Question

What are the products of the following reactions? Show all stereoisomers that are formed.

a)

b)

c)

d)

Short answer

a)

b)

c)

d)

Step-by-step solution

Step1:

The Carbonyl group is an important functional group in organic chemistry. There are so many reactions involving this functional group. The carbon of the carbonyl group is electrophilic in nature therefore, undergoes nucleophilic addition reactions.

Formation of the following products

a)

In this (CH₃)₂ is known as Gilman reagent. Treatment of 2-cyclohexanone with Gilman reagent forms a racemic mixture of (S)-3-methyl cyclohexanone and (R)-3- methyl cyclohexanone as follows:

Formation of the desired product (a)

In the above reaction, 1,4 addition product is formed rather than 1,2 addition because in the presence of Gilman reagent 1,4 addition or conjugate addition dominates over 1,2 addition.

b)

In this CH₃MgBr is known as the Grignard reagent. Treatment of 2-cyclohexanone with Grignard reagent followed by hydrolysis results in the formation of (R)-1-methylcyclohex-2-enol and (S)-1-methylcyclohex-2-enol.

Formation of the desired product (b)

c)

When a secondary amine reacts with a ketone, there will be no hydrogen attached to positively charged nitrogen therefore, hydrogen will be removed from carbon directly attached to carbonyl carbon that is hydrogen resulting formation of enamine. Therefore, the reaction of propiophenone with pyrrolidine in the presence of acid forms (Z)-1-(1-phenylprop-1-en-1-yl) pyrrolidine and (E)-1-(1-phenylprop-1-en-1-yl) pyrrolidine as follows:

Formation of the desired product (c)

d)

Sodium borohydride is a selective reducing agent for carbonyl compounds to corresponding alcohols. Thus, 3-heptanone reacts with sodium borohydride in the presence of water to give 3-heptanol. Due to the formation of asymmetric center racemic mixture of (S)-heptan-3-ol and (R)-heptan-3-ol as follows:

Formation of the desired product (d)