Review Experiments Formation of Polymers Reduction of Vanillin

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1 Review Experiments Formation of Polymers What is a polymer? What is polymerization? What is the difference between an addition polymerization and a condensation polymerization? Which type of polymerization was used to form styrene? The epoxy resin? What determines the physical properties of a polymer? What is thermosetting? In the polymerization to form BADGE, two phenols are deprotonated using NaOH and this intermediate is reacted with epichlorohydrin. What type of mechanism is the addition to epichlorohydrin? When the BADGE polymer was initially formed, what physical quality did you note? When is cooled, what was the BADGE polymer like? When the formation of polystyrene was started, the styrene was treated with a basic solution of NaOH, followed by a water wash, drying with calcium chloride pellets and then the styrene was put through a short pipette chromatography column. What needed to be removed first from the styrene before the polymerization could occur? What gas was given off during the initial heating of the styrene? Where did it come from? Describe the quality of the polystyrene prior to washing with methanol. And after the methanol washes? Reduction of Vanillin Why is sodium borohydride preferred over lithium aluminum hydride for the reduction of an aldehyde to an alcohol? There s a safety reason and a practical reason. Vanillin is mostly insoluble in water but soluble in aqueous sodium hydroxide solution? What did you add to make the vanillin dissolve and explain why it dissolves. What four purposes did aqueous hydrochloric acid serve in the reduction of vanillin to vanillyl alcohol? What is the mole ratio of hydride per mole of sodium borohydride? How many moles of aldehyde are reduced by one mole of sodium borohydride? Bubbles of gas were seen given off during the reduction of vanillin using sodium borohydride in sodium hydroxide solution? What gas was that? Why did it form? Boric acid, H 3 BO 3 is formed as a by-product in this reduction reaction. How is it removed from the product? Why does the addition of HCl cause the formation of crystals of product? What reaction is occurring and why doesn t the product stay dissolved in the aqueous solution?

2 Why did the ph of the aqueous solution have to be 1? If it wasn t ph = 1, how would that lower the yield of vanillyl alcohol? Oxidation of Cyclohexene to Adipic Acid Industrial preparation of adipic acid is usually done using potassium permanganate. Besides being a harsh oxidizer, what problem is associated with the use of potassium permanganate? Nitric acid is also used in oxidation reactions. What two problems exist with the use of nitric acid as an oxidizing agent? Why is a phase-transfer catalyst required for this reaction? What is the by-product for this tungstate and hydrogen peroxide oxidation? How is a phase transfer catalyst able to exist in both aqueous solutions AND organic solvents? Neither Aliquat 336 nor sodium tungstate are going to be the limiting reagent for this reaction. Why not? The hydrogen peroxide also is not the limiting reagent in this reaction. Why not? How will the cyclohexene be weighed out on the balance? Explain why the phase transfer catalyst is called a catalyst (besides lowering the activation barrier). Explain how the sodium tungstate is used catalytically. Explain the sequence of steps that must occur in order for it to oxidize the cyclohexene, over and over again, in this reaction. List ways in which this experiment is green, besides using water as a solvent or generating water as a by-product (No bad by-products). The starting material is being recycled from an old lab and the aqueous solution can be recycled for another reaction. Reagents are used catalytically so less chemicals are being used. Formation of Benzoic Acid Why is diethyl ether considered an inert solvent? What does inert mean? What else does diethyl ether do that is helpful in this reaction? What reagent did we use to form the carboxyl group on the aromatic ring? Explain why the Grignard reagent attacks the carbonyl carbon atom. Why cannot acidic protons be present when doing a Grignard reaction? Or to rephrase: Why must all the glassware be well dried before attempting a Grignard reaction? What does the word anhydrous mean? How did we make the reaction as anhydrous as possible? What was the purpose of the drying tube? What did it dry? There are two by-products formed in this process. List them and why they might form in this process. Write their equations for formation.

3 The ether solution may contain a third organic compound, besides the two mentioned in the previous question. What third compound may also be present? How do you use TLC to identify compounds in the ether layer? If your TLC of your ether layer showed the presence of benzoic acid, what step in the work-up process did you not do well? When the aqueous HCl solution is added to the bromomagnesium salt of benzoic acid, what reaction occurs? Is the organic product of this acidification soluble in the ether layer or the aqueous layer? All of the following are present after the FIRST addition of aqueous HCl: benzoic acid, unreacted bromobenzene, benzene, biphenyl, and inorganic salts. What is contained in the ether layer and what is contained in the aqueous layer? When aqueous sodium hydroxide is added to the ether layer, what reaction occurs? Why is the aqueous sodium hydroxide added? Why did you do three washes/extractions with sodium hydroxide? Why was the sodium hydroxide layer heated gently? How were colored impurities removed? How was the final benzoic acid product isolated from the aqueous solution? If you fail to completely acidify, you won t get complete precipitation of product. Why? Is benzoic acid polar or non-polar? Is the salt of benzoic acid polar or non-polar? Formation of Lidocaine Part 1 Why does reaction occur at the carbonyl carbon and not the carbon attached to the chloride (2 reasons)? Explain why the carbonyl carbon is more REACTIVE from an electronic stand-point and why its less sterically hindered? Why does this reaction have to occur under anhydrous conditions (i.e. glacial acetic acid, the solvent, is anhydrous)? What side reaction will occur that would result in the formation of a by-product that would mean less actual desired product forming? What reaction occurs between acetic acid and 2,6-dimethylaniline? What reaction occurs between HCl and 2,6-dimethylaniline? Which reaction from the two listed directly above is considered a bad reaction and why? Why is sodium acetate added? What is it removing? What two purposes does the aqueous solution of sodium acetate serve? What causes the product to precipitate from the solution? Is the product polar or non-polar? What is removed by the cold water washes of the product from the first step of the lidocaine sequence? Formation of Lidocaine Part 2 What kind of mechanism is this second step for the formation of lidocaine.

