Compounds Containing Nitrogen

The correct answer is Option B: C₆H₅SO₂Cl.

Hinsberg's reagent is benzenesulfonyl chloride (C₆H₅SO₂Cl). It is used to differentiate primary, secondary, and tertiary amines.

Here's why the other options are incorrect :

• Option A: C₆H₅COCl is benzoyl chloride, a reagent used in Friedel-Crafts acylation reactions.


• Option C: SOCl₂ is thionyl chloride, a reagent used to convert alcohols into alkyl chlorides.


• Option D: (COCl)₂ is oxalyl chloride, a reagent used for the conversion of carboxylic acids into acid chlorides.

All the given compounds are acid derivatives, thus contain carbonyl group in them. LiAlH₄ reduces these compounds through nucleophilic substitution via addition elimination (S_NAE) reaction. The rate of reaction depends upon the following factors:

(i) Size of alkyl group.

(ii) Steric hinderance around the > C == O group.

(iii) (+) ve charge on the C-atom of > C == O group.

The alkyl groups are more or less same in the given compounds. Thus, the reactivity order of given compounds depends upon 2nd and 3rd factor written above. The cumulative effect of these two factors results to leaving group ability (LGA) of the substituents in the following order :

This leaving group ability (weak conjugate base) corresponds directly to the reactivity order.

Hence, the correct reactivity order is:

The complete pathway of reactions is as follows :

The basicity of an amine depends on the ability of its nitrogen atom to donate lone pair of electrons in an acid-base reaction. Resonance, inductive effect and steric hindrance etc. plays a very important role in deciding the basicity of compound.

Among the given compounds, (III) is most basic due to the presence of electron donating methyl group which increases the electron density on nitrogen. Compound (IV) is less basic than (III). Hybridisation of nitrogen atom in aniline (I) and pyrrole (II) is sp³ and sp² , respectively, therefore, (I) is more basic than (II). Thus, the correct order of basicity is