Lab Final (Spinach Lab on)
Which of the following wavelengths of light is the highest in energy? 250 nanometers 3 centimeters 400 micrometers 450 nanometers
250 nanometers smaller the better
How many proton NMR signals will be observed for 3-methyl-2-butanone
3
Spinach Lab Polar compounds interact more ______ with the stationary phase, so they travel a _______ distance up the plate. Therefore, the Rf values for polar compounds are ______.
strongly shorter Small
How do you calculate the % yield. How do you calculate the theoretical yield? (in grams)
(actual yield)/(theoretical yield)= percent yield x 100 moles of limiting reagent X molecular weight of product
In case of a chemical splash to the eyes, how long should you rinse your eyes in an eyewash station? 5 minutes 10 minutes 15 minutes
15 mins Even if your eyes feel better, you need a full 15 minutes of irrigation to fully flush a chemical from your eyes. This goes the same for a spill on your skin, too. Don't skimp on this!
Where is carbonyl located on IR spectra?
1700 wavenumber 10 transmittance
Safety is taken very seriously in the organic laboratory, and unsafe behaviors, such as removing safety glasses or eating/drinking/chewing gum in the lab, are not tolerated. Match the violation below with the resulting penalty: 1st penalty: warning, grade deduction, sent home for the day 2nd penalty: warning, grade deduction, sent home for the day 3rd penalty: warning, grade deduction, sent home for the day
1st penalty: warning 2nd penalty: grade deduction 3rd penalty: sent home for the day
Where is OH stretch on spectra of IR?
3200-3600 25% transmitance
Where is an Amine located on spectra of IR?
3200-3600 70% transmitance
Degrees of unsaturation (2C + 2 + N - H - Halogens)/2 C8H11NO2 has _______degrees of unsaturation
4
A compound with the molecular formula C7H14O gives the proton NMR spectrum shown below. An IR of this same compound shows a strong signal at 1720 cm-1. Based on this information, determine the structure of this molecule. What is the IUPAC name of the molecule? Remember to report the answer with proper notation. The IUPAC name is _______________ .
4,4-dimethyl-2-pentanone
Spinach Lab Consider the following TLC plate, developed in ligroin. Calculate the Rf values of A, B, and C. Which compound is the most polar? How would the Rf values change if a more polar solvent (like ethyl acetate) were used? (Solvent front is 8 cm) ___________________________ solvent line o----------6.4 cm ---------o-5.3 cm ----o------2.1 cm A B C Origin is 0 cm
A Rf = (6.4 cm/8 cm) = .8 B Rf = (2.1 cm/8 cm) = .26 C Rf= (5.3 cm/8 cm) = .6625 b) (B) has the lowest Rf value, therefore it is the most polar. c) The more polar the solvent, the greater its capacity to carry components with it, taking the components further away from the origin, increasing Rf values.
What is emulsion? How much should you fill seperatory funnel? Can you clean it? What do you do if you see any water in the organic layer during an extraction?
An emulsion happens when tiny droplets of one liquid become suspended in another. Add brine or gently swirl the liquid in the funnel. Only fill it two-thirds full. Clean with soapy water and let it dry. Yes clean it. Remove the aqueous portion before you add the drying agent since the only way drying agents are used are for drying organic liquids.
Can IR spectroscopy be used to distinguish 2-pentanone from 2-hexanone? Why or why not?
Both compounds would show nearly identical IR spectra due to the carbonyl C=O stretch and alkane C-H stretch in both molecules
Making Polymers Lab Polystyerene is created by ______ addition polymerization. How does a chain polymerization work? How does a condensation polymerization work? How do they differ? (chain vs condensation polymerization) Slime is a _______-_______ ________. Extra info: Slime will stick to carpet, clothing, and hair. Nylon we create in lab is NOT SAFE to take home. Polymers are EVERYWHERE in our lives.
Chain addition polymerization. Chain addition polymerization involves the use of an initiator that forms a reactive species. A radical is formed, then radicals react with the styrene monomers to begin the chain addition process. Condensation polymerization works by two monomers react to form a larger unit while H2O or HCl is lost. Chain: vinyl-type monomer simple hydrocarbon backbone functional group is pendant to the polymer chain Emperical formual is identical to that of the monomer Condensation: Functional groups are part of the polymer backbone Formed as the monomer units link together small molecule is produced as two monomer units linked together, different emperical formulas for monomer and polymer. Cross linked polymer. Gives an elastic gel.
