Identify the catalyst $X$ used in the following reaction: $CH_{3}CH_{2}Br + 2[H] \stackrel{X}{\longrightarrow} CH_{3}CH_{3} + HBr$

Which one of the following compounds will be least susceptible to the elimination of hydrogen bromide $(HBr)$?

Arrange the following compounds in order of decreasing rate of hydrolysis for $S_{N}1$ reaction:
$(I) \ C_6H_5-CH_2-Br$
$(II) \ p-CH_3-C_6H_4-CH_2-Br$
$(III) \ p-CH_3CH_2-C_6H_4-CH_2-Br$
$(IV) \ p-(CH_3)_2CH-C_6H_4-CH_2-Br$

An alkyl halide may be converted into an alcohol by

Identify $Z$ in the following series of reactions:

The organic chloro compound,which shows complete stereochemical inversion during an $S_{N}2$ reaction,is