(a) As shown in Fig. P11.78(a) on p. 568, 1,5-cyclooctadiene undergoes an electrophilic

Draw the structure of each of the following. (Some parts may have more than one correct answer.) (a) a nine-carbon ether that cannot be prepared by the Williamson synthesis (b) a nine-carbon ether that can be prepared by the Williamson synthesis (c) a four-carbon ether that would yield 1,4- diiodobutane after heating with an excess of HI (d) an ether that would react with HBr to give propyl bromide as the only alkyl halide (e) a four-carbon alkene that would give different glycols after treatment with alkaline KMnO4 or treatment with meta- chloroperoxybenzoic acid followed by dilute aqueous acid (f) a four-carbon alkene that would give the same glycol as a result of the different reaction conditions in (e) (g) a diene (a compound with two double bonds) C6H8 that can form only one mono-epoxide and two di-epoxides (counting stereoisomers) (h) an alkene C6H12 that would give the same glycol either from treatment with a peroxycarboxylic acid, followed by acid catalyzed hydrolysis, or from glycol formation with OsO4

Give the major organic product of each of the following reactions. Include stereochemistry where relevant. (a) dibutyl sulfide with 1 equivalent of H2O2 at 25 C (b) dibutyl sulfide with 2 or more equivalents of H2O2 and heat (c) cis-3-hexene with magnesium monoperoxyphthalate (MMPP) (d) the product of (c) with (CH3)2CuCNLi2, then H3O+ (e) the product of (c) with solvent H2O in acidic solution (f) the product of (e) with periodic acid (g) the product of (d) with NaH in THF followed by CH3I (h) (E)-3-methyl-3-hexene with Hg(OAc)2 in ethanol solvent followed by NaBH4 (i) the product of (h) with acidic methanol ( j) (R)-3-Methyl-1-bromopentane with Mg in ether, then with ethylene oxide, then with CH3I

Give the products of the reaction of 2-ethyl2-methyloxirane (or other compound indicated) with each of the following reagents. (a) water, H3O+ (b) water, NaOH, heat (c) Na+ CH3O in CH3OH (d) CH3OH and a catalytic amount of H2SO4 (e) dilithium dimethylcyanocuprate, then H3O+ (f) product of part (c) 1 HBr, 25 C (g) product of part (d) 1 HBr, 25 C (h) product of part (c) 1 NaH, then CH3I (i) product of part (d) 1 NaH, then CH3CH2I ( j) product of part (a) 1 periodic acid (k) product of part (f) 1 Mg in dry ether (l) product of part (k) 1 ethylene oxide, then H3O+

Which of the ring-opening reactions given in Fig. P11.47 should occur most readily? Explain.

Which of the ring-opening reactions given in Fig. P11.48 should occur most readily? Explain.

Explain how you could differentiate between the compounds in each of the following pairs by using simple physical or chemical tests that give readily observable results, such as obvious solubility differences, color changes, evolution of gases, or formation of precipitates. (a) 3-ethoxypropene and 1-ethoxypropane (b) 1-pentanol and 1-methoxybutane (c) 1-methoxy-2-methylpropane and 2-chloro-1- methoxy-2-methylpropane

When HCl is formed as a by-product in reactions, it is usually removed from reaction mixtures by neutralization with aqueous base. At times, however, the use of base is not compatible with the products or conditions of a reaction. It has been found that propylene oxide (2-methyloxirane) can be used to remove HCl quantitatively. Explain why this procedure works

A student has run the reactions shown in Fig. P11.51 on p. 562 and is disappointed to find that each has given none of the desired product. Explain why each reaction failed.

Tell whether each of the following compounds can be prepared by the reaction of a Grignard reagent with ethylene oxide. If so, show the reaction; if not, explain why and give a different synthesis that uses a different epoxide starting material. (a) 2-pentanol (b) 1-pentanol

For each of the following alkenes, state whether a reaction with OsO4 followed by aqueous NaHSO3 will give a racemic mixture of products that can (in principle) be resolved into enantiomers under ordinary conditions. (a) ethylene (b) cis-2-butene (c) trans-2-butene (d) cis-2-pentene

The (1)-stereoisomer of 2-methyloxirane reacts with aqueous NaOH to give the (R)-(2)- stereo isomer of 1,2- propanediol. Use this observation to propose the absolute stereochemical configuration of (1)-2-methyl oxirane

Predict the absolute configuration of the major diol product formed by treatment of (S)-2-ethyl-2-methyloxirane with water in the presence of an acid catalyst.

