrystallization removes which category of impurities?

within the crystal lattice on the surface of the solid

The fast determination of the first sample of your unknown shows the unknown melting around 112(C). A) At what temperature should you slow down the rate of heating to 1(C)/min? B) You have to pick two standards that could be your unknown because you don't know if thermometer calibration is an issue - the first standard MUST be listed alphabetically before the second standard. C) If your unknown is indeed the alphabetically second standard that you chose, what would happen to the mixed melting point of your unknown +this standard? D) Based on the result above, what would happen to the mixed melting point of your unknown + the alphabetically first unknown that you picked? E)What is the identity of your unknown?

A) 92 ˚C (Slow down ~20˚C before range) B) Acetanilide + M-Toluic Acic C) Melting Point Stays the Same D) Melting Point Goes Down E) M-Toluic Acid

Where do the following items need to be disposed of after carrying out the melting point experiment? A) Glass pipette after use B) Disposable Test tube C) Used filter paper D) Ethanol filtrate

A) Sharps Container B) Broken Glass Container C) Regular Trash D) Solvent/Liquid Waste

Why would boiling stones not be able to control the bumping of liquids in vacuum distillation as they are able to for simple and fractional distillations? Since boiling stones cannot be used to control the bumping of liquids in vacuum distillation, other methods are used. What is specifically done with glass wool (one of the implements used to control bumping) when small quantities of material are being distilled via vacuum distillation? What aspect of water makes it favorable to use in steam distillation?

Boiling stones are not able to control the bumping of liquids in vacuum distillation as they are able to for other forms of distillation because they lose their activity in an evacuated system. Another method used to prevent bumping when small quantities of material are being distilled is to introduce sufficient glass wool into the flask. The introduction of glass wool is done in order to fill a part of the space above the liquid. Its low molecular weight

Liquid Mixture: 75% P (bp 60°C) and 25% Q (bp 100°). Why can you purify with fractional distillation? Liquid Mixture: 95% P (bp 60°C) and 5% Q (bp 100°). Why can you purify with simple distillation? How do you maintain the temperature gradient in a fractional column? How do you avoid having a flooded column in a fractional distillation? Which of the following represents the source of error that is unique to fractional distillation that explains why not all liquid would be recovered in a distillation?

Both BP difference and composition Composition Don't distill too fast Don't distill too slow Hold up

Calculate the mole fraction of A (XA) in the vapor if a mixture of liquids is 69%A and 31%B. The vapor pressure of pure A (PA∘∘) is 783 torr and the vapor pressure of pure B (PB∘∘ is 796 torr. Show calculations and give answer to 2 decimal places. The mole fraction of B (XB) in the vapor of a mixture of A and B is 0.62 and the sum of the partial pressures of A and B is 780 torr. Calculate the mole fraction of B (Nb) in the liquid if the vapor pressure of pure B (PB∘∘) is 727 torr. (Hint: Find PB first) Show calculations and give answer to 2 decimal places (if not reporting as a percentage):

Mole fraction of A(Xa) = Pa / Ptot Pa=Pa˚(Na) ---> (783 torr)(.69)= 540.27 Pb=Pb˚(Nb) ---> (796 torr)(.31)=246.76 Ptot=Pa+Pb ----> 246.76+540.27=787.03 A(Xa)= (540.27)/(787.03)= .686 ~.69 B(Xb)=0.62 Ptot=780 torr B(Pb˚)=727 torr B(Xb)=(Pb)/(Ptot) --->Pb=(Ptot) (B(Xb) ---->780 torr (.62) = 483.6 = Pb Pb=Pb˚(Nb) ----> 483.6 torr = 727torr (Nb) ----> 483.6/727 = .665 ~ .67

Pure Compound X has a melting range of 128-129°C. If you perform a melting point determination of a sample of compound X and find that it melts with a range of 119-129°C, which of the following WOULD NOT be the reason you see this result?

