Question

Correct order for reaction with alcoholic KOH.

A. a>b>c>d
B. a>c>b>d
C. d>b>c>a
D. a>d>b>c

Answer 1

Hint: Alcoholic KOH is used for dehydrogenation. A molecule of hydrogen halide is lost from alkyl halide to form alkene.
Alkyl halides are compounds in which one or more hydrogen atoms in an alkane have been replaced by hydrogen atoms (fluorine, chlorine, bromine and iodine).

Complete step by step answer:
In alkyl halide, polarity of $C - X$ bond increases with increase in chain strength whereas $X$ is any Halogen atom attached to Carbon.

The strength and length of the carbon halogen bond, the dipole moment and the boiling point of an alkyl halide are determined by the polarity of the bond as well as size of various halogen atoms.
The $C - X$bond strength decreases with an increase of size of the halogen because size of p orbital of the halogen increases as well. Thus, the p orbital becomes more diffused and the overlap with the orbital of carbon deteriorates.
As a result, $C - X$ bond is weak and elongated.

Hence due to this reason the correct order of reaction with alcoholic KOH will be a>c>b>d

SO, the correct answer is B.

Note:
The polarity of the $C-X$ bond causes a measurable dipole moment. The chemical behavior of alkyl halide is determined mainly by the electrophilicity of the carbon. The boiling point of the alkyl halides are considerably higher than those of the corresponding alkanes.
Alcoholic KOH dissociates in water to give RO- ions which is a strong base and abstract hydrogen giving rise to elimination in reaction.