Exam 2 Orgo Lab

Ways a primary alkyl bromide (1-Bromobutane) can be prepared in the lab; why the NaBr-H2SO4 method is the preferred method?

-1-butanol is converted to 1-bromobutane by an Sn2 reaction -A primary alkyl bromide can be prepared by heating the corresponding alcohol with: 1. Constant boiling hydrobromic acid (47% HBr) 2. An aqueous solution of sodium bromide and excess sulfuric acid, which is an equilibrium mixture containing hydrobromic acid 3. With a solution of hydrobromic acid produced by bubbling sulfur dioxide into a suspension of bromine in water -Since reagents (2) and (3) contain sulfuric acid at a concentration high enough to dehydrate secondary and tertiary alcohols to undesirable by-products (alkenes and ethers), and hence the HBr method (1) is preferred for preparation of halides of the types R2CHBr and R3CBr Primary alcohols are more resistant to dehydration and can be converted efficiently to the bromides by the more economical methods (2) and (3), unless these are of such high molecular weight that they lack adequate solubility in the aqueous mixtures -The Nabr-H2SO4 method is preferred to the Br2-S)2 method because of the unpleasant choking property of sulfur dioxide

Chromatogram

-A gas chromatogram is simply a recording of current versus time (which is equivalent to a certain volume of helium) -Gas chromatography determines the number of components and their relative amounts in a very small sample

Liquid/Liquid Extraction

-After a chemical reaction has been carried out, the organic product is often separated from inorganic substances by liquid/liquid extractions -The transfer of a solute from one liquid phase to another; most common case is the extraction of an aqueous solution with a suitable organic solvent -EX: synthesis of 1-bromobutane

Reasons for using excess sulfuric acid

-An aqueous solution of sodium bromide and sulfuric acid produce an equilibrium mixture containing the needed hydrobromic acid; in order to shift the equilibrium towards the right with the formation of hydrobromic acid in high yield, sulfuric acid is used in excess -One mole of 1-butanol theoretically requires one mole each of sodium bromide and sulfuric acid, but this procedure calls for the use of a slight excess of bromide and twice the theoretical amount of acid -Excess acid is used to shift the equilibrium in favor of a high concentration of hydrobromic acid

Why is anhydrous CaCl2 the preferred drying agent for this experiment?

-Calcium chloride removes both water and alcohol from a solution -Not as efficient a drying agent as anhydrous sodium sulfate

Peak area

-Different peaks on a chromatogram correspond to different components and the areas under these peaks can be used to quantify the mole fraction of each component. -It tells us the retention time of the small peak (stationary phase) and the retention time of the large peak (mobile phase)

How is distillation used to purify a compound

-Distillation is used to purify a compound by separating it from a non-volatile or less-volatile material -When different compounds in a mixture have different boiling point, they separate into individual components when the mixture is carefully distilled -Compound purification can be performed by: simple and fractional distillation

Butyl methyl ether (MTBE)

-Does not easily form peroxides, so it can be stored for much longer periods than diethyl ether -It is cheaper -Slightly less volatile (bp 55 degrees celsius) so it does not pose the same fire threat as diethyl ether although it is still a flammable substance -The explosion limits for MTBE mixed with air are much narrower than for diethyl ether, the toxicity is less, the solvent power is the same, and the ignition temperature is higher (224 vs. 180 degrees celsius) -MTBE forms an azeotrope with water that boils at 52.6 degrees celsius → this means that evaporation of ant MTBE solution that is saturated with water should leave no water residue unlike diethyl ether

Factors affecting separation in gas chromatography (parameters which we can control to influence the retention time/ separation effectiveness)

