Question: Propose a mechanism for the acid-catalyzed

> Methionine enkephalin is a pentapeptide that is produced by the body to control pain. From the sequence of its amino acid residues, draw a bondline structure of methionine enkephalin. N terminus C terminus Tyr-Gly-Gly-Phe-Met Methionine enkephalin

> Draw a bond-line structure of the peptide that corresponds with the following sequence of amino acid residues and identify the N terminus and C terminus: Trp-Val-Ser-Met-Gly-Glu

> Draw the predominant form of Asp-Lys-Phe at physiological pH.

> Using three-letter abbreviations, identify all possible acyclic tripeptides containing L-leucine, L-methionine, and L-valine.

> Using an asymmetric catalytic hydrogenation, identify the starting alkene that you would use to make L-histidine.

> How many different pentapeptides can be constructed from the 20 naturally occurring amino acids in Table 25.1? From Table 25.1: TABLE 25.1 THE STRUCTURES OF THE TWENTY NATURALLY OCCURRING AMINO ACIDS THAT ARE FOUND IN PROTEINS Name Structure Abbrev

> Show how racemic valine can be prepared by each of the following methods: a. The Hell–Volhard–Zelinsky reaction b. The amidomalonate synthesis c. The Strecker synthesis

> Predict the major product(s) in each of the following cases: ? он 1) Rrz. PRI, 2) H,0 3) Excess NH3 (a) ? 1) NICI, NaCN 2) H,0 (b) EIO OEt 1) NANF 2) CH,I 3) H,0", heat ? N. (c)

> The amidomalonate synthesis can be used to prepare amino acids from alkyl halides. When the amidomalonate synthesis is used to make glycine, no alkyl halide is required. Explain.

> The following compound was isolated from nerve cells: a. Describe how this compound differs in structure from fats and oils. b. Three products are obtained when this compound is hydrolyzed with aqueous sodium hydroxide. Draw the structures of all three

> Acrolein is an α,β-unsaturated aldehyde that is used in the production of a variety of polymers. Acrolein can be prepared by treating glycerol with an acid catalyst. Propose a plausible mechanism for this transformation. OH

> Starting with the following compound and using any other reagents of your choice, outline a synthesis for trimyristin: エ

> Limonene is an optically active compound isolated from the peels of lemons and oranges. a. Is limonene a monoterpene or a diterpene? b. Treatment of limonene with excess HBr yields a compound with the molecular formula C10H18Br2. Identify the structure

> Identify the reagents you would use to convert oleic acid into each of the following compounds: a. Stearic acid b. Ethyl stearate c. 1-Octadecanol d. Nonanedioic acid e. 2-Bromostearic acid

> Olestra is a noncaloric oil substitute that is produced by esterifying sucrose with eight equivalents of fatty acids obtained from the hydrolysis of vegetable oils. The eight fatty acid residues give Olestra the consistency and flavor of cooking oil, bu

> Identify the products expected when estradiol is treated with each of the following reagents: a. Excess Br2 b. PCC c. A strong base followed by excess ethyl iodide d. Excess acetyl chloride in the presence of pyridine

> Using vinyl acetate as your only source of carbon atoms, design a synthesis for the following polymer: OAc Vinyl acetate

> When ethylene oxide is treated with a strong nucleophile, the epoxide ring is opened to form an alkoxide ion that can function as a nucleophile to attack another molecule of ethylene oxide. This process repeats itself, and a polymer is formed. The resul

> When 3-methyl-1-butene is treated with a catalytic amount of BF3 and H2O, a cationic polymerization process occurs, but the expected homopolymer is not formed. Instead, a random copolymer is obtained. a. Explain why there are two different repeating uni

> Draw the enantiomer of cholesterol.

> For a pair of keto-enol tautomers, explain how IR spectroscopy might be used to identify whether the equilibrium favors the ketone or the enol.

