The total number of σ and π bonds present in the product when propyne is added withwater in presence of 1% H2SO4 and 40% HgSO4

Question

The total number of σ and π bonds present in the product when propyne is added withwater in presence of 1% H2SO4 and 40% HgSO4

Accepted Answer

After hydration of propyne, the product is acetone. It has 9 sigma (σ) bonds and 1 pi (π) bond.

Step 1: Identify the reaction and the main product

The starting alkyne is propyne, CH₃–C≡CH (also called methylacetylene). When you add water in the presence of 1% sulfuric acid (H₂SO₄) and 40% mercuric sulfate (HgSO₄), you carry out the classic acid–mercury-catalyzed hydration of a terminal alkyne. This reaction follows Markovnikov addition and goes through an enol intermediate that rapidly tautomerizes to a ketone.

For a terminal alkyne like propyne, the final stable product is the ketone acetone (also called propan-2-one): CH₃–CO–CH₃.

Net transformation: CH₃–C≡CH + H₂O ⟶ CH₃–CO–CH₃ (acetone).

Step 2: Draw or visualize the product

The product acetone has three carbon atoms. The middle carbon is the carbonyl carbon and is double-bonded to oxygen. Each side of this central carbon is attached to a methyl group (CH₃).

So the skeleton is CH₃–C(=O)–CH₃. This layout makes it easy to count sigma and pi bonds.

Step 3: Count σ and π bonds in acetone

C–H bonds: Two CH₃ groups give 6 C–H single bonds. Each single bond is one σ bond. → 6 σ
C–C bonds: There are two single bonds from the carbonyl carbon to each methyl carbon. Each is one σ bond. → 2 σ
C=O bond: One double bond equals one σ + one π. → 1 σ and 1 π