Question

Explain with reasons: 
(i) Sulphuric acid is not used in the reaction of alcohol and KI. 
(ii) Haloalkanes form alkyl cyanide as chief product on reaction with KCN, while isocyanide as chief product on reaction with AgCN. 
(iii) Although chlorine is an electron withdrawing group, even then it is ortho- and para-directing in aromatic electrophilic substitution reactions.

Hint:

Electron-withdrawing groups are usually meta-directing, but chlorine's lone pair allows it to also be ortho- and para-directing.

Answer 1

(i) Sulphuric Acid is not used in the reaction of alcohol and KI:
Sulfuric acid is not used in the reaction of alcohol and KI because it is a strong acid and can react with the iodine, forming sulfur dioxide and water. This would reduce the amount of iodine available for the reaction with the alcohol. A mild acid like acetic acid is used instead to promote the reaction without interfering with iodine.
(ii) Haloalkanes form alkyl cyanide as chief product on reaction with KCN, while isocyanide as chief product on reaction with AgCN:
When haloalkanes react with KCN, the cyanide ion (\(\text{CN}^-\)) directly attacks the electrophilic carbon in the haloalkane, leading to the formation of alkyl cyanide. In contrast, when the same reaction occurs with AgCN, the silver ion (Ag\(^+\)) coordinates with the cyanide ion, causing a rearrangement to form an isocyanide (also known as isonitrile). This rearrangement is facilitated by the interaction of the cyanide ion with the silver ion.
(iii) Chlorine is an electron withdrawing group, yet it is ortho- and para-directing in aromatic electrophilic substitution reactions:
Chlorine is an electron-withdrawing group via induction (due to its electronegativity), but it is also an electron-donating group through resonance (due to the lone pair of electrons on the chlorine atom). This electron donation via resonance makes the ortho- and para-positions of the aromatic ring more reactive to electrophilic substitution reactions, which is why chlorine is ortho- and para-directing in these reactions.