Hydrocarbons (Alkane, Alkene and Alkyne) MCQ Questions & Answers in Organic Chemistry | Chemistry

The increasing order of reduction of alkyl halides with zinc and dil. $$HCl$$  is $$ R - Cl < R - Br < R - I $$
As the size of the halogen increases down the group, the strength of $$C - X$$  bond decreases, as a result, reactivity increases.

Key Idea Lower hydrocarbons exist in gaseous state while higher ones are in liquid state or solid state.
On cracking or pyrolysis, the hydrocarbon with higher molecular mass gives a mixture of hydrocarbons having lower molecular mass. Hence, we can say that by cracking a liquid hydrocarbon can be converted into a mixture of gaseous hydrocarbons.

It is an example of intramolecular Wurtz reaction $$Na \to N{a^ + } + {e^ - }$$

Peracids gives trans hydroxylated products with alkenes.

Benzene does not show addition reactions like alkenes due to delocalisation of $$\pi $$ - electrons.

Electrophile $$NO_2^ + $$  is generated by the help of $${H_2}S{O_4}.$$   In absence of $${H_2}S{O_4}$$  a nucleophile $$NO_3^ - $$  will be formed which will not be helpful in electrophilic substitution.

$$C{l_2}$$  is added to benzene ring in presence of sunlight to give benzene hexachloride which is a free radical reaction.

Wurtz reaction is used in preparing hydrocarbons by taking two alkyl halides.

The said reactions can be visualised as

Thus, option (C) is correct.