Q20 of 26 Page 1

Give reasons for the following :

(a) Methyl amine in aqueous solution gives reddish brown precipitate with ferric chloride (FeCl3).


(b) Ethyl amine is a stronger base than ammonia.


(c) (CH3)3C—NH2 has a lower boiling point than CH3CH2CH2CH2 — NH2 although both are isomeric in nature.


(a) Due to +I effect of CH3 in methyl amine, it is a more basic than water and hence when dissolved in water, it disassociates water in H+ and OH- ions. The OH- ions get attached to Fe of FeCl3 and hence produce Fe3O4 which is responsible for the reddish brown ppt.


(b) Ethyl group due to enhanced +I effect increases the electron density on amine in comparison to H of ammonia group making it more basic than ammonia.


(c) (CH3)3C—NH2 is a 3° amine whereas CH3CH2CH2CH2 — NH2 is a 1° amine. Due to absence of H bonding in 3° amine it is less stable than 1° due to which it has a lower boiling point than 1°.


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