> Draw the structure of an achiral triglyceride that contains two oleic acid residues and one palmitic acid residue.

> When a solution of aqueous sodium hydroxide is spilled on polyester clothing, a hole develops in the fabric. Describe how the polyester is destroyed.

> As described in the Practically Speaking box in Section 27.7, poly(vinyl alcohol) is used as a precursor to make PVB for use in automobile windshields. Poly(vinyl alcohol) can be prepared by polymerizing vinyl acetate and then removing the acetate groups

> Draw the polymer that is expected when the following monomers react under acidic conditions. You may find it helpful to review Section 19.6. NH, ? (H*) H,N

> Consider the structure of the following polymer: a. Draw the monomers you would use to prepare this polymer. b. Determine whether this polymer is a step-growth polymer or a chain-growth polymer. c. Determine whether this polymer is an addition polymer

> Draw segments of the following polymers, indicating the stereochemistry with wedges and/or dashes. a. Syndiotactic poly(vinyl chloride) b Isotactic polystyrene

> Cationic polymerization of para-methoxystyrene occurs much more rapidly than cationic polymerization of meta-methoxystyrene. Explain this difference in rate.

> Cationic polymerization of para-methoxystyrene occurs much more rapidly than cationic polymerization of styrene. Explain this difference in rate.

> Anionic polymerization of para-nitrostyrene occurs much more rapidly than anionic polymerization of styrene. Explain this difference in rate.

> The following monomer can be polymerized under either acidic or basic conditions. Explain. CN OMe

> Propose an efficient synthesis for the following transformation:

> Polyformaldehyde, sold under the trade name Delrin, is a strong polymer used in the manufacture of many guitar picks. It is prepared via the acid-catalyzed polymerization of formaldehyde. a. Draw the structure of polyformaldehyde. b. Would you describe

> Explain why vinyl shower curtains develop cracks over time

> Nitroethylene undergoes anionic polymerization so rapidly that it is difficult to isolate nitroethylene without it polymerizing. Explain

> Determine whether the following pairs of monomers would form chain-growth polymers or step-growth polymers. NO2 Ph -OH (а) НО он (b)

> Draw the condensation polymer produced when 1,4-cyclohexanediol is treated with phosgene.

> Draw the monomer(s) required to make each of the following condensation polymers: (a) (b) エーZ zーエ エーZ

> Quiana is a synthetic polymer that can be used to make fabric that mimics the texture of silk. It can be prepared from the following monomers: a. Draw the structure of Quiana. b. Is Quiana a polyester, a polyamide, a polycarbonate, or a polyurethane?

> Identify the repeating unit of the polymer formed from each of the following reactions and then determine whether the polymer is a chain-growth or a step-growth polymer. NH, CO,H ? [H*] čO,H NH. (a) O=C=N он ? OH (b) HO ? (с) но

> Identify which of the following monomers would be most reactive toward anionic polymerization: OAc CN CH,

> Identify which of the following monomers would be most reactive toward cationic polymerization: OAc

> 88. Which of the following is the least reactive toward Friedel– Crafts conditions? 89. What is the major product of this reaction? 90. Which reaction sequence best accomplishes this transformation? CH, NO2 OCH (a) (b) (c) (d) B

> Draw a region of an alternating copolymer constructed from vinyl chloride and ethylene.

> Draw a region of a block copolymer constructed from isobutylene and styrene.

> Draw the structures of the monomers required to make the following alternating copolymer: un E-0-E エーOーエ ひ-6-5 エーOーエ

> Kodel is a synthetic polyester with the following structure: a. Identify what monomers you would use to make Kodel. b. Would you use acidic conditions or basic conditions for this polymerization process? In Kodel

> Draw and name the polymer that results when each of the following monomers undergoes polymerization: H NO, H CN H C=C C= H H H H (a) Nitroethylene (b) Acrylonitrile (c) Vinylidene fluoride

> Polyethylene is used to make Ziploc bags and folding tables. Identify which of these applications is most likely to be made from HDPE and which is most likely to be made from LDPE.

