Question

Pentan-2-one is obtained from
(A) 2,2-Dichloropentane
(B)3,3-dichloropentane
(C)Pentan-3-ol
(D)Pent-2-yne

Answer 1

Hint: Methyl propyl ketone which is the other name for Pentan-2-one, can be prepared from the reactant by undergoing hydration followed by dehydration reaction. Hydration reaction involves the addition of water molecules and dehydration involves the removal of water molecules.

Complete step by step answer:
Pentan-2-one is also known as methyl propyl ketone. Pent-2-one can be prepared from 2,2-Dichloropentane. In this reaction, the reactant contains two chlorine atoms. The reactant will undergo hydrolysis to give Pentane-2,2-diol. This happens when the chlorine atoms present in 2,2-Dichloropentane are replaced by the -OH group in order to give Pentane-2,2-diol. Hydration is a process which involves the addition of the water molecule.
Further the formed pentane-2,2-diol will undergo dehydration reaction. Dehydration is a process that involves removal of the water molecule. It will remove the water molecule and ketone will be formed. The product formed is Penan-2-one.
The reaction is given below:

Therefore, the reactant used for the preparation of Pent-2-one is 2,2-Dichloropentane.

Hence the correct answer is option (A) 2,2-Dichloropentane.

Additional information:
Characteristics of Pentan-2-one are given below. They are:
- It is a colourless liquid.
- It has a pleasant ethereal odour.
- The flash point is \[45^\circ F\].
- It is present naturally in Nicotiana tabacum, which is also known as Tobacco.
- It is a less dense liquid which is soluble in water.

Notes: Ketones can be prepared from various methods such as:
- It can be prepared from acyl chloride.
- Oxidation of secondary alcohol.
- Dehydration of alkynes.
- Friedel crafts acylation.
- dehydrogenation of secondary alcohols.