Reaction of 1-Chlorobutane with Alcoholic Potash

The reaction of 1-chlorobutane with alcoholic potash (potassium hydroxide dissolved in alcohol) is an example of an elimination reaction known as dehydrohalogenation. In this reaction, the chlorine atom (halogen) is eliminated from the 1-chlorobutane molecule, resulting in the formation of a double bond between the adjacent carbon atoms.

Mechanism of the Reaction:

1. Formation of Alkoxide Ion:
Alcoholic potash (KOH dissolved in alcohol) reacts with 1-chlorobutane to form an alkoxide ion. The alcohol acts as a solvent and helps in the dissolution of KOH. The alkoxide ion is formed by the nucleophilic attack of the hydroxide ion on the carbon atom bonded to the chlorine atom in 1-chlorobutane. The chlorine atom leaves as a chloride ion.

2. Proton Transfer:
The alkoxide ion formed in the previous step abstracts a proton from the solvent alcohol molecule. This leads to the formation of an alcohol molecule and the deprotonated alkoxide ion.

3. Elimination of Chlorine Atom:
The deprotonated alkoxide ion (an alkoxide ion without a proton) undergoes elimination of the chloride ion, resulting in the formation of a double bond between the adjacent carbon atoms. This step is known as β-elimination or dehydrohalogenation.

Product Formation:

The elimination of the chloride ion leads to the formation of 1-butene as the major product. The double bond is formed between the second and third carbon atoms in the butane molecule.

Explanation of the Correct Answer:

The correct answer to this question is option 'A', which is 1-butene. This is because the elimination of the chloride ion from 1-chlorobutane results in the formation of a double bond between the second and third carbon atoms, leading to the formation of 1-butene. The other options (1-butanol, 2-butene, and 2-butanol) are incorrect because they do not correspond to the product formed in this reaction.

In summary, the reaction of 1-chlorobutane with alcoholic potash leads to the elimination of the chloride ion and the formation of 1-butene as the major product. This reaction is an example of an elimination reaction known as dehydrohalogenation.