(a) Illustrate the following reactions giving suitable example in each case:

(i) Hoffman Bromide Degradation reaction.

(ii)Diazotization

(iii) Gabriel Phthaliamide Synthesis

(b) Distinguish between the following pair of compounds:

(i)Aniline and N-methylaniline

(ii) (CH3)2NH and (CH3)3N

OR

(a) write the structures of main products when benzene diazonium chloride (C6H5N2+Cl-) reacts with the following reagents

(i) CuCN/KCN

(ii) H₂O

(iii) CH₃CH₂OH

(b) Arrange the following:

(i) C₂H₅NH₂, C₂H₅OH, (CH₃)₃N – in the increasing order of their boiling point.

(ii) Aniline, p-nitroaniline, p-methylaniline-in the increasing order of their basic strength.

(a)

(i) Hoffman Bromide Degradation involves degradation of amide. When any amide is treated with Bromine in the presence of aqueous solution of sodium hydroxide, a primary amine containing 1 less carbon than no. of carbons present in amide, is produced. This reaction is popularly known as Hoffman Bromide Degredation.

RCONH₂ + Br₂ + 4NaOH → R-NH₂ + Na₂CO₃ + 2NaBr + 2 H₂O

(ii) Diazotization reaction is a method of preparation of diazzonium salt from primary aromatic amines. It is one of the very important reactions of organic chemistry. As they can easily undergo coupling reactions to form azo dyes and other important compounds.

In this the primary amines are treated with Nitrous acid in presenence of sodium nitrite (NaNO₂ and a strong HX acid.)

(iii)it is a reaction used to convert primary alkyl halides into primary amines. In this reaction the phthalimide is first treated with KOH which yields an intermediate imide which on further reaction with alky halide give n-alkylphthalimide which on firther reaction with aq NaOH yields primary amine.

(b)

(i)

From the structures we can see that aniline is a primary aromatic amine whereas N-methylaniline is a 2° amine which s responsible for the different chemical properties of these two. Carbylamines test can be used to distinguish between these two. Aniline being a 1° amine will give foul smelling isocyanides but N-methylamine will not.

(ii) (CH₃)₂NH is a 2° amine whereas (CH₃)₃N is a 3° amine. Due to this they have very different chemical property. 2° amines on reaction with nitrous acids produces nitrosamines which are insoluble in mineral acids whereas the 3° amines yields soluble mineral salts on reaction with nitrous acid.

OR

(a). (i) it results in the formation of benzyl nitrile. The Cl^- of benzene diazzonium chloride is replaced by CN group and N₂⁺ is released in the form of N₂ gas.

(ii) on reaction with H₂O, benzene diazzonium salts yields phenol with HCl and Nitrogen gas as byproducts.

(iii) on reaction with ethanol, it yields benzene with acetaldehyde, HCl and Nitrogen gas as byproducts. This reaction is also known as deamination reaction.

(b) (i)

The hydrogen bonding efficiency in amines is great in primary amines due to presence of 2H , better than secondary amines which have only 1 H, and there is no H bonding in tertiary amines due to absence of H atoms. And as we know H bonding provides stability to molecule and hence increases the boiling point. So the order of boiling point will be:

C₂H₅NH₂ > C₂H₅OH > (CH₃)₃N

(ii) The basic strength of any compound is directly proportional to its electron density. CH₃ is an electron releasing group and shows +I effect which increases the electron density of the compound and hence make it more basic. NO₂ group is an electron withdrawing group and hence decreases the electron density and acid strength. So the order of basic strength will be a follow:

p-nitroaniline < Aniline < p-methylaniline