Spinach Lab How do you explain the difference in polarity of the two chlorophylls in your sample?
Chrlorophyl b has the extra aldehyde while chlorophyl a has a methyl group. Therefore, chlorophyl b is more polar.
Spinach Lab Define chromatography and name the four types Define the mobile phase The sample is carried by the mobile phase through the ________ phase. Which is a solid support that contains an _______. What is the absorbent for the stationary phase usually? What is the fancy name for the solvent that is used for the mobile phase called? (can be very polar or less polar) Where is the origin of the sample? Where is the solvent front? What are bands?
Chromatography is a term that refers to techniques for separating, analyzing, and identifying compounds. column, thin layer (TLC), gas (GC), and high performance liquid (HPLC) In each case, a sample mixture is placed in a gas or liquid phase, called the mobile phase. Stationary and absorbent. silica gel or alumina. eluent 1 cm from the bottom Top of where solvent went up the TLC Plate Bands are areas of high concentration.
Acetlyation of Ferrocene Lab For column chromatography, the stationary phase is packed into a glass tube, or _____ which is equipped with a stopcock. The sample is loaded on the top of the column, either as a _________ solution or as a ________ sample absorbed onto a small amount of alumina or silica gel. Is the column eluted by adding solvent from the top or bottom during column chromatography? Will the most polar compounds elute first or the least polar?
Column concentrated solid Top Least polar will elute first.
Acetlyation of Ferrocene Lab When doing column chromatography, what do we need to remember about water? What about the sand? Do we even bother weighing out the silica gel? Once the silica is mixed up in a beaker, we transfer the slurry into the column as ______ as ______. What happens if you allow the volume of the solvent in the column to go below the top of the adsorbent while packing the column? What should the column look like when everything is said and done? Is it ok to reuse the ligroin that drains into the erlenmeyer flask during the column packing? During elution, when do you add more ligroin? How do we add more ligroin back to column?
DO NOT INTRODUCE ANY WATER INTO THE COLUMN! The column will already have a piece of cotton in it, which will support the packing material and prevent it from clogging the stopcock during elution. Make sure the sand is level so that the column elutes properly. Do not weigh silica gel, it is very light and makes a huge mess at the balance. quickly possible Channels form in the packing material that will cause poor separation. Clamp holding column, 1/4 inch of sand, Silica gel, 1/4 inch of sand, cotton, stopcock. Yes reuse that ligroin for elution. You add more ligroin when the muniscus touches the top of the sand above the silica gel. You add ligroin down the side walls of the column so that the ligroin does not disturb the sand.
How do we separate carb acid and a phenol?
Dissolve both in ether extract with bicarb. Use HCl to get carb acid and NaOH + HCl to get phenol.
Acetlyation of Ferrocene Lab What do you do if the TLC analysis showed that unreacted ferrocene was present in the sample?
Elute first with pure ligroin. Elute the ferrocene (yellow). Collect this sample. Repeat process for acetlyferrocene (orange) but with a 70:30 mix of ligroin:ethyl acetate. collect the orange as well Repeat process third time for diacetylferrocene (red) but with pure ethyl acetate. Collect the red as well.
Would you consider ethyl acetate to be a polar or non-polar solvent? Why?
Ethyl acetate is a polar compound because C=O and C-O bonds are polar.
Spinach Lab Non-polar compounds will travel ______ through the stationary phase, and therefore have Rf values closer to _____.
Faster 1
Acetlyation of Ferrocene Lab For EAS reaction mechanisms, what are the two steps? What does Iodine need to be iodonized to an aromatic ring?
First step, the aromatic ring acts as a nucleophile and attacks an electrophile. The aromatic ring is then regenerated through the loss of a proton. Requires the use of an oxidizing agent, such as nitric acid, to oxidize I2 to generate the electrophile.
Acetlyation of Ferrocene Lab What form of acylation did we use in this lab?
Friedel-crafts acylation.
Write a chemical equation for the acid-base reaction that occurs when p-phentidine is dissolved in HCl. Why is HCl used instead of just plain deionized water?
HCl has a higher polarity driving the reaction to the right.
Spinach Lab Why is it important not to dilute the initial sample before it has been loaded onto the chromatography column?
If you dilute the sample prior to loading it on the chromatography column, it can become a wider band. This can cause a problem if you try to separate bands that are already super wide. Broad bands become even more broad upon elution, leading to poor separation of the compounds.
