Advices For Studying Organic Chemistry

+

H 3 O+

Rδ− δ+

R

R

R

R

RMgX

R

R

MgX

3 o alcohol

R'

C

R"O

O C O

R'

O

MgX

C OH

R'

Ester

R"

Initial product (unstable)

−R"OMgX

spontaneously

R'

C O

Ketone

C OMgX

R'

Salt of an alcohol (not isolated)

1) The initial addition product is unstable and loses a magnesium alkoxide to form

a ketone which is more reactive toward Grignard reagents than esters.

2) A second molecule of the Grignard reagentadds to the carbonyl group as soon as

the ketone is formed in the mixture.

3) After hydrolysis, the product is a 3° alcohol with two identical alkyl groups.

SPECIFIC EXAMPLES
GRIGNARD CARBONYL FINAL
REAGENT REACTANT PRODUCT
Reaction with formaldehyde

+ H^3 O

+

C 6 H 5 MgBr C 6 H 5 C 6 H 5 CH

Benzyl alcohol

(90%)

H

C

H

O CH 2 OMgBr

Fromaldehyde

Et 2 O^2 OH

Phenylmagnesium

bromide

Reaction with a higher aldehyde

+ H^3 O

+

CH 3 CH 2 MgBr CH 3 CH 2 CH 3 CH 2

2-Butanol

(80%)

H 3 C

C

H

O

Acetaldehyde

Et 2 O CHOH

Ethylmagnesium

bromide

C OMgX

CH 3

H

CH 3

Reaction with a ketone