> Polyisobutylene cannot be described as isotactic, syndiotactic, or atactic. Explain.

> Should this polymer be classified as a chain-growth polymer or a step-growth polymer?

> Would these pairs of monomers form chain-growth or step-growth polymers? H,N- NH2 CN (a) ci CI (b)

> 88. Which of the following is the predominant form of proline at physiological pH (pH = 7.4)? 89. Which of the following terms properly describes this peptide? a. Tripeptide b. Tetrapeptide c. Pentapeptide d. Hexapeptide OH он N. H. (a) (b) N-H

> Nylon 6 is a polyamide used in the manufacture of ropes. It can be prepared via hydrolysis of ε-caprolactam to form ε-aminocaproic acid followed by acid-catalyzed polymerization. a. Draw the structure of Nylon 6. b. Compare th

> Identify the condensation polymer that would be produced when phosgene is treated with 1,4-butanediol.

> Identify the monomers required to make each of the following condensation polymers (a) (b)

> Kevlar is a condensation polymer used in the manufacture of bulletproof vests. Identify the monomers required for the preparation of Kevlar. H N- H N- Kevlar

> Draw the polymer that would be generated from the acidcatalyzed reaction between oxalic acid and resorcinol. HO. OH + HO OH Oxalic acid Resorcinol

> Draw the mechanism of formation of PET in acidic conditions. It might be helpful to first review the mechanism for the Fischer esterification process.

> A tube of superglue will harden if it remains open too long in a humid environment. Draw a mechanism that shows how superglue polymerizes in the presence of atmospheric moisture. When drawing your mechanism, make sure to draw the initiation step, at leas

> Many monomers that readily undergo cationic polymerization, such as isobutylene, will not readily undergo anionic polymerization. Styrene, however, can be effectively polymerized via cationic, anionic, or radical addition. Explain.

> Arrange the following monomers in order of reactivity toward anionic polymerization: NO2

> Arrange the following monomers in order of reactivity toward cationic polymerization: OAc NO2 CH3

> Draw a plausible mechanism for the following transformation: NO, NO, NAOH, H,O Heat

> Determine whether preparation of each of the following polymers would best be achieved via cationic addition or anionic addition: CN CN CN CN OMe OMe OMe OMe (a) (b) OAc (c) OAc OAc OAc NO2 NO2 NO2 NO2 Cla CCl, Cla ÇCla (d) (e) (f)

> Identify the monomers required to make the following alternating copolymer: ÇH3 H C-C-C-C- CH, H E-0-I エーQーエ I-0-I

> Draw a region of a block copolymer constructed from propylene and vinyl chloride.

> Draw a region of an alternating copolymer constructed from styrene and ethylene.

> Sodium polyacrylate is a synthetic polymer used in diapers, because of its ability to absorb several hundred times its own mass of water. This extraordinary polymer is made from another polymer, poly(methyl acrylate), via hydrolysis of the ester groups.

> Draw and name the polymer that results when each of the following monomers undergoes polymerization: OAc Br CH,CH, C=C H C=C C=C H H H H (a) Vinyl acetate (b) Vinyl bromide (c) a-Butylene

> Treatment of cholesterol with a peroxy acid (RCO3H) could potentially produce two diastereomeric epoxides. a. Draw both diastereomeric epoxides. b. Only one of these epoxides is formed. Predict which one and explain why the other is not formed.

> Sphingomyelins are lipids with the following general structure: a. Identify the polar head and all hydrophobic tails in sphingomyelins. b. Do sphingomyelins have the appropriate structural features and three-dimensional geometry necessary to be major c

> Circle the isoprene units in each of the following compounds: (a) Bisabolene (b) ) Flexibilene HO (c) Humulene (d) Vitamin A OH (e) Geraniol (f) Sabinene

> Draw a mechanism for the base-catalyzed transesterification of trimyristin using ethanol in the presence of sodium hydroxide.