Keeping in mind that many intramolecular reactions that form six-membered rings are faster than competing intermolecular reactions (Sec. 11.8), predict the product of the reaction given in Fig. P11.56.

When (3S,4S)-4-methoxy-3-methyl-1-pentene is treated with mercuric acetate in methanol solvent, then with NaBH4, two isomeric compounds with the formula C8H18O2 are isolated. One, compound A, is optically inactive, but the other, compound B, is optically active. Give the structures and absolute configurations of both compounds. (See Study Guide Link 7.2.)

You are a manager for a company, Weighty Matters, that specializes in the manufacture of organic compounds containing 18O, a heavy isotope of oxygen. You have assigned the task of preparing ether B to a team of two staff experts, and you have stipulated that alcohol A must be used as a starting material (* O 5 18O):A member of your staff, Homer Flaskclamper, has proposed the following two possible syntheses and has come to you for advice. (1) (2) Which synthesis would you advise Flaskclamper to use and why?

Match each of the following four compounds with one of the compounds AD on the basis of the following experimental facts. Compounds A, B, and C are optically active, but compound D is not. Compound C gives the same products as compound D on treatment with periodic acid, but compound B gives a different product. Compound A does not react with periodic acid. (1) (2S,3S)-2,4-dimethoxy-1,3-butanediol (2) meso-1,4-dimethoxy-2,3-butanediol (3) (1)-1,4-dimethoxy-2,3-butanediol (4) (2R,3R)-3,4-dimethoxy-1,2-butanediol

Complete the reactions given in Fig. P11.60 by giving the principal organic products. Indicate the stereochemistry of the products in parts (d), (g), (h), (i), and (k).

Outline a synthesis for each of the following compounds from the indicated starting material and any other reagents. [All chiral compounds should be prepared as racemates except in parts (1) and (m).] (a) 2-ethoxy-3-methylbutane from 3-methyl-1-butene (b) 2-ethoxy-2-methylbutane from 2-methyl-2-butanol (c) 4,4-dimethyl-1-pentanol from ethylene oxide (d)

Outline a synthesis for each of the following compounds in enantiomerically pure form from enantiomerically pure (2R,3R)-2,3-dimethyloxirane: (a) (2R,3S)-3-methoxy-2-butanol (b) (c) CH3CH EtO OMe CHCH3 (2R,3S)- 2 3 (d)

Compound A, C8H16, undergoes catalytic hydrogenation to give octane. When treated with meta- chloroperoxybenzoic acid, A gives an epoxide B, which, when treated with aqueous acid, gives a compound C, C8H18O2, which can be resolved into enantiomers. When A is treated with OsO4 followed by aqueous NaHSO3, an achiral compound D (a stereoisomer of C) forms. Identify all compounds, including stereochemistry where appropriate.

An alternative to the ozonolysis of alkenes is to treat an alkene with two molar equivalents of periodic acid and a catalytic amount of OsO4. (a) Explain the role of each reagent in the reaction shown in Fig. P11.64. Your explanation should account for the fact that two molar equivalents of periodic acid are required. (b) Complete the following reaction.

Give the structures of all epoxides that could in principle be formed when each of the following alkenes reacts with meta-chloroperoxybenzoic acid (mCPBA). Which epoxide should predominate in each case? Why? (a) cis-4,5-dimethylcyclohexene (b)

When CH3CH2SCH2CH2SCH2CH3 .. .. .. .. reacts with two equivalents of CH3I, the following double sulfonium salt precipitates: (a) Give a curved-arrow mechanism for the formation of this salt. (b) Upon closer examination, this compound is found to be a mixture of two isomers with melting points of 123124 C and 154 C, respectively. Explain why two compounds of this structure are formed. What is the relationship between these isomers? (Hint: See Sec. 6.9B.)

When S-adenosylmethionine (Fig. 11.1, p. 537), isolated from natural sources, is allowed to stand in aqueous solution for several weeks at room temperature, a stereoisomeric contaminant appears in solution that can be separated by ordinary methods. Suggest a structure for this contaminant and a reason that it forms. (Hint: No covalent bonds are broken in this process.)

When the naturally occurring amino acid (S)-methionine (see Eq. 11.78, p. 552) is converted into methionine sulfoxide, two isomers with different physical properties are formed. What are their structures and what is their stereochemical relationship

One of the side reactions that occur when epoxides react with OH is the formation of polymers. Propose a mechanism for the following polymerization reaction, using the curved-arrow notation.

