Question

2.3 In the following nitration reaction, when NH4+ (pka = 9.2) was used, the reaction did not proceed and no product was formed Acid HNO3, 50°C ON D B a) Given that the pka of HNO3 is -1.4, explain, in not more than 3 lines, why the reaction did not proceed? (4 marks)

Answer 1

nitration is a substitution reaction in which no2 group is introduced by subsituting h+, so it is a electrophilic substitution reaction , ie, takes place only in presence of a strong elctrophile.

the nitration is only takes place in presence of a strong acid. so it usually takes place in the presence ofHNO₃ and H₂SO₄

a, NH₄⁺ is a weak acid, and is a weak electrophile, it cannot be combined with the strong nucleophile benzyloxybenzene cation. so the reaction with ammonium ion cannot yield a nitrated product.since the pka is high (9.2), it is a weak acid, so the reaction will not be further proceeded.

b,nitration proceeds in the presence of a strong acid. since HI is a very strong acid, having pka of -9.2, it will be the most suitable reagent for nitration to occur.

c,the type of electrophillic aromatic substitution reaction where a nitro group gets substituted with a hydrogen ion is called nitration reaction.

so the elerctrophillic aromatic substitution reaction is nitration.

note: please do like the answer.