Q60E - Organic Chemistry (Mcmurry)

Question

How would you use a Grignard reaction on an aldehyde or ketone to synthesize the following compounds?

1. 2-Pentanol
2. 1-Butanol
3. 1-Phenylcyclohexanol
4. Diphenylmethanol

Step-by-Step Solution

Answer

a) 

b)

c)

d)

Step-by-Step Solution Step 1: Grignard reaction on aldehyde and ketone

The Grignard reaction with aldehyde and ketones gives a different degree of  alcohol. Formaldehyde reaction with Grignard reagent always gives primary alcohols. Secondary and tertiary alcohols are formed by the Grignard reaction of aldehyde and ketones or esters. 

Step 2: The synthesis of 2-Pentanol

(a) The compound 2-Pentanol is a secondary alcohol, and we know secondary alcohols are formed by the reaction of aldehyde and Grignard reagent. Thus, we can use the following aldehydes and Grignard reagents to synthesize 2-pentanol (secondary alcohol). 

                                  Synthesis of 2-Pentanol

Step 3: The synthesis of 1-Butanol

(b) The compound 1-Butanol is a primary alcohol, and we know that primary alcohols are formed by the reaction of formaldehyde with the Grignard reagent. Thus, we can use formaldehyde (HCHO) and ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{2}}\text{MgBr}$(Grignard reagent) to synthesize 1-butanol (primary alcohol).

                                        Synthesis of 1-Butanol

Step 4: The synthesis of 1-Phenylcyclohexanol

(c) The compound 1-Phenylcyclohexanol is tertiary alcohol, and we know tertiary alcohols are formed by the reaction of ketone or ester with the Grignard reagent. Thus, we can use cyclohexanone (ketone) and ${\text{C}}_6{\text{H}}_5\text{MgBr}$(Grignard reagent) to synthesize 1-Phenylcyclohexanol (tertiary alcohol).

                                 Synthesis of 1-Phenylcyclohexanol

Step 5: The synthesis of Diphenylmethanol

(d) The compound Diphenylmethanol is a secondary alcohol, and we know secondary alcohols are formed by the reaction of an aldehyde with the Grignard reagent. Thus, we can use benzaldehyde(aldehyde) and ${\text{C}}_6{\text{H}}_5\text{MgBr}$(Grignard reagent) to synthesize Diphenylmethanol (secondary alcohol).

                                      Synthesis of Diphenylmethanol