Q2 of 46 Page 1

Arrange the following in increasing order of pKb values: C6H5CH2NH2, C6H5CH2NHCH3, C6H5NH2

The compound which is more basic have high value of Kb and a lower value of pKb (as Kb ).


In aryl amines the lone pair on N is in conjugation with the benzene ring making benzene ring as EWG and thus the lone pair on N will be less available for protonation. Hence, aryl amines are less basic and C6H5NH2 will be least basic.


In C6H5CH2NH2, benzene ring is not directly attached to N thus the lone pair on N will not be in conjugation with benzene ring electrons thereby increasing its basicity.


In C6H5CH2NHCH3 , benzene ring is not directly attached to N thus the lone pair on N will not be in conjugation with benzene ring electrons. Also, a methyl group is attached to N which will act as EDG which will further increase its basicity.


Order of Kb - C6H5NH2> C6H5CH2NH2 > C6H5CH2NHCH3


Order of pKb- C6H5CH2NHCH3 > C6H5CH2NH2 > C6H5NH2


More from this chapter

All 46 →
26

(a) How do you convert the following:

(i) Phenol to anisole


(ii) Ethanol to propan-2-ol


(b) write the mechanism of the following reaction:



(c) Why phenol undergoes electrophilic substitution more easily than benzene?


OR


(a) Account for the following:


(i) O-nitrophenol is more steam volatile than p-nitrophenol


(ii) T-butyl chloride on heating with sodium methoxide gives 2-methylpropene instead of t-butylmethylether.


(b) Write the reaction involved in the following:


(i) Reamer-Tiemann reaction


(ii) Friedel-Crafts alkylation of phenol


(c) Give simple chemical test to distinguish between ethanol and phenol.


 27

(a) Give reasons for the following:

(i) Sulphur in vapour state shows paramagnetic behaviour


(ii) N-N bond us weaker than P-P bond


(iii) Ozone is thermodynamically less stable than oxygen.


(b) Write the name of gas released when Cu is added to


(i) Dilute HNO3


(ii) Conc. HNO3


OR


(a) Answer the following:


(i) Write the disproportionation reaction of H3PO3


(ii) Draw the structure of XeF4


(b) Account for the following:


(i) Although fluorine has less negative electron gain enthalpy yet F2 is strong oxidising agent.


(ii) Acidic character decreases from N2O3 to Bi2O3


(c) Write a chemical reaction to test sulphur dioxide gas. Write chemical equation involved.


 3

What type of colloid is formed when a liquid is dispersed in a solid? Give an example.

 4

Out of chlorobenzene and p-nitrochlorobenzene, which one is more reactive towards nucleophilic substitution reaction and why?