-Efficient separation of compounds in GC is dependent on the compounds traveling through the column at different rates -The rate at which a compound travels through a particular GC system depends on the following factors: -Length of the column: the longer the column, the longer it will take all compounds to elute -Longer columns are employed to obtain better separation -Column temperature: raising the column temperature speeds up the passing of all compounds through the column -Flow rate of the carrier gas through the column: increasing the carrier gas flow will increase the speed the compounds move through the column -Column packing polarity: usually, all the compounds will move slower on polar columns, but polar compounds will show a larger effect -Polarity of compounds: polar compounds will move slower, especially if the packing of the column is polar -Volatility of compound: low boiling point compounds (volatile) will travel faster through the column than high boiling compounds

How we purified the product? Role of NaCl saturated sol, role of anhydrous CaCl2

-Extract with ~ 50 ml of saturated NaCl solution to remove the water that might be dissolved in the ether. -To remove the water that might be present in the organic layer -Through the neck of the funnel, transfer the ether (top) layer into an Erlenmeyer and add ~ 5 g CaCl2 pellets (drying agent). Swirl the flask for ~5 min. If needed, repeat using ~2 g CaCl2 -It will "dry" the mixture by eliminating any water that could have been left over from the NaCl step

Concentrated sulfuric acid

-Extremely corrosive -Can cause severe burns -Use great care to avoid contact with skin, eyes, and clothing -Wear gloves and do not touch unprotected skin -Change gloves immediately after handling the acids -In case of accidental contact, wash with copious amounts of water and inform Instructor/TA immediately

Grignard reaction - why is important (formation of C-C bond...)

-Grignard reagents are highly reactive organometallic compounds generated by treating alkyl or aryl halides with magnesium metal in the presence of anhydrous diethyl ether (or other suitable solvent) -They play a significant role in organic synthesis because they react with a large variety of functional groups to form a new carbon-carbon bond therefore allowing the assembly of larger carbon structures from smaller molecules

grignard reagents

-In 1912, Victor Grignard received the Nobel Prize in chemistry for his work on the reaction that bears his name, a carbon-carbon bond-forming reaction by which almost any alcohol may be formed from appropriate alkyl halides and carbonyl compounds -The grignard reagent is easily formed by reaction of an alkyl halide, in particular a bromide, with magnesium metal in anhydrous diethyl ether -The grignard reagent is both a strong base and strong nucleophile -As a base it will react with all protons that are more acidic than those found on alkenes and alkanes -Thus, grignard reagents react readily with water, alcohols, amines, thiols, and so on, to regenerate the alkane -The starting material for preparing the grignard reagent can obtain no acidic protons -The reactants and apparatus must all be completely dry; otherwise the reaction will not start -The magnesium metal, in the form of a coarse powder, has a coat of oxide on the outside -A fresh surface can be exposed by crushing the powder under the absolutely dry ether in the presence of the organic halide -Reaction will begin at exposed surfaces, as evidenced by a slight turbidity in the solution and evolution of bubbles -Once the exothermic reaction starts it proceeds easily, the magnesium dissolves, and a solution of the grignard reagent is formed -The solution is often turbid and gray due to impurities in the magnesium -The reagent is not isolated but reacted immediately with, most often, an appropriate carbonyl compound to give, in another exothermic reaction, the magnesium alkoxide, a salt insoluble in ether -In a simple acid-base reaction this alkoxide is reacted with acidified ice water to give the covalent, ether-soluble alcohol and the ionic water-soluble magnesium salt -In this experiment, we shall carry out another common type of grignard reaction, the formation of a tertiary alcohol from 2 moles of the reagent and one of an ester -The ester employed is the methyl benzoate synthesized -The initially formed product is unstable and decomposes to a ketone, which being more reactive than ester, immediately reacts with more grignard reagent -The primary impurity in the experiment is biphenyl, formed by the reaction of phenylmagnesium bromide with unreacted bromobenzene -The most effective way to lessen this side reaction is to add the bromobenzene slowly to the reaction mixture so it will react with the magnesium and not be present in high concentration to react with previously formed grignard reagent -The impurity is easily eliminated because it is much more soluble in hydrocarbon solvents than triphenylmethanol -Grignard reagents are highly reactive organometallic compounds generated by treating alkyl or aryl halides with magnesium metal in the presence of anhydrous diethyl ether -They play a significant role in organic synthesis because they react with a large variety of functional groups to form a new carbon-carbon bond therefore allowing the assembly of larger carbon structures from smaller molecules -Because of their reactivity, grignard reagents are difficult to preserve and are frequently used "in situ"

