NTA Abhyas NEET2020ChemistryAminesPractice
State which of the following statements are true: (i) p K b value for aniline is less than that for methylamine. (ii) Methylamine in water reacts with ferric chloride to give a precipitate of ferric hydroxide. (iii) Aniline does not undergo Friedel-Crafts reaction.
Options
- A(i), (ii), (iii)
- B(ii), (iii)
- C(i), (iii)
- D(i), (ii)
Correct answer
B. (ii), (iii)
Step-by-step solution
(i) False: In aniline, the lone pair of electrons on the N-atom is delocalized over the benzene ring. As a result, electron density on the nitrogen decreases. In contrast, in methylamine C H 3 N H 2 + I effect of methyl group ( C H 3 ) increases the electron density on the N–atom. Therefore, aniline is a weaker base than methylamine and hence its p K b value is higher than that of methylamine. (ii) True: Methylamine being more basic than water, accepts a proton from water liberating O H − ions. These O H − ions com