5029

The heat of hydrogenation of trans-2-butene [–27.6 Kcal m^–1] is less than that of propene [–30.1 Kcal m^–1], which is less than that of ethene [–32.8 Kcal m^–1]. Explain the order of stability.

5065

(a) Draw wedge-dash stereochemical formulas for the products that would be obtained from the addition of bromine to Z-2-phenyl-2-butene, and indicate which is the result of syn addition and which is the result of anti addition.

(b) Use a Newman projection formula to show why the product of anti addition predominates.

5066

Draw the structure(s) of the main organic product(s) formed in the following reactions.

(a)

(b)

(c)

(d)

(e)

(f)

(g)

(h)

(i)

5070

The addition of HCl to 3-butene-2-one yields 4-chloro-2-butanone. Account for the formation of this anti-Markovnikov product.

5113

Bromination of Z-1-phenyl-1-propene in acetic acid at 25° gives 17% (RS, SR) and 83% (RR, SS) 1,2-dibromo-1-phenylpropane. Bromination of E-1-phenyl-1-propene under the same conditions leads to a mixture of 73% (RS, SR) and 27% (RR, SS) diastereomers of the same product. Using structures, rationalize these results in terms of mechanism and stereochemistry.

5266

Suggest the major addition product that will be formed the following reaction.

5267

Account for the fact that the acid-catalyzed hydration of isobutylene (2-methylpropene) is considerably faster that the hydration of propylene under similar conditions. Use structures to illustrate your answer, and show how Hammond's Postulate is involved in your conclusion.

5288

(a) The addition of hydrogen bromide to 2-butene, hydrobromination, produces a single product with a molecular formula (C₄H₉Br). Suggest a structural formula for this product and give its IUPAC name.

(b) The addition of hydrogen bromide to 1-butene leads to two different products (C₄H₉Br) depending on the reaction conditions. The isomers differ only in the position of the bromine atom. Suggest a structural formula for each product and give the IUPAC names of the products.

5325

Hydration of 2-methylpropene produces exclusively 2-methyl-2-propanol. Hydration of Z-1,2-dimethylcyclohexene by water in mineral acid at 28° produces a mixture of cis-1,2-dimethylcyclohexanol (45%) and trans-1,2-dimethylcyclohexanol (55%). What do these results say about the regiospecific and stereospecific nature of the acid catalyzed hydration reaction? Be specific and use equations to illustrate your comments.

5382

The regiospecific addition of HI to N,N,N-trimethylethenylammonium iodide violates the classical statement of Markovnikov's rule. Provide a modern interpretation of the direction of addition in this case.