Apparatus (separatory funnel); "shake -vent" sequence

-In macroscale experiments, a frequently used method of working up a reaction mixture is to dilute the mixture with water and extract with ether in a separatory funnel -When the stopped funnel is shaken to distribute the components between the immiscible solvents MTBE and water, pressure always develops through volatilization of ether from the heat of the hands, and the liberation of a gas (CO2) can increase the pressure -Consequently, the funnel is grasped so that the stopper is held in place by one hand and the stopcock by the other -After a brief shake or two, the funnel is held in the inverted position and the stopcock opened cautiously to release pressure -The mixture can be shaken more vigorously and pressure released as necessary -When equilibrium is judged to be complete, the slight, constant terminal pressure due to ether is released, the stopper is rinsed with a few drops of ether delivered by a pasteur pipette, and the layer allowed to separate

Mobile phase/carrier gas

-In the lab, the mobile phase, aka the carrier gas, is an inert gas (EX: helium, nitrogen, argon, etc) that continuously flows through the column carrying the sample -The carrier gas, which is a very good thermal conductor -As long as pure helium is flowing over the detector, the temperature of the wire is relatively low and the wire has low resistance to the flow of electric current -Organic molecules have lower thermal conductivities than helium -Hence, when a mixture of helium and an organic sample flows over the detector wire, it is cooled less efficiently and heats up

distillation

-In this experiment, simple distillation was used -Distill the mixture, make frequent readings of the temperature, and distill no more water-insoluble droplets come over, by which time the temperature should have reached 115 degrees celsius -The increasing boiling point is due to azeotropic distillation of n-butyl bromide with water containing increasing amounts of sulfuric acid, which raises the boiling point

Fractional Distillation

-Mixtures of liquids whose boiling points are closer to each other cannot be separated by a single simple distillation → in these situations, a fractional distillation is used -On its way up from the fractionating column, the vapor condenses and is re-vaporized many times -At each stage of condensation/ re-vaporization, the vapor is further enriched in the lower boiling point component -The only difference between the apparatus used for simple distillation and the one used for fractional distillation is the presence of fractionating column

Acid/Base Extraction

-One of the compounds in the mixture is altered chemically to change its solubility characteristics -Generally the compound is altered by making the mixture either acidic or basic -This causes certain classes of organic compounds to form salts that are soluble in water and can be separated in the "aqueous" phase during liquid-liquid extraction -Involves carrying out simple acid/base reactions in order to separate strong organic acids, weak organic acids, neutral organic acids, and basic organic substances

Preparation of alkene isomers from 2-methyl-2- butanol: techniques used to complete the experiment

-Reaction starts in the 100 ml RB flask: the tertiary alcohol, 2-methyl-2-butanol, is mixed with the sulfuric acid to form isomer alkenes: 2-methyl-1-butene (BP = 31.20C) and 2-methyl-2-butene (BP = 38.60C). In order to drive the equilibrium to the right and bring the reaction to completion, the product is removed via fractional distillation. -In this experiment a tertiary alcohol is dehydrated to a mixture of alkenes in a reaction catalyzed by sulfuric acid -The products are collected by simple distillation into an ice-cold test tube -Cold aqueous base is added to remove acid and the organic layer dried with calcium chloride -The products are again distilled and then analyzed by gas chromatography

Molecular sieves

-Sodium alumino-silicates )zeolites) that have well defined pore sizes -The 4A size absorbs water to the exclusion of almost all organic substances and is a fast and effective drying agent but like, Drierite, it is impossible to ascertain by appearance whether enough has been used -Molecular sieves in the form of 1/16in pellets are often used to dry solvents by simply adding them to the container

drierite

-Specially prepared form of calcium sulfate, is a fast and effective drying agent -Difficult to ascertain whether enough has been used -An indicating type of drierite is impregnated with cobalt chloride, which turns from blue to red when it is saturated with water -This works well when gases are being dried, but should not be used for liquid extractions because the cobalt chloride dissolves in many protic solvents

Overall reaction for preparation of 1-Bromobutane from 1-Butanol and NaBr-H2SO4; by what type of reaction/mechanism is the 1-Butanol converted to 1-Bromobutane?

