Q25 of 27 Page 1

(a) Identify A – D


(b) Distinguish between the following pair of compounds:


(i) Aniline and Benzylamine.


(ii) Methylamine and Dimethylamine


(c) Complete the following:



OR


(a) Account for the following:


(i) Direct nitration of aniline yields a significant amount of meta derivative.


(ii) Primary aromatic amines cannot be prepared by Gabriel phthalimide synthesis.


(b) Carry out the following conversions:


(i) Ethanoic acid into methenamine.


(ii) Aniline to p - Bromoaniline.


(c) Arrange the following in increasing order of basic strength: Aniline, p - nitroaniline, and p - toluene.

(a) A = AgNO2


B =


C =


D =


Explanation:


reacts with AgNO2 to give


reacts with tin in an acidic medium to give


reacts with bromine in the presence of NaOH to give


reacts with CHCl3 and KOH to give


(b)


(i)


(ii)


(c) A =


B =


Explanation:


CH3CH2CN


Step 1:Ethane nitrile on reduction with lithium aluminium hydride produces primary amine – propylamine.


Step 2: Propyl amine on reaction with nitrous acid prepared in situ by reaction of sodium nitrite and hydrochloric acid gives propyl alcohol.


OR


(a) (i) The anilinium ion formed in a strongly acidic medium is by the protonation of aniline during nitration os meta - directing.


(ii)


Primary aromatic amines cannot be prepared by Gabriel phthalimide synthesis because aryl halides do not undergo nucleophilic substitution with the anion formed by phthalimide.


(b) (i)



1. Ethanoic acid is first converted into into an ethanamide by the action of ammonia.


2. Hoffman bromamide degradation reaction:


The amide produced from the first step is used to make a primary amine by the Hoffman bromamide degradation reaction. An amide is treated with bromine in an aqueous or ethanolic solution of sodium hydroxide.


In this reaction, an alkyl or aryl group migrates from the carbonyl atom to the nitrogen atom. The amine formed methanamine.


(ii) This reaction can be carried out by a process called bromination. Simple bromination produces only ortho and para products. To produce a product with only a single substituted product, a special reaction is carried out-


The amine is first treated with pyridine to get acetanilide. This reacts with bromine in the presence of ethanoic acid which is then treated in an acidic or alkaline medium to get 4-Bromoaniline.


(c) p – nitroaniline < aniline < p - toluene.


Reason:



IMPORTANT: Basic strength is proportional to the electron-density of the atom


In p-toluene, there is the presence of electron donating CH3 group. This increases the electron-density of the N-atom Therfore p-toluene is more basic than aniline.


The presence of electron-withdrawing group NO2 IN p-nitroaniline decreases the electron density of the N atom, therefore it is less basic than aniline.


Hence the order is Aniline, p - nitroaniline, and p - toluene.


More from this chapter

All 27 →
23

Explain the following:

(a) Out of Sc3 + , Co2 + and Cr3 + ions, Sc3 + only is colorless in aqueous solutions. (Atomic no. : Co = 27; Sc = 21 and C = 24)


(b) The E°Cu2 + /Cu for copper metal is positive ( + 0. 34), unlike the remaining members of the first transition series


(c) La(OH)3 is more basic than Lu(OH)3.

 24

A metal complex having composition Cr(NH3)4Cl2Br has been isolated in two forms A and B. form A reacts with AgNO3 to give a white precipitate readily soluble in dilute aqueous ammonia whereas B gives a pale yellow precipitate soluble in concentrated ammonia.

(i) Write the formulae of isomers A and B.


(ii) State the hybridization of chromium in each of them.


(iii) Calculate the magnetic moment (spin only value) of the isomer.

 26

(a) A cell is prepared by dipping a zinc rod in 1M zinc sulfate solution and a silver electrode in 1M silver nitrate solution. The standard electrode potential is given:
E0Zn2+/Zn = -0.76 V,
 E0Ag2+/Ag = +0.80 V,

What is the effect of an increase in the concentration of Zn2 + on the Ecell?


(b) Write the products of electrolysis of aqueous solution of NaCl with platinum electrodes.


(c) Calculate e. m. f. of the following cell at 298 K:


Ni(s) / Ni2 + (0. 01 M) // Cu2 + (0. 1M) / Cu (s)



Write the overall cell reaction.


OR


(a) Apply Kohlrausch law of independent migration of ions, write the expression to determine the limiting molar conductivity of calcium chloride.


(b) Given are the conductivity and molar conductivity of NaCl solutions at 298K at different concentrations:



Compare the variation of conductivity and molar conductivity of NaCl solutions on dilution. Give reason.


(c) 0. 1 M KCl solution offered a resistance of 100 ohms in a conductivity cell at 298 K. If the cell constant of the cell is 1. 29 cm - 1, calculate the molar conductivity of KCl solution.

 27

(a) Account for the following observations:

(i) SF4 is easily hydrolysed whereas SF6 is not easily hydrolysed


(ii) Chlorine water is a powerful bleaching agent.


(iii) is a stronger oxidizing agent than Sb(V)


(b) What happens when


(i) White phosphorus is heated with concentrated NaOH solution in an inert atmosphere of CO2.


(ii) XeF6 undergoes partial hydrolysis.


(Give the chemical equations involved).


OR


(a) What inspired N. Bartlett for carrying out a reaction between Xe and PtF6?


(b) Arrange the following in the order of property indicated against each set:


(i) F2, I2, Br2, Cl2(increasing bond dissociation enthalpy)


(ii) NH3, AsH3, SbH3, BiH3, PH3(decreasing base strength)


(c) Complete the following equations:


(i)


(ii)