Consider the following reaction
`CHCH + H_2O gives X`
product formed in the given reaction is

Options

A. benzaldehyde
B. acetaldehyde
C. ethanoic acid
D. ethanoyl chloride

Answer

To solve the problem, we need to analyze the reaction of acetylene (CH≡CH) with water (H2O) and determine the product formed.

### Step-by-Step Solution:

1. **Identify the Reactants**: The reactants in the reaction are acetylene (CH≡CH) and water (H2O). Acetylene is an alkyne with a triple bond between the two carbon atoms.

2. **Understand the Reaction Type**: The reaction of acetylene with water is an addition reaction. Specifically, it is an electrophilic addition reaction where water adds across the triple bond of acetylene.

3. **Electrophilic Addition Mechanism**: In this reaction, the π bond of the triple bond (C≡C) is broken, and an electrophile (H⁺ from H2O) attacks one of the carbon atoms. The other part of water (OH⁻) will then bond with the other carbon atom.

4. **Formation of Enol**: The initial product formed after the addition of water is called an enol. The structure of the enol formed from acetylene will be:
- CH2=CHOH (where one carbon has a double bond with another carbon and is bonded to an OH group).

5. **Tautomerization to Keto Form**: The enol form is usually less stable than the keto form. The enol can undergo tautomerization, which is a rearrangement of the molecule to form a more stable keto form. In this case, the enol (CH2=CHOH) will rearrange to form acetaldehyde (CH3CHO), which is the keto form.

6. **Final Product**: The final product of the reaction of acetylene with water is acetaldehyde (CH3CHO).

### Conclusion:
The product formed in the reaction `CH≡CH + H2O` is acetaldehyde (CH3CHO).

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