(a) Give a curved-arrow mechanism for the reaction shown in Fig. P11.70. Be sure your mechanism indicates the role of the weak acid ammonium chloride. (b) Why does the reaction of an aziridine require this weak acid? (Hint: The pKa of an amine RNH2 is about 32.) (c) The pKa of ammonium ion is 9.25; the conjugate-acid pKa of an aziridine is about 7; and the pKa of HN3 is 4.2. A student has suggested that dilute (0.01 M) HCl should be an even better catalyst. Critique this suggestion

The drug mechlorethamine (mustine) has been used in antitumor therapy. It is one of a family of compounds called nitrogen mustards, which also includes the antitumor drugs cyclophosphamide and chlorambucil. (a) Mechlorethamine undergoes a nucleophilic substitution reaction with water that is several thousand times faster than the nucleophilic substitution reaction of 1,5-dichloropentane. Give the product of the mechlorethamine reaction and the mechanism for its formation. (b) The antitumor effects of mechlorethamine are due to the fact that it crosslinks DNA. (See the vignette on p. 545, particularly Eqs. 11.7011.71.) Show this crosslinking process with the curved-arrow notation, using R3N: to represent a base on DNA.

In each of the following pairs, one of the glycols is virtually inert to periodate oxidation. Which glycol is inert? Explain why. (Hint: Consider the structure of the intermediate in the reaction.)

Account for the following observations with a mechanism. (Refer to Fig. P11.73.) (1) In 80% aqueous ethanol, compound A reacts to give compound B. Notice that trans-B is the only stereoisomer of this compound that is formed. (2) Optically active A gives completely racemic B. (3) The reaction of A is about 105 times faster than the analogous substitution reactions of both its stereoisomer C and chlorocyclohexane.

Provide a curved-arrow mechanism for each of the reactions in Fig. P11.74 on p. 566 that accounts for the stereochemical results. Show the structure of the unstable intermediate in each case and explain why it is unstable.

The reaction of d-chlorobutyl phenyl sulfide in dioxane containing 20 M water at 100 C gives a cyclic compound X that can be isolated. (See Fig. P11.75 on p. 566). This reaction is 21 times faster than the reaction of 1-chlorohexane under the same conditions. (a) Deduce the structure of X and give the curved-arrow mechanism for its formation. (b) Calculate the proximity effect for this reaction. (c) Suggest a reason the proximity effect for this reaction is much smaller than the effect calculated for the similar reaction in Eq. 11.61b (p. 539). (This proximity effect was calculated in Study Problem 11.5.)

One of the reactions given in Fig. P11.76 is about 2000 times faster in pure water than it is in pure ethanol. Another is about 20,000 times faster in pure ethanol than it is in pure water. The rate of the third changes very little when the solvent composition is changed from ethanol to water. Which of the reactions is faster in ethanol, which is faster in water, and which has a rate that is solventinvariant? Explain. The solvent (ethanol, water, or a mixture of the two) in the following equations is indicated by ROH. (Hint: Notice the difference in dielectric constants for ethanol and water in Table 8.2 on p. 355.)

Draw a curved-arrow mechanism for each of the conversions shown in Fig. P11.77 on p. 567. Hint: The structure of the product in part (c) of Fig. P11.76 can also be redrawn as follows:

(a) As shown in Fig. P11.78(a) on p. 568, 1,5-cyclooctadiene undergoes an electrophilic addition with SCl2 to give compound A. (Notice the conformation of A, also shown.) Provide a curved-arrow mechanism for this transformation that accounts for the stereochemistry. (Hint: Start with a simple electrophilic addition of SCl2 to one double bond.) (b) Suggest a mechanism that accounts for the reaction of A shown in Fig. P11.78(b).

Each of three bottles, labeled respectively A, B, and C, contains one of the compounds given in Fig. P11.79 on p. 568. On treatment with KOH in methanol, compound A gives no epoxide, compound B gives an epoxide D, and compound C gives an epoxide E. Epoxides D and E are stereoisomers. Under identical conditions, C gives E much more slowly than B gives D. Identify A, B, and C, and explain all observations.

Two of the compounds given in Fig. P11.80 on p. 568 form epoxides readily when treated with OH, one forms an epoxide slowly, and one does not form an epoxide at all. Identify the compound(s) in each category and explain.

(a) Account for the stereochemical results in the reaction in Fig. P11.81(a) on p. 568 with a mechanism. (Hint: See Study Problem 11.6, p. 547.) (b) What stereochemical result would you expect if the 2S,3S-stereoisomer of 3-bromo-2-butanol undergoes the same reaction?