HC$\equiv$CH+$H_{2}O\frac{{Hg}^{2+}/H^{+}}{\Delta}$ product of the reaction is:

Question

Accepted Answer

The reaction in question involves the addition of water (H₂O) to acetylene (HC≡CH) in the presence of mercury(II) ions (Hg²⁺) and an acidic medium (H⁺), with heat (Δ) applied. This is a classic example of the hydration of alkynes, specifically acetylene, which leads to the formation of an aldehyde.

1. **Explanation for Option 3 ($CH_{3}-C(O)-H$):**

- The reaction mechanism involves the addition of water across the triple bond of acetylene. In the presence of Hg²⁺ and H⁺, acetylene undergoes hydration to form an enol intermediate. This enol is unstable and quickly tautomerizes to form an aldehyde.
   - The enol formed from acetylene is vinyl alcohol (CH₂=CHOH), which tautomerizes to form acetaldehyde (CH₃CHO), also represented as $CH_{3}-C(O)-H$.
   - This process is known as keto-enol tautomerism, where the enol form (vinyl alcohol) converts to the more stable keto form (acetaldehyde).

2. **Explanation for why other options are incorrect:**

- **Option 1 ($CH_{3}CH_{2}OH$):** This option represents ethanol, which is not formed in this reaction. Ethanol would require the reduction of acetaldehyde or the direct hydration of ethylene, not acetylene.
   
   - **Option 2 ($CH_{3}-C(O)-CH_{3}$):** This option represents acetone, a ketone. The hydration of acetylene cannot directly produce a ketone like acetone. Ketones are typically formed from the hydration of internal alkynes, not terminal ones like acetylene.
   
   - **Option 4 ($CH_{3}-C(O)-OH$):** This option represents acetic acid. The formation of acetic acid would require further oxidation of acetaldehyde, which is not part of the given reaction conditions. The reaction conditions specified (Hg²⁺/H⁺) do not facilitate such oxidation.

In conclusion, the correct product of the reaction is acetaldehyde, represented by Option 3 ($CH_{3}-C(O)-H$), due to the hydration of acetylene and subsequent tautomerization of the enol intermediate.