8. Elimination Reactions

Draw the substitution and elimination products for the following reactions, showing the configuration of each product:

c. 1-chloro-1-methylcyclohexane + CH₃O⁻

d. 1-chloro-1-methylcyclohexane + CH₃OH

For each of the following reactions, draw the major elimination product; if the product can exist as stereoisomers, indicate which stereoisomer is obtained in greater yield.

a. (R)-2-bromohexane + high concentration of CH₃O⁻

b. (R)-3-bromo-3-methylhexane + CH₃OH

What are the products of the following reactions?

a.

b.

Explain how each of the following changes affect the rate of the reaction of 1-bromobutane with ethoxide ion in DMF.

c. The alkyl halide is changed to 1-chlorobutane.

d. The alkyl halide is changed to 2-bromobutane.

What are the products of the following reactions?

g.

h.

Draw the products of each of the following S_N2/E2 reactions. If the products can exist as stereoisomers, show which stereoisomers are formed.

c. (3S,4R)-3-bromo-4-methylhexane + CH₃O⁻

What products (including stereoisomers, if applicable) are formed from the reaction of 3-bromo-3-methylpentane:

b. with H₂O?

Which of these reactions are likely to produce both elimination and substitution products?

a. 2-bromopentane + NaOCH₃

b. 3-bromo-3-methylpentane + NaOMe. (Me = methyl, CH₃)

c. 2-bromo-3-ethylpentane + NaOH

For each reaction, decide whether substitution or elimination (or both) is possible, and predict the products you expect. Label the major products.

c. chlorocyclohexane+NaOCH₃ in CH₃OH

d. chlorocyclohexane + NaOC(CH₃)₃ in (CH₃)₃COH

Silver-assisted solvolysis of bromomethylcyclopentane in methanol gives a complex product mixture of the following five compounds. Propose mechanisms to account for these products.

(a)

Deuterium (D) is the isotope of hydrogen of mass number 2, with a proton and a neutron in its nucleus. The chemistry of deuterium is nearly identical to the chemistry of hydrogen, except that the C―D bond is slightly (5.0 kJ/mol, or 1.2 kcal/mol) stronger than the C―H bond. Reaction rates tend to be slower if a C―D bond (as opposed to a C―H bond) is broken in a rate-limiting step. This effect on the rate is called a kinetic isotope effect. (Review PROBLEM 4-57)

a. Propose a mechanism to explain each product in the following reaction.

Two stereoisomers of a bromodecalin are shown. Although the difference between these stereoisomers may seem trivial, one isomer undergoes elimination with KOH much faster than the other. Predict the products of these eliminations, and explain the large difference in the ease of elimination.

Make models of the following compounds, and predict the products formed when they react with the strong bases shown.

(b) meso-1,2-dibromo-1,2-diphenylethane + (CH₃CH₂)₃N:

Predict the products and mechanisms of the following reactions. When more than one product or mechanism is possible, explain which are most likely.

e. isobutyliodide + KOH in ethanol/water

f. isobutylchloride + AgNO₃ in ethanol/water

The solvolysis of 2-bromo-3-methylbutane potentially can give several products, ­including both E1 and products from both the unrearranged carbocation and the rearranged ­carbocation. Mechanisms 6-6 and 7-2 show the products from the rearranged carbocation. Summarize all the possible products, showing which carbocation they come from and whether they are the products of E1 or reactions.

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