-The Sn2 reaction for converting 1-butanol to 1-bromobutane (n-butyl bromide) is a preparative experiment -This organic synthesis involves a typical preparation and purification of a liquid organic product -Confirmation of the product, 1-bromobutane, will be performed by reacting the product with a solution of sodium iodide in acetone -The 1-bromobutane, a primary alkyl halide, will react with the sodium iodide via an Sn2 mechanism forming an insoluble precipitate

Boiling point determination

-The boiling point is one of the physical properties of a compound by which it can be identified → can be identified using the distillation technique -The boiling point is the temperature at which the vapor pressure of the liquid phase of a compound equals the external pressure (usually the atmospheric pressure) acting on the surface of the liquid -For instance, consider a liquid heated in an open flask -The vapor pressure of the liquid will increase as the temperature of the liquid increases; when the vapor pressure equals the atmospheric pressure, the liquid will boil -Each pure organic solvent has its characteristic boiling point (range) at a certain pressure Compounds with higher vapor pressures will boil at lower temperatures

Distillation column: packing material

-The column is packed with some material on which heat exchange between ascending vapor and descending liquid can take place -A large surface area for this packing is desirable, but the packing cannot be so dense that the pressure changes take place with the column causing nonequilibrium conditions -Also if the column packing has a very large surface area, it will adsorb (hold up) much of the material being distilled -Number of different packings for distillation columns have been tried: glass beads, glass helices, carborundum chips, etc -Best packing = copper or steel sponge (Chore Boy) since it is easy to put into the column, doesn't come out of the column as beads do, and has a large surface area, good heat transfer characteristics, and low holdup

Detector type

-The detector wire actually is one leg of a Wheatstone bridge connected to a chart recorder that records, as a peak, the amount of current necessary to again balance the bridge -The information produced by the recorder is a chromatogram -A gas chromatogram is simply a recording of current versus time (which is equivalent to a certain volume of helium)

Simple Distillation

-The flask should be no more than ⅔ full at the start -Great care should be taken not to distill to dryness because, in some cases, high-boiling explosive peroxides can become concentrated -The liquid is relatively pure to begin with (EX: no more than 10% liquid contaminants) -The liquid has a non-volatile component, for example, a solid contaminant -The liquid is contaminated by another liquid and their boiling points are at least 70 degrees celsius apart -During a simple distillation, the liquid is vaporized and condensed one time

Pressure-build up

-The heat of the hand or heat from acid/base reactions will cause pressure buildup in an extraction mixture that contains a very volatile solvent such as dichloromethane -The extraction container must be opened carefully to vent this pressure -Sodium bicarbonate solution is often used to neutralize acids when carrying out acid/base extractions -The result is the formation of carbon dioxide, which can cause foaming and high pressure build-up -Whenever bicarbonate is used, add it very gradually with thorough mixing and frequent venting of the extraction device -If a large amount of acid is to be neutralized with bicarbonate, the process should be carried out in a beaker

How did we prepare the Grignard reagent (Phenylmagnesium bromide) in the lab (chemical Rx from Williamson p.392 Exp.1); what steps were taken to help start the Rx ; once started, how was the Rx (autocatalytic, exothermic...) and what we have done to keep it under control? Role of the anhydrous ethyl ether in the Rx? Role of Iodine crystal? Why must the apparatus and reagents be completely dry