When should you clean up a chemical that you spill in the lab (such as at the balance station)? a) Whenever the TA catches you. b) Immediately. c) At the end of the lab period.
Immediately It is important to clean up any spills right away so that we minimize hazards in the lab. You wouldn't want to work at a messy area, right? How do you know what that white powder or liquidy stuff is that someone left behind? Don't leave messes for others to clean up. Place spilled reagents in the appropriate waste container. Ask your TA if you need help deciding how to clean up a spill or where to dispose of the waste.
Solid-liquid extractions are performed using liquid CO2, as a solvent. Liquid-liquid extractions, the two solvents that are chosen for the extraction must be ________- that is, they must not be soluble in each other. Also, the compound to be extracted must have _________ _________ for the two solvents. After extraction has occured as a water-soluble carboxylate or phenolate ion, neutralization must take place to regenerate the neutral organic compound. Depending on the solubility of the neutral carboxylic acid or phenol in water, the compound may precipitate out of the solution, at which time the precipitate can be isolated by vacuum filtration. If precipitation does not occur, the compound must be extracted from the water using a fresh portion of the organic solvent. This process is often called _____ ______. What is the purpose of brine in an extraction? Anhydrous salt? For an extraction, does the separatory funnel need to be dry?
Immiscible Different affinities Back extractions Brine is used to remove the majority of dissolved water. The anhydrous salt is then used to remove the remaining water. We typically wash the organic layer to get rid of the water using the two solutions above. No it does not need to be dry since it uses aqueous solutions anyways.
How is polymer chemistry different than regular organic chemistry? Lactones are known to undergo _____-_______ transesterification polymerization under acid-catalyzed conditions. These ring opening reactions are examples of ______-_______ type of polymerizations, where an alcohol initiator is used to begin the chain reaction. In this experiment, we used a _____ as the initiator. It is important to note that the initiator contributes very little to the overall characteristics of the resulting polymer since the number of repeating units, n, is quite large relative to a single molecule of initiator.
In polymer chemistry, we use the same kinds of organic reactions but these reactions happen hundreds, maybe thousands, of times to create a polymer. ring-opening chain-growth Diol
Spinach Lab What happens when you increase the ratio of ethyl acetate : hexane in the spinach pigment lab? Remember, we used different ratios for eluent to see which one worked the best.
Increasing the ratio by adding more acetate causes the pigment molecules to travel further up the TLC plate.
4 common routes of chemical exposure
Inhalation Ingestion Injection Absorption
Explain the purpose of the hot gravity filtration. Why is it good to use the stemless funnel for this technique?
It is done to separate insoluble impurities from a hot solution. With a stemmed funnel, the crystals come out as the solution cools, blocking the funnel. Stemless funnel, prevent this form happening.
What is ligroin? Is it polar or nonpolar?
Ligroin is a non-polar solvent and is a flammable liquid.
The homopolymers of d-decalactone and d-dodecalactone are viscous, amorphous liquids with ____ softening temperatures due to the flexibility of the alkyl backbone and side chains. Since the end groups of the homopolymers are _______(what functional group), they can act as initiators for the polymerization of a second monomer, resulting in a linear polymer chain with blocks of two different monomers. What monomer did we use for the second polymerization of this experiment? What is the purpose of adding PLLA homopolymer? The triblock copolymers formed in this experiment are called _______. Note that both lactones have low odor detection limits and persistent aromas, and should be handled IN THE HOOD.
Low alcohol L-lactide It adds strength and rigidity to the material thermoplastics-they can be molded by heating above the melting temperature of the hard poly(l-lactide) blocks.
Making Polymers Lab Polymers are made up of ______. What happens during a condensation polymerization? Classic examples? Would we want to use the diacid chloride or dicarboxylic acid in this experiment? Why? What is the purpose of the NaOH in this polymerization?
Monomers Two monomers react to form a larger unit while a small molecule, like water or HCl, is eliminated or lost. Classic examples would be polyamides and polyesters, nylon-10,6 We want to use diacid chloride since it is more reactive. It neutralizes the HCl releaced each time a new amide bond is formed.
When is it OK to work with chipped or broken glassware in the organic laboratory? a) If it is a small chip or crack. b) If the crack is just a star-crack. c) If the crack seems to be only partway through the glass. d) Never!
