Chapter 17, Problem 26P

Interpretation Introduction

Interpretation:

The principal organic products formed in each of the given reactions are to be identified.

Concept Introduction:

In the ${\text{E}}_{\text{2}}$ reaction mechanism, the abstraction of proton by a base takes place from the molecule that possesses a leaving group such as halide.

The naming of chiral center and geometric isomers are based on Cahn-Ingold-Prelog priority rules. According to these rules, if the priority assigned to each group attached to the chirality center in a molecule is in a clockwise direction, then it is the R-stereoisomer.

Tosylate is a good leaving group. Tosylate leaves a pair of electrons followed by the nucleophilic attack on the reacting molecule to form a new $\text{C}-\text{S}$ bond.

Lithium aluminum hydride is a strong reducing agent. Alcohols or ethers are the functional groups that involve $\text{C}-\text{O}$, $\text{σ}$ bonds.

Oxirane that is commonly called as ethylene oxide is a cyclic ether. Oxirane that is commonly called as ethylene oxide is a cyclic ether.

Answer to Problem 26P

Solution:

a) The principal organic products of the given reaction are as follows:

b) The principal organic products of the given reaction are as follows:

c) The principal organic product of the given reaction is as follows:

d) The principal organic product of the given reaction is as follows:

e) The principal organic product of the given reaction is as follows:

f) The principal organic product of the given reaction is as follows:

g) The principal organic product of the given reaction is as follows:

h) The principal organic product of the given reaction is as follows:

i) The principal organic product of the given reaction is as follows:

j) The principal organic product of the given reaction is ${\text{CH}}_{\text{3}}{{\text{(CH}}_{\text{2}}\text{)}}_{\text{16}}{\text{CH}}_{\text{2}}{\text{SCH}}_{\text{2}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{3}}$.

k) The principal organic product of the given reaction is as follows:

Explanation of Solution

a) Principle organic product formed in the given reaction.

The starting reagents of the given reaction are bromocyclohexane and sodium butan-2-olate. Sodium butan-2-olate is a strong base and bromocyclohexane is a secondary alkyl bromide. Therefore, ${\text{E}}_{\text{2}}$ reaction mechanism is preferred. The complete chemical reaction is shown below.

b) Principle organic product formed in the given reaction.

The starting reagents of the given reaction are iodoethane and sodium-(R)-butan-2-olate. They react with each other to form (R)-2-ethoxybutane and sodium iodide. The complete chemical reaction is shown below.

c) Principle organic product formed in the given reaction.

The starting reagent of the given reaction is a halohydrin, 1-bromobutan-2-ol which reacts with a base to form 2-ethyloxirane. The complete chemical reaction is shown below.

d) Principle organic product formed in the given reaction.

The starting reagent of the given reactions are prop-1-enylbenzene and perbenzoic acid. They react with each other to form 2-methyl-3-phenyloxirane. The complete chemical reaction is shown below.

e) Principle organic product formed in the given reaction.

The starting reagent of the given reactions is an epoxide. It reacts with ${\text{NaN}}_{\text{3}}$ and dioxane-water to form a new $\text{C}-\text{N}$ bond. The complete chemical reaction is shown below.

f) Principle organic product formed in the given reaction.

In the presence of the base ammonia, opening of the epoxide ring takes place at less substituted carbon. The complete chemical reaction is shown below.

g) Principle organic product formed in the given reaction.

Sodium methoxide is a strong base and in the presence of this strong base and methanol, opening of the epoxide ring takes place at less substituted carbon. The complete chemical reaction is shown below.

h) Principle organic product formed in the given reaction.

Hydrochloric acid is a strong acid and in the presence of this strong acid and ${\text{CHCl}}_{\text{3}}$, opening of the epoxide ring takes place at more substituted carbon. The complete chemical reaction is shown below.

i) Principle organic product formed in the given reaction.

Lithium aluminium hydride is a strong base and in the presence of this strong base and diethyl ether, opening of the epoxide ring takes place at less substituted carbon. The complete chemical reaction is shown below.

j) Principle organic product formed in the given reaction.

The given starting material is a tosylate. It is a good leaving group. It leaves with a pair of electrons followed by the nucleophilic attack on sodium butane thiolate to form a new $\text{C}-\text{S}$ bond. The complete chemical reaction is shown below.

${\text{CH}}_{\text{3}}{{\text{(CH}}_{\text{2}}\text{)}}_{\text{16}}{\text{CH}}_{\text{2}}\text{OTs}+{\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{2}}\text{SNa}\to {\text{CH}}_{\text{3}}{{\text{(CH}}_{\text{2}}\text{)}}_{\text{16}}{\text{CH}}_{\text{2}}{\text{SCH}}_{\text{2}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{3}}$

k) Principle organic product formed in the given reaction.

The given starting material is a secondary alkyl halide. It reacts with ${\text{C}}_{\text{6}}{\text{H}}_{\text{5}}\text{SNa}$ to form the product shown below. The complete chemical reaction is,