-The object of this lab is the grignard reaction of a freshly prepared grignard reagent (phenylmagnesium bromide) with an ester (methyl benzoate) to obtain a tertiary alcohol (triphenylmethanol) -Formation of the grignard reagent from a halide and metallic magnesium requires high activation energy (it is difficult to start but once it has started, is autocatalytic and exothermic). -The reaction occurs on the surface of the magnesium turnings, and is formally an oxidation of the metal -The reaction is carried out in anhydrous (dry) ether, diethyl ether solvent; the ether is functioning as a lewis base by solvating the grignard reagent and allowing it to diffuse away from the metal -To help start the reaction: -Minimize the exposure of Mg turnings and the content of the RB flask to air and moisture since it will produce unwanted side reactions -Warm up (use warm water bath) the RB flask to help start Rx -Add the Bromobenzene/Ether mixture at an optimum rate (try 1 - 2 drops/sec) → if bromobenzene is overheated it will produce biphenyl an unwanted purity -Note Signs of reaction starting: bubbles on the surface of Mg, auto-reflux, etc. If Rx does not start, stop adding the Bromobenzene (Why?) and ask for assistance -Once Rx started: If boiling becomes too vigorous briefly touch the RB with the cold water bath; do NOT let the Rx stop -If auto reflux diminishes substantially add few drops of Bromobenzene at a faster rate -Once you have enough liquid in the RB flask, start the magnetic stirring (on low at first, then increase as needed) -Gentle boiling and auto-reflux should be maintained throughout the addition of Bromobenzene

"Drying" an organic liquid

-The organic solvents used for extraction dissolve not only the compound being extracted but also water -Evaporation of the solvent then leaves the desired compound contaminated with water -If ether that contains dissolved water is shaken with a saturated aqueous solution of sodium chloride, water will be transferred from the MTBE to the aqueous layer -Solvents like dichloromethane do not dissolve as nearly as much water and therefore are dried over a chemical drying agent (CaCl2) -To choose a chemical drying agent: -The possibility of reaction with the substance being extracted -The speed with which it removed water from the solvent -The efficiency of the process -The ease of recovery from the drying agent -Some very good but specialized and reactive drying agents potassium hydroxide, anhydrous potassium carbonate, sodium metal, calcium hydride, lithium aluminum hydride, and phosphorous pentoxide -Substances that are essentially neutral and unreactive and are widely used as drying agents include anhydrous calcium sulfate (drierite), magnesium sulfate, molecular sieves, calcium chloride, and sodium sulfate

Solid/Liquid extraction

-The removal of a substance of interest from a natural product or a solid mixture using a suitable solvent -EX: coffee or tea making; hot water is used to extract caffeine from coffee beans or tea leaves

Product characterization: significance of MP range; % yield calculation, reasons for low yield

-The significance of melting point range is to help determine if our experimental product is similar to the actual product by comparing the melting point range -If our experimental product had a lower or higher melting point range compared to the actual value, there is a chance that there is an impurity within our final produce -% yield calculation tells us how much of our product did we obtain compared to the theoretical value that was already determined -Reasons for low yield: there could have been side reactions from: -Large rate of bromobenzene excess when adding to Mg turnings, causing overheating and making impurity biphenyl -Could have reacted with oxygen in the air if the reflux wasn't strong or present in the reaction -Not all the glassware could have been cleaned or completely dry allowing it to react with water -When using the separatory funnel, may have not taken out the bottom (impurity) layer all the way causing some impurities to stick around during recrystallization -May have needed to add more CaCl2 drying agent if solution shows clumped pellets of CaCl2 -The crystals may have not been completely dry causing an impurity when doing the melting point

GC column types

-The stationary phase is coated inside a GC column (capillary column or packed column) and greatly influences the separation of the compounds -Nowadays most columns used in GC are capillary columns -A typical capillary column is 15 to 60 m long and has an interior diameter (ID) of 0.25 to 0.32 mm -A packed column is usually shorter, 2 to 4 m, and has a larger (~2mm) ID -The GC stationary phase consists of large molecular weight, high boiling point liquids coasted on diatomaceous earth (polysiloxane, polyethylene glycol, or polyester polymers)

Why we used hexanes in the recrystallization?