4 What three purposes does the diethylamine serve in this reaction? What would be the problem if only one equivalent of diethylamine were used? Why will the nucleophile not attack the carbonyl of the α-chloro-2,6- dimethylacetanilide reactant? What salt is formed during the reaction? How is the excess solvent, diethylamine, removed after the reaction is complete? What purpose does the aqueous solution of hydrochloric acid serve? What is removed in the Hirsch funnel if the acidification is done correctly but a solid appears that won t dissolve. What is that solid? What is added to make lidocaine insoluble from the aqueous acid solution? What is used to extract the lidocaine from the aqueous solution? What would be the ramifications for your yield of not completely basifying the solution (ph = 14)? Why is that? Why is the product soluble in petroleum ether and not aqueous base? What drying agent is used in this reaction? What s the purpose of a drying agent? Esterification to form Isobutyl Propionate What is the driving force for the formation of isobutyl propionate from propionyl chloride and isobutyl alcohol? Why is no acid catalyst required? Why must this reaction also occur under anhydrous conditions? What side reaction might occur if water were present during the reaction? What purpose(s) does water serve during the purification of isobutyl propionate? Why is the product layer washed with aqueous sodium hydroxide solution? What drying agent is used to remove water from the product? How did you know when the product was dry? What equipment could be used for the final purification of the ester product? What problems can occur with the use of this piece of glassware? (You should be able to name and identify the purposes to ALL of the glassware in your kit at this point.) How was HCl gas removed during the reaction? During the work-up? Why isn t the product soluble in the aqueous solutions used to wash the product? The product also has no major reactivity for aqueous acid or aqueous base solutions. Its very difficult to turn it into a salt to get it to dissolve in any aqueous solution. Compare that to the amine in lidocaine and the phenol in vanillin and the carboxylic acid in benzoic acid. What was needed to make the amine soluble in an aqueous solution? And the phenol? Aldol Condensation Why was the reaction in the lab referred to as a mixed Aldol?

5 The choice of aldehyde/ketone is important when using different carbonyl compounds in an Aldol condensation. Why is the use of benzaldehyde/panisaldehyde helpful in getting a single product when reacting with a ketone, like acetone? What does catalytic in base mean for a reaction and its mole ratios? What determines if the reaction you did in lab occurs as a single condensation or a double condensation reaction? What is the driving force for an Aldol condensation? The aldehyde was insoluble in the basic solution. Why? What did the water washes remove from the crude Aldol product? Why was the vacuum repeatedly turned off, and then back on, during the filtration process? Why is HOT solvent required for the recrystallization process? OR What problem will occur if you use barely warm solvent during your recrystallization? Why should you NOT remove the Erlenmeyer flask from the hot water bath before your crystals are completely dissolved? What problem occurs if you do not completely cool your crystals prior to vacuum filtration? Friedel-Crafts Alkylation Why was it unnecessary to measure the exact amount of the aluminum chloride used? Why shouldn t you take the time to carefully measure the aluminum chloride? It is generally accepted that the catalyst forms an activated electrophile in the form of a carbocation intermediate from the alkyl halide. Why is this probably not the case when using 1-bromopropane? What is the significant problem for the Friedel-Crafts alkylation reaction when using a primary alkyl halide? It is generally accepted that the catalyst forms an activated electrophile in the form of a carbocation intermediate from the alkyl halide. Why is this probably not the case when using 1-bromopropane? What two products form in the alkylation of para-xylene, with aluminum chloride and 1-bromopropane? How do the cold temperatures used by the front bench students encourage the formation of a n-propyl substitution product? How do the hot temperatures/order of addition used by the back bench students encourage the formation of an isopropyl substitution product? Show the mechanism of rearrangement of the primary system to the secondary carbocation. Recall that this hydride shift requires heat in order to occur (activation barrier must be overcome). Why didn t the center bench students have as good of results as the back bench students?

6 You should be familiar with all techniques used during this semester s laboratory experiments, including but not limited to vacuum filtration, gravity filtration, reflux, distillation, melting points, drying processes, decolorizing processes, ph analysis. All calculations, including calculation of millimoles of reagents using molecular formulas and/or density values, determination of limiting reagent, theoretical yield (grams) and percent yield are all fair game as well.