Question

When pent-2-yne reacts with mercuric sulfate in dilute sulfuric acid, the product is a mixture of two ketones. Give the structures of these products, and use mechanisms to show how they are formed.

Short answer

Ketone is the organic compound with a carbonyl functional group with a carbon attack to double bond oxygen (C=O). The chain is attached to two carbon groups at either side of carbonyl carbon.

Ketones are important in biochemistry and drug treatment used in anti-inflammatory medication.

Step-by-step solution

Step-by-Step SolutionStep 1: Ketone

Ketone is the organic compound with a carbonyl functional group with a carbon attack to double bond oxygen (C=O). The chain is attached to two carbon groups at either side of carbonyl carbon.

Ketones are important in biochemistry and drug treatment used in anti-inflammatory medication.

 Forming a mixture of two ketone

The reaction of pent-2-yne with a mixture of mercuric sulfate in dilute sulfuric acid hydration reaction happen which initially give vinyl alcohol that quickly rearranges to give the mixture of two ketones: pent-3-one and pent-2-one

Formation of the mixture of ketone

Mechanism of the reaction forming mixture of two ketone

Electrophile addition of mercuric ion gives a vinyl cation. There is the possibility of forming two carbocations ( ${\text{2}}^{\text{0}}$vinyl carbocation). Both react with water and lose a proton to give organomercurial alcohol.

Formation of organomercurial alcohol

Under the acidic condition, ${\text{H}}^{\text{+}}$from ${\text{H}}_{\text{2}}{\text{SO}}_{\text{4}}$, mercury is replaced by hydrogen to give vinyl alcohol called enol, which is unstable form. Thus, isomerize to the keto form giving the mixture of ketone pent-3-one and pent-2-one.

Mechanism showing the formation of a mixture of ketone