NEVER Any crack in a piece of glassware is an accident waiting to happen. Changes in temperature of the glassware during heating or cooling can cause the piece to break, which is a hazard. Replace any chipped, cracked, or broken glassware right away to avoid unnecessary injury.
When performing a recrystallization, we want to have a _____ melting point range. What happens to the melting point range when there are impurities? What do you look for in the solvent for recrystalization? How much solvent do you use? What is the fancy name given to the filtrate?
Never heat any glassware to dryness. Narrow lowers the melting points. Completely dissolve both the desired compound and any other organic impurities when the solvent is HOT (BOTH SOLUBLE). Insoluble in the chosen solvent at cold temperatures, and the organic impurities must remain soluble when the solution is cooled. COLD (COMPOUND INSOLUBLE, IMPURITIES SOLUBLE) The minimum amount of solvent at the boiling point. Mother liquor.
Acetlyation of Ferrocene Lab For the formation of 1,1-diacetylferrocene (red) Two aromatic cyclopentadienyl rings with Fe connecting the two at the center and two acyl groups attached, 1 per ring. Use your knowledge of the mechanism and theory of electrophilic aromatic substitution to explain the formation of this isomer.
Once an acetyl group substitutes on the cyclopentadienyl ring, the ring is deactivated and the other acetyl group must substitute on the other cyclopentadienyl ring that is electron rich.
Spinach Lab The TLC plate should be marked lightly with a ________ approximately ____ cm from the bottom to indicate the starting point which is called the ______.
Pencil 1 cm Origin
Spinach Lab What type of TLC plates are used in organic lab?
Plastic backed TLC plates
Spinach Lab ________ compounds tend to absorb more readily to the stationary phase than ________-___________ compounds. In both column and thin layer chromatography, the solvent that is used for the mobile phase is called the _____.
Polar Non-polar Eluent
Spinach Lab If the component has a greater affinity for the stationary phase, it will travel more _______. If the component has a greater affinity for the mobile phase, it will travel more ______ through stationary phase.
Slowly Quickly
Spinach Lab As the eluent moves up the TLC plate by capillary action, the sample components are carried with it and are separated on the _______ phase.
Stationary
Acetlyation of Ferrocene Lab What do you do with the column at the end of the experiment?
Take column to the TA so he or she can blow the packing material out of the column before you return it to the stockroom. DO NOT WASH WITH WATER!
Should we also expect to receive questions that may have been on the midterm that relate to other experiments? Also, should we expect IR and NMR spectra on the quiz, since they were not tested heavily on the midterm?
The focus will be on the experiments that weren't covered on the midterm. However, the course is cumulative by nature, so important techniques and ideas that we've been using throughout the course would still be fair game on the quiz. The quiz will definitely include spectroscopy since we've been using it throughout the semester.
Spinach Lab Where is the solvent front located? Is it ok for the solvent to evaporate for a few minutes so the plate can dry? What do you do if the TLC does not show colors? What is the range of all Rf values?
The leading edge of the solvent, approximately 1 cm from the TOP of the TLC plate. Yes, the solvent is allowed to evaporate for a few minutes so the plate can dry before it is analyzed. Put the plate under a UV light, which activates the fluorescent indicator on the plates. They can range between 0-1.
Which compound would you expect to elute first from the column: unreacted ferrocene, acetylferrocene, or diacetylferrocene? Why?
The least polar molecule will elute first or unreacted molecule. Meaning ferrocene will go first.
True or False: Light with a higher frequency will have a longer wavelength.
false
Making Polymers Lab Try not to touch the nylon created between the interface of the two layers in the beaker, it is very abrasive to skin at this point. Dry nylon with two pieces of filter paper. What happened when you mixed the monomers left in the reaction mixture vigorously? What was the solubility of the nylon in acetone, toluene, and ethanol?
The nylon bundled up around glass stirring rod. Insoluble in all 3.
Spinach Lab What happens to the pigments after you expose them to air on the TLC plate? Therefore, what do we do?
They oxidize and so we take pictures.
Why do we add warmed ethyl acetate while stirring vigorously with a glass stir rod? What happened after pouring the solution into 40 mL of cold methanol (ice bath)?
To suspend the solid pieces of polymer. The polymer precipitated as a flocculent white powdery material. We then vacuum filtrated the solid and transfered the white polymer material to the aluminum boat which was heated on a hot plate to melt down the polymer and remove the excess solvent.
