Q26 of 26 Page 1

(a) Write the reactions involved in the following :

(i) Hofmann bromamide degradation reaction


(ii) Diazotisation


(iii) Gabriel phthalamide synthesis


(b) Give reasons :


(i) (CH3)2NH is more basic than (CH3)3N in an aqueous solution.


(ii) Aromatic diazonium salts are more stable than aliphatic diazonium salts.


OR


(a) Write the structures of the main products of the following reactions:



(b) Give a simple chemical test to distinguish between Aniline and N,N-dimethylaniline.


(c) Arrange the following in the increasing order of their pKb value:


C6H5NH2, C2H5NH2, C6H5NHCH3

(a) (i)

When an amide is treated with bromine in an aqueous solution of sodium hydroxide, degradation of amide take place leading to the formation of primary amines.


R – CH2 – C(0) – NH2 + 4 NaOH + Br2 →R – CH2 – NH2 + Na2 CO3 + 2NaBr + 2H2O


(ii) Diazotisation


Aromatic primary amines react with nitrous acid at low temperatures to form diazonium salts. This conversion of aromatic primary amines into diazonium salts is nown as diazotization.



(iii) Gabriel phthalimide synthesis


Gabriel phthalimide synthesis is a very useful method for the preparation of aliphatic primary amines. It involves the reaction of phthalimide with ethanolic potassium hydroxide to form potassium salt of phthalimide. The product is further heated with alkyl halide, followed by alkaline hydrolysis to yield the corresponding amine.




(b) (i) (CH3)2NH is more basic than (CH3)3N in aqueos solutions because in(CH3)3N the lone pair of electrons on nitrogen atom is responsible forits basicity are quite hindered by the three methyl groups, hence are less available. Due to which it is less basic as compared to(CH3)2NH.


(ii)Aromatic diazonium salts are stable than aliphatic diazonium salts because the positive charge on nitrogen atom is stabilized by the resonance with attached phenyl group.


OR


(a)



(b) Aniline can be distinguished from N,N-dimethyl aniline


by diazo couping reaction. Anline would react with benzene diazonium chloride to give yellow dye, where as N,N-dimethyl aniline won’t undergo this reaction.



(c) C2H5NH2 < C6H5NH2 < C6H5NHCH3


Ethylamine is soluble in water whereas aniline is not so pKb aniline is higher than that of ethylamine


More from this chapter

All 26 →
22

(a) Write the formula of the following coordination compound : Iron(III) hexacyanoferrate (II)

(b) What type of isomerism is exhibited by the complex


(c) Write the hybridisation and number of unpaired electrons in the complex [CoF6 ]3- . (Atomic No. of Co = 27)

 23

Shyam went to a grocery shop to purchase some food items. The shopkeeper packed all the items in polythene bags and gave them to Shyam. But Shyam refused to accept the polythene bags and asked the shopkeeper to pack the items in paper bags. He informed the shopkeeper about the heavy penalty imposed by the government for using polythene bags. The shopkeeper promised that he would use paper bags in future in place of polythene bags.

Answer the following :


(a) Write the values (at least two) shown by Shyam.


(b) Write one structural difference between low-density polyethene and high-density polyethene.


(c) Why did Shyam refuse to accept the items in polythene bags ?


(d) What is a biodegradable polymer? Give one example?

 24

(a) Give reasons:


(i) H3PO3 undergoes disproportionation reaction, but H3PO4 does not.


(ii) When Cl2 reacts with an excess of F2. ClF3 is formed and not FCl3.


(iii) Dioxygen is a gas while Sulphur is a solid at room temperature.


(b) Draw the structures of the following:


(i) XeF4


(ii) HCLO3


OR


(a) When concentrated sulphuric acid was added to n unknown salt present in a test tube a brown gas(A) was evolved. This gas intensified when copper turning were added to this test tube . On cooling, the gas (A) changed int a colourless solid(B).


(i) Identify (A) and (B).


(ii) Write the structures of (A) and (B).


(iii) Why does gas (A) change to solid on cooling?


(b) Arrange the following in the decreasing order of theirreducing character:


HF, HCl, HBr, HI


(c) Complete the following reaction:


XeF4 +SbF5→

 25

(a) Write the cell reaction and calculate the e.m.f. of the following cell at 298 K.

Sn (s ) | Sn 2+ (0.004 M )|| H+(0.020 M ) | H 2 (g )(1bar)| Pt (s)


(Given: E0 Sn+2/Sn=-0.14V )


(b) Give reasons:


(i) On the basis of E0 values, O2 gas should be liberated at anode, but it is Cl2 gas which is liberated in the electrolysis of aqueous NaCl.


(ii) The conductivity of CH3COOH decreases on dilution.


OR


(a) For the reaction


2AgCl(s) + H2(g) (1 atm) → 2Ag(s) + 2H+ + 2H+ (0.1M) + 2Cl- (0.1M),


ΔG° = -43600J at 35° C.


Calculate the e.m.f. of the cell.


[log 10-n = -n]
(b) Define fuel cell and write its two advantages.