> 87. What is the major product of this reaction? 88. Which compounds will react with each other in the presence of catalytic acid to give CH3CH2CO2C(CH3)3 via a Fischer esterification process? 89. Which of the following structures is not an intermediat

> Draw a mechanism for the transesterification of trimyristin using excess isopropanol in the presence of an acid catalyst.

> Draw the structures of trimyristin and tripalmitin and determine which is expected to have the lower melting point. Explain your choice.

> One of the compounds present in carnauba wax was isolated, purified, and then treated with aqueous sodium hydroxide to yield an alcohol with 30 carbon atoms and a carboxylate ion with 20 carbon atoms. Draw the likely structure of the compound.

> Identify which of the following statements applies to tristearin: a. It is a solid at room temperature. b. It is unreactive toward molecular hydrogen in the presence of Ni. c. It undergoes hydrolysis to produce unsaturated fatty acids. d. It is a com

> Which of the following statements applies to triolein? a. It is a solid at room temperature. b. It is unreactive toward molecular hydrogen in the presence of Ni. c. It undergoes hydrolysis to produce unsaturated fatty acids. d. It is a complex lipid.

> Which of the fatty acids in the previous problem has four carbon-carbon double bonds?

> Identify each of the following fatty acids as saturated or unsaturated: a. Palmitic acid b. Myristic acid c. Oleic acid d. Lauric acid e. Linoleic acid f. Arachidonic acid

> Identify whether hexane or water would be more appropriate for extracting terpenes from plant tissues. Explain your choice.

> Arrange the following compounds in order of increasing water solubility: a. A triglyceride constructed from one equivalent of glycerol and three equivalents of myristic acid b. A diglyceride constructed from one equivalent of glycerol and two equivalen

> Tristearin is less susceptible to becoming rancid than triolein. Explain.

> Identify what reagents you would use to make the following compound with a Robinson annulation reaction:

> Predict the major product for each of the following transformations: OH ? 1) Brg, PBr3 2) H,0 ? 1) Brz, PBr3 (а) 2) H,0 (b)

> Draw the structure of trans-oleic acid.

> Which of the following compounds are lipids? a. L-Threonine b. 1-Octanol c. Lycopene d. Trimyristin e. Palmitic acid f. d-Glucose g. Testosterone h. d-Mannose

> Draw a chiral triglyceride that contains one palmitic acid residue and two myristic acid residues. Will this compound react with molecular hydrogen in the presence of a catalyst?

> Draw two different cephalins that contain one lauric acid residue and one myristic acid residue. Are both of these compounds chiral?

> Predict the product(s) formed when tripalmitolein is treated with each of the following reagents: a. Excess H2, Ni b. Excess NaOH, H2O

> Identify each of the following compounds as a wax, triglyceride, phospholipid, steroid, prostaglandin, or terpene: a. Stanozolol b. Lycopene c. Tristearin d. Distearoyl lecithin e. PGF2 f. Pentadecyl octadecanoate

> Draw a mechanism for the biosynthesis of α-farnesene starting with dimethylallyl pyrophosphate and isopentenyl pyrophosphate. -Farnesene

> Draw a mechanism for the following transformation: ОPP OPP ОPP

> Determine whether each of the following compounds is a terpene: OH (a) OH (b) он OH (c) (d)

> Circle the isoprene units in each of the following compounds: он (a) Menthol (b) Grandisol (c) Carvone

> Draw the product of the Robinson annulation reaction that occurs when the following compounds are treated with aqueous sodium hydroxide:

> Classify each prostaglandin according to the instructions provided in Section 26.7. но .COOH .COOH но (Ь) он он (a)

> The following compounds are steroids. One is an anabolic steroid called oxymetholone and the other, called norgestrel, is used in oral contraceptive formulations. Identify which compound is likely the contraceptive based on its structural features (funct