Question

account for the sunlight is necessary for the substitution reaction of saturated hydrocarbons.

Answer 1

there are some compounds which undergo substitution reaction while other undergo addition reaction. They all have their own importance in synthesis of chemical compounds.The unsaturated compounds containing double and triple bonds i.e. alkenes and alkynes donot undergo substitution reaction, they undergo addition reaction and the saturated compounds containing single bonds i.e. alkanes undergo substitution reaction.Hope it is clear to you.e.g.Example − Halogenation, of Saturated compounds is a substitution reaction.Halogenation of unsaturated hydrocarbons is an addition reaction.Bromine and chlorine react with alkene to form vicinal dihalides (iodine does not undergo addition reaction under normal conditions).

Answer 2

Sunlight is necessary for substitution reaction

Explanation:

• Saturated hydrocarbons undergo substitution reaction through a mechanism called “free radical mechanism”, where the initial step of the reaction is the formation of free radicals. The generation of free radicals requires sunlight, without which the reaction does not get initiated. So, sunlight is necessary for the substitution reactions of saturated hydrocarbons.
• Substitution reactions like chlorination or bromination of alkanes occur within the presence of sunlight. Because these are free radicals substitution reactions. And free radicals are generated in the presence of sunlight or ultraviolet light. ultraviolet light breaks down the halogen or halogen molecule into free radicals and reaction gets initiated. So this reaction cannot take place in a lab.