Sample has a soluble impurity (It would widen range AND depress upper range)

You come across a white solid and take its melting point and find it to be 104-107°C. You decide to identify it. If the thermometer is calibrated, compounds of what general melting point range can you automatically eliminate and why?

The general melting point you can automatically eliminate is anything with a melting point below 104˚C (our lower range of MP) because the only way for a wider range and lower MP would be through impurities. Assuming that we are looking for a pure substance, we would not want to go lower than our expected range.

You dissolve an amount of solid Q in 213.0 mL solvent, forming an unsaturated solution. The solubility of Q at 0°C is 1.81 g/100 mL. The amount of solid remaining in solution at 0°C is 21.0% of the original amount of solid dissolved . What is the original amount of solid that was dissolved (report to 1 decimal place)?

The original amount of solid that was dissolved according to my calculations is 18.358 g or approximately 18.4 g. Calculations: 213.0mL x (1.81 g/100mL) = 3.8553 3.8553 is 21% of original amount 3.8553/.21= 18.358 ---> ~18.4 g

Toluene (shown below) would have a lower melting point than benzene (shown below) even though it has higher molecular weight. Why?

Toluene does not pack as tightly as benzene in a crystal lattice and does not have as many Van der Waals forces

What is the character of the vapor after each condensation-vaporization cycle in a fractional distillation of a mixture? What specifically causes the vaporization of the lower boiling liquid on the packing in a fractional distillation? Explain the adiabatic process as it specifically pertains to a fractional distillation.

Vapor is richer in the more volatile fraction The packing material used in fractional distillation is responsible for providing increased surface area for the heat exchange between the ascending vapor and the descending liquid, this results in multiple condensation/vaporization reactions to occur in the column and the vapor ascends. The condensing of the higher boiling point vapor releases heat, which causes vaporization of the lower boiling liquid. The most important variable that contributes to successful fraction distillation is the rate at which the distillation is carried out. When a series of simple distillation takes place within the fractioning column, it is important that complete equilibrium is achieved between the ascending vapors and the descending liquids. Considering this process isn't instantaneous, heat should be transferred from the ascending vapor to the descending liquid without a gain in heat or net heat loss to surroundings, therefore making it adiabatic

You have a mixture of 2-chlorobenzoic acid (pKa 2.92) and 4-Bromophenol (pKa 10.2) dissolved in ether. You will need the following information: The pKa of HCl is -7; pKa of carbonic acid (H2CO3) is 6.52 and the pKa of water is 15. a) Which species do you use to separate the mixture? b) Which species will remain in the ether layer?

a) Sodium bicarbonate b) 4-bromophenol

Para-Cyanobenzoic acid has a pKa of 3.55. 2-Chlorophenol has a pKa of 8.56. 4-Nitrophenol has a pKa of 7.15. You will need the following information: The pKa of HCl is -7; pKa of carbonic acid (H2CO3) is 6.52 and the pKa of water is 15. Mixture A is a mixture of 2-Chlorophenol and 4-Nitrophenol. Mixture B is a mixture of Para-Cyanobenzoic acid and 2-Chlorophenol. Mixture C is a mixture of Para-Cyanobenzoic acid and 4-Nitrophenol. All mixtures are dissolved in methylene chloride a) Why would reacting Mixture A with an aqueous solution of NaHCO3 (sodium bicarbonate) NOT separate one substance from the other? b) Why would reacting Mixture B with an aqueous solution of NaOH (sodium hydroxide) NOT separate one substance from the other? c) What species (among HCl, sodium hydroxide and sodium bicarbonate) could you use to separate the components of Mixture C? d) What species would exist in the aqueous layer AFTER the extraction?

a) The acidity of carbonic acid is stronger than both components so neither will be extracted into the aqueous layer b) The acidity of water is weaker than both components so both will be extracted into the aqueous layer. c) Sodium bicarbonate d) Sodium salt of para-cyanobenzoic acid