What does it mean to anneal the copolymer? Will large amount of l-lactide cause a fast or slow anneal?
Use a heat treatment on the copolymer to remove excess solvent. Slow anneal
What is the purpose of the sodium acetate solution in the amide synthesis of acetophenetidin?
Used as a buffer to raise pH. If pH is too low, starting amine will be converted to conjugate acid
Acetlyation of Ferrocene Lab Will there be a problem if the glassware is wet before conducting this experiment? What about after neutralization?
YES keep water away from reaction mixture at anytime prior to neutralization. After neutralization it is fine to use cold water to rinse out the crystals during vacuum filtration. Use filter paper to pat dry the crystals.
5. The solubility of a compound in two solvents is shown in the table below. Based on this information, which is the better solvent choice for recrystallization? Solvent Solubility at boiling point Solubility while in ice bath Solvent A 7.2 g per 100mL 0.22 g per 100mL Solvent B 59 g per 100mL 30 g per 100mL a. Solvent A is better because it has the least solubilty at low temperature b. Solvent B is better because the difference in solubility is the greatest between hot and cold. c. Solvent B is better because the compound is more soluble at hot temperatures. d. Neither solvent A nor B is better, they are both good choices for recrystallization.
a. Solvent A is better because it has the least solubilty at low temperature
It is important that you are properly attired to be safe while working in the lab. Which of the following items are required for admission to the organic teaching lab? a) department approved safety glasses long pants b) shirt (with sleeves) that covers entire upper torso c) flat soled shoes that cover the entire foot d) hair longer than shoulder-length tied back e) all of the above
all of the above Please remember that our goal in this course is to have you learn organic chemistry lab techniques while keeping everyone safe. Wearing proper attire is the first step in preventing injury in case of an accident.
2. If a fire alarm sounds while in the lab, what do you do? a. Gather up all personal belongings, like backpacks and phones b. Unplug all hotplates and leave lab immediately c. If there is no obvious sign of danger, you can ignore the alarm d. All of the above
b. Unplug all hotplates and leave lab immediately
4. An unknown organic compound was analyzed by elemental analysis and found to be 69.7% carbon and 11.7% hydrogen. What makes up the remaining mass of the compound? a) nitrogen b) chlorine c) oxygen d) all of these are possible
c) oxygen
1. Safety in the teaching lab is... a. The responsibility of the instructor only b. The responsibility of the student only c. A shared responsibility of everyone working in the lab
c. A shared responsibility of everyone working in the lab
If I make a mistake in my lab notebook, I should... a) tear out the page and throw it away b) write the correct information on top of the mistake c) scribble out the mistake d)use white-out to cover up the mistake e) draw a single line through the mistake, then enter the correct information
e) draw a single line through the mistake, then enter the correct information Your notebook should be a complete record of EVERYTHING that you did during an experiment, mistakes and all. If you make a mistake, simply draw a line through the error and enter the correct information.
3. You have attempted to recrystallize a reaction product from water, but very few crystals have formed in the mixture. What can you do to improve your recovery? a. Heat the mixture on the hotplate to reduce the volume of the solution slightly. b. Scratch the inner surface of the container with a stirring rod, and place in an ice bath. c. Filter mixture through Büchner funnel to induce crystallization. d. All of the above e. Both (a) and (b) but not (c)
e. Both (a) and (b) but not (c)
Although eating and drinking are not permitted in the organic laboratory, chewing gum and candy are allowed. True False
false This should be obvious - you shouldn't take any risks like this in the lab. Although we try to limit your exposure to hazards as best we can, you will be touching surfaces that may have had chemicals on them, which means that you have transferred that residue to your fingers. Keep your hands away from your face during the lab (no chewing on pens, either!), and be sure to wash your hands when you leave.
It is OK to temporarily remove my safety glasses/goggles while in the laboratory to clean them. True False
false You never know when an accident may happen, and you sure don't want it to be in those few seconds when your eyes aren't protected. Be sure to keep your safety glasses/goggles in place at all times while in the laboratory.
I can wear any type of safety glasses or goggles in the organic lab. True False
false There are many types of safety glasses/goggles on the market, all with various ratings for different applications. We need to be able to identify if your glasses are appropriate for our labs with a quick glance, which is why the Department of Chemistry has chosen a small set of safety glasses/goggles to be used in our courses. Please check the cabinet outside Leigh 238 for examples of approved eye protection.
