Question

What Grignard reagent and what carbonyl compound might you startwith to prepare the following alcohols?

(a)

(b)

(c)

(d)

(e)

(f)

Short answer

(a)

(b)

(c)

(d)

(e)

(f)

(a)

Step-by-step solution

Reaction of Grignard reagent with carbonyl compounds 

Grignard reagents react with formaldehyde to generate a primary alcohols. It reacts with other alcohols to produce secondary alcohols. It reacts with a ketone to give tertiary alcohol.

Grignard reagent and carbonyl compound required to prepare the alcohol

(a)The given compound butan-2-ol can be produced by reacting acetaldehyde with ethyl magnesium bromide or propionaldehyde with methyl magnesium bromide. The reaction can be given as:

Reaction (a)

(b)The given compound, pentan-3-ol can be produced by reacting propionaldehyde with ethyl magnesium bromide. The reaction can be given as:

Reaction (b)

(c)The given alcohol 2-methyl-prop-2-en-1-ol can be produced by reacting 2-methyl-prop-2-en-1-ol with formaldehyde. The reaction can be given as:

Reaction (c)

(d)The given alcohol, triphenylmethanol can be produced by reacting benzophenone with phenyl magnesium bromide or by reacting an aromatic ester with two phenyl magnesium bromide molecules. The reaction can be given as:

Reaction (d)

(e)The given compound, 2-phenylpropan-2-ol can be created by three ways.

In the first method acetophenone is reacted with methyl magnesium bromide to generate 2-phenylpropan-2-ol. In the second method, an aromatic ester reacts with 2 equivalents of methyl magnesium bromide to generate 2-phenylpropan-2-ol. In the third method, phenyl magnesium bromide reacts with propan-2-one to produce 2-phenylpropan-2-ol.

The reaction can be given as:

Reaction (e)

(f)The given compound, cyclohex-1-en-1-ylmethanol can be created by reacting cyclohex-1-en-1-ylmagnesium bromide with formaldehyde. The reaction can be given as:

Reaction (f)