Question

In each reaction box, place the best reagent and conditions from the list below. (A reagent may be used more than once.) Hint: step 1 is conducted at -78°C.

Answer 1

Concepts and reason

The concept used to solve this question is formation of a ketone by the series of reactions between ester and organolithium compound to produce an alcohol and then the oxidation of the alcohol.

Organolithium reagent acts as a nucleophile, attacks the carbonyl carbon, to form an intermediate metal alkoxide salt. Acidic work up converts the metal alkoxide salt into an alcohol which is then oxidized to the carbonyl compound by an oxidizing agent.

Fundamentals

DIBAL-H at $- 70^\circ {\rm{C}}$ reduces esters to corresponding aldehydes.

Aldehydes react with organolithium reagent to give either primary alcohol or secondary alcohols. The number of carbon atoms in the alcohol formed is equal to the sum carbon atoms in the carbonyl compound and the organolithium reagent.

The general formula of a organolithium reagent is ${\rm{RLi}}$ , in which R is an alkyl/aryl group, ${\rm{Li}}$ is a metal. The alkyl group acts as a nucleophile.

Reaction of aldehydes with organolithium reagent followed by the hydrolysis forms an alcohol (new ${\rm{C}} - {\rm{O}}$ bond in the product).

Jones reagent $\left( {{\rm{Cr}}{{\rm{O}}_3},{{\rm{H}}_2}{\rm{S}}{{\rm{O}}_4}} \right)$ is an oxidizing agent that oxidizes primary alcohol to aldehydes and secondary alcohols to ketones.

The reaction for the reduction of methyl acetate to acetaldehyde is as follows:

The reaction for the nucleophilic attack of phenyllithium on acetaldehyde to produce the alcohol is as follows:

Oxidation of alcohol produces the desired product (acetophenone).

The reaction is as follows:

Ans:

The complete reaction for the conversion of the given reactant to product is as follows: