Organic Chemistry

Summary of Reactions 775

Nucleophilic addition to the carbonyl carbon of an -
unsaturated Class II carbonyl compound is called direct
addition; addition to the is called conjugate ad-
dition. Whether direct or conjugate addition occurs de-
pends on the nature of the nucleophile, the structure of the
carbonyl compound, and the reaction conditions. Nucleo-
philes that form unstable direct addition products—halide
ions, cyanide ion, thiols, alcohols, and amines—form con-
jugate addition products. Nucleophiles that form stable ad-
dition products—hydride ion and carbanions—form direct

b-carbon

a,b addition products with reactive carbonyl groups and conju-

gate addition products with less reactive carbonyl groups.

A Grignard reagent with a highly polarized bond

reacts with the harder bond; a Gilman reagent

with a less polarized bond reacts with the softer

bond.

Nucleophiles form nucleophilic acyl substitution prod-

ucts with Class I carbonyl compounds that

have reactive carbonyl groups and conjugate addition prod-

ucts with compounds with less reactive carbonyl groups.

a,b-unsaturated

C“C

C¬Cu

C“O

C¬Mg

Summary of Reactions

1. Reaction of carbonyl compoundswith carbon nucleophiles (Section 18.4).

a. Reaction of formaldehydewith a Grignard reagent forms a primary alcohol:

b.Reaction of an aldehyde(other than formaldehyde) with a Grignard reagent forms a secondary alcohol:

c.Reaction of a ketonewith a Grignard reagent forms a tertiary alcohol:

d.Reaction of an esterwith a Grignard reagent forms a tertiary alcohol with two identical substituents:

e.Reaction of an acyl chloridewith a Grignard reagent forms a tertiary alcohol with two identical substituents:

f. Reaction of with a Grignard reagent forms a carboxylic acid:

OOC CH 3 C OH

1. CH 3 MgBr


2. H 3 O+

O

CO 2

RCHC 3

RCl

1. 2 CH 3 MgBr


2. H 3 O+

OH

CH 3

O

C

RCHC 3

ROR′

1. 2 CH 3 MgBr


2. H 3 O+

OH

CH 3

O

C

RRC ′

R R′

1. CH 3 MgBr
   2. H 3 O+

OH

CH 3

O

C

RHC

1. CH 3 MgBr


2. H 3 O+

OH

CH 3

O

H

C

R

O

H

C

H

1. CH 3 MgBr


2. H 3 O+

CH 3 CH 2 OH