-They are the ideal solvent because they dissolve the entire solute when heated but not when cold 1. They completely dissolve the solute when hot (the solvent), but not dissolve when cold -Either not dissolve the impurities at all or dissolve them very well -Not react (chemically) with the solute -It is volatile

Extraction

-Used in order to purify the crude 1-bromobutane -Purification of crude 1-Bromobutane using extraction with: -Distilled water (in the conical tube): top layer- aqueous (discard into "waste" beaker)/ bottom layer - organic (keep) -Saturated sodium bicarbonate solution (in the conical tube): top layer- aqueous (discard into "waste" beaker)/ bottom layer - organic (keep) -Saturated sodium bicarbonate solution (in the separatory funnel): collect bottom layer - organic (1-Bromobutane) into a clean and dry Erlenmeyer flask -Dry the product with anhydrous CaCl2

Calcium chloride

-Very fast and effective drying agent -Has the advantage that is clumps together when excess water is present so that it is possible to know how much to ass by observing its behavior -Some calcium chloride reacts with some alcohols, phenols, amides, and some carbonyl-containing compounds -Advantage is sometimes taken of this property to remove not only water from a solvent but also for example, a contaminating alcohol -Since MTBE forms an azeotrope with water its solutions should, theoretically not need to be dried; evaporation carried away the water -Drying these ether solutions with CaCl2 pellets removes water droplets that get carried into the ether solution

Sodium sulfate

-Very poor drying agent -Has high capacity for water but is slow and not very efficient in the removal of water -The pellets clump together when wet -Should still be used for compounds that react with calcium chloride

How did we confirm the product is indeed 1-Bromobutane?

-We confirmed that our product was 1-bromobutane by using the sodium iodide test for primary alkyl halides -Organic halides that can react by an Sn2 mechanism give a precipitate of NaX with sodium iodide in acetone -In our experiment, the presence of a precipitate indicates the tested compound is 1-bromobutane, a primary halide -We would compare our product from lab by adding NaI to a vial and shaking it to see if it forms a precipitate like pure 1-bromobutane with NaI

Stationary phase

-Widely used stationary phases are silicone oil and silicone rubber, both of which can be used at temperatures up to 300 degrees celsius and separate mixtures on the basis of boiling point differences of the mixture's components -More specialized stationary phases will, for instance, allow alkanes to pass through readily (short retention time) while holding back (long retention time) alcohols by hydrogen bonding to the liquid phase

emulsions

-is a suspension of one liquid as droplets in another -Detergents stabilize emulsions, and so anytime a detergent like molecule happens to be in the material being extracted there is the danger that emulsions will form EX: caffeine from tea -Once formed emulsions can be quite stable -Prevention is the best cure for emulsions -Shaking the solution to be extracted very gently until you see that the two layers will separate readily -If a bit of emulsion forms it may break simply on standing for a sufficient length of time -Making the aqueous layer highly ionic will help -Add as much sodium chloride as will dissolve and shake the mixture gently -Vacuum filtration sometimes works and , when the organic layer is the lower layer, filtration through silicone-impregnated filter paper is an aid -Centrifugation works very well for breaking emulsions

Partition coefficient

-is an equilibrium constant with a certain value for a given substance, pair of solvents, and temperature -To a good approximation the concentration of the solute in each solvent can be correlated with the solubility of the solute in the pure solvent -The ratio of the solubility (g solute/100 ml solvent or g solute/ml solvent) of a solute in two immiscible solvents at a certain temperature: k= solubility of solute in the extraction solvent / solubility of solute in the original solvent -The concentration of the solute in each solvent, at a certain temperature, can be correlated with its solubility of the two solvents: K = concentration of solute in the extraction solvent/ concentration of solute in the original solvent -used to evaluate the effectiveness of an extraction by calculating the amount of solute in each layer following an extraction process

reflux

-is the process of boiling reactants while continually cooling the vapor and returning it back to the flask as a liquid -It is used to heat a mixture for longer time at certain temperature without evaporation of the compounds of the mixture -The reflux apparatus consists of a water-cooled condenser attached to the RB flask -Always use a couple boiling chips to keep the boiling solution from 'bumping' -If the heating rate has been correctly adjusted, the liquid being heated under reflux will travel only partly up the condenser tube before condensing -Below the condensation point, solvent will be seen running back into the flask; above it, the condenser will appear dry -The boundary is marked by a "reflux ring" In heating under reflux, the rate of heating should be adjusted so that the reflux ring is no higher than a third to a half of the distance to the top of the condenser

Retention time (tr)

-is the time is takes a solute to travel through the column (the time required for the compound to elute off the column) -The retention time is assigned to the corresponding solute peak and is a measure of the amount of time a solute spends in a column (it is the sum of the time spent in the stationary phase and the mobile phase)

Diethyl ether

-is usually referred to simply as ether, is probably the most common solvent used for extraction, but -it is highly flammable -It has high solvent power for hydrocarbons and for oxygen containing compounds -It is highly volatile (bp 34.6 degrees celsius) and therefore easily removed from an extract -Disadvantages: it is highly flammable and so poses a great fire threat and it easily forms peroxides -The reaction of diethyl ether with air is catalyzed by light -The resulting peroxides are higher boiling than the ether and are left as a residue when the ether evaporates -If the residue is heated, it will explode because ether peroxides are treacherous high explosives

suitable extraction solvent

-should readily dissolve the substance to be extracted -Should not react chemically with the substance to be extracted -Should not react with or be miscible with the other solvent (many times the second solvent is water or an aqueous solution) -Should have a low boiling point so it can be easily removed from the product -Should not be flammable or have high toxicity -Should be relatively inexpensive

Preparation of alkene isomers from 2-methyl-2- butanol: reasons for the ratio of 2-methyl-1-butene to 2-methyl-2-butene

-the mechanism of this reaction involves the intermediate formation of the relatively stable tertiary carbocation followed by loss of a protein either from a primary carbon atom to give the terminal olefin, 2-methyl-1-butene, or from a secondary carbon to give 2-methyl-2-butene -Each step of this e1 elimination reaction is reversible, and thus the reaction is driven to completion by removing one of the products, the alkene → in these reactions several alkenes can be produced -The saytzeff rule states that the more substituted alkene is the more stable and thus the one formed in larger amount → and the trans-isomer is more stable than the cis-isomer

Distillation

-the process of heating the solution to boiling and condensing the vapors above the boiling liquid -EX: cyclohexane and toluene -When the vapor pressure of the liquid equals the applied pressure the liquid boils, it will show that at 760 mm pressure, standard atmospheric pressure, both of these liquids boil at about 78 degrees celsius and 111 degrees celsius respectively -If one of these pure liquids were to be distilled, we would find that the boiling point of the liquid would equal the temperature of the vapor and that the temperature of the vapor would remain constant throughout the distillation

Magnesium sulfate

Fast and fairly effective drying agent, but it is so finely powdered that is always requires careful filtration for removal

What substance is the white precipitate that forms when the 1-Bromobutane reacts with the NaI solution in acetone (see reaction below): NaI + CH3CH2CH2CH2Br CH3CH2CH2CH2I + NaBr (colorless liquid) (white pp.)

The substance that forms a white precipitate is sodium bromide

Extraction efficiency: single vs. multiple extractions

Theoretically it is more efficient to extract the solute multiple times with smaller volumes of solvent than one time with a larger volume of solvent (refer to pg. 105 for mathematical example) Obviously there is a point at which the increased amount of A extracted does not repay the effort of multiple extraction, but keep in mind that several small-scale extractions are more effective than one large-scale extraction