Q36 of 37 Page 1

An organic compound A with molecular formula C7H7NO reacts with Br2/aq. KOH to give compound B, which upon reaction with NaNO2 & HCl at 0°C gives C. Compound C on heating with CH3CH2OH gives a hydrocarbon D. Compound B on further reaction with Br2 water gives white precipitate of compound E. Identify the compound A, B, C, D & E; also justify your answer by giving relevant chemical equations.

OR


(a) How will you convert:


(i) Aniline into Fluorobenzene.


(ii) Benzamide into Benzylamine.


(iii) Ethanamine to N,N-Diethylethanamine.


(b)Write the structures of A and B in the following:


(i)


(ii)


The given compound A is C6H5CONH2, an amide which undergoes Hoffmann Bromamide synthesis which gives the compound B, primary amine C6H5NH2 aniline. Aniline reacts with NaNO2 and HCl at 0°C to give compound C Benzene Diazonium Chloride, a diazo salt. Benzene diazonium chloride reacts with ethanol, CH3CH2OH to give a compound D hydrocarbon Benzene by elimination of N2+Cl- and replacement with H. The given compound B is aniline because only aniline reacts with Br2 water to give a white precipitate of compound E, 2,4,6-tribromophenylamine.

The reactions are as follows.






2,4,6-tribromophenylamine


OR


a(i) Aniline is treated with NaNO2 and HCl at 0°C to form benzene diazonium chloride. This salt on treatment with HBF4 or Fluroboric acid gives Fluorobenzene and has toxic gas BF3 as by-product.




(ii)Benzamide is converted to Benzylamine by Hoffmann bromamide synthesis, where an amide is treated with Br2 water and aqueous or ethanolic NaOH to give benzylamine, a primary amine.



(iii)Ethanamine, which is a primary amine, can be converted to N,N-Diethylethanamine which is a tertiary amine by ammonolysis of alkyl halides. An alkyl or benzyl halide on reaction with an ethanolic solution of ammonia undergoes nucleophilic substitution reaction in which the halogen atom is replaced by an amino (–NH2) group. The reaction is carried out in a sealed tube at 100C. The primary amine thus obtained behaves as a nucleophile and can further react with alkyl halide to form secondary and tertiary amines, and finally quaternary ammonium salt. Ethanamine, C2H5—NH2, the primary amine is further treated with ethyl halide, C2H5X, leading to the substitution of the –H groups on ethanamine with the ethyl groups on the halide, first forming secondary amine N-ethylethanamine (C2H5)2NH, and then tertiary amine N, N-Diethylethanamine (C2H5)3N.


C2H5—NH2 + C2H5X → (C2H5)2NH + C2H5X → (C2H5)3N


(b)(i) CH3CH2CN, ethyl nitrile, on partial hydrolysis with mild heat with NaOH or KOH gives compound A, ethyl amide, CH3CH2CONH2.


CH3CH2CN + NaOH/KOH → CH3CONH2


Ethyl amide on treatment with NaOH and Br2 water undergoes Hoffmann Bromamide degradation to form compound B, a primary amine, ethyl amine, or CH3CH2NH2.


CH3CONH2 + Br2 + NaOH → CH3CH2NH2.


(ii) CH3CH2Br, ethyl bromide, when treated with KCN, undergoes nucleophilic substitution reaction to form CH3CH2CN. CH3CH2CN on treatment with LiAlH4, a strong reducing agent, forms compound A, CH3CH2NH2, ethyl amine, primary amine. CH3CH2NH2 on treatment with nitrous acid at 0C, forms compound B which is a diazo salt, ethyldiazonium ion or ethyldiazonium chloride, CH3CH2N2+Cl-


More from this chapter

All 37 →
33

(a) Give chemical tests to distinguish between the following pairs of compounds:

(i) Ethanal and Propanone.


(ii) Pentan-2-one and Pentan-3-one.(b) Arrange the following compounds in increasing order of their acid strength: Benzoic acid, 4- Nitrobenzoic acid, 3,4-Dinitrobenzoic acid, 4- Methoxybenzoic acid.


OR


Compare the reactivity of benzaldehyde and ethanal towards nucleophilic addition reactions. Write the cross aldol condensation product between benzaldehyde and ethanal.


 34

Define and write an example for the following:

(a) Broad-spectrum antibiotics.


(b) Analgesics


 35

(a) The e.m.f. of the following cell at 298 K is 0.1745 V

Fe (s) / Fe2+(0.1 M)//H+(xM)/ H2 (g) (1 bar)/ Pt (s)


Given:


= -0.44V


Calculate the H+ ions concentration of the solution at the electrode where hydrogen is being produced.


(b)Aqueous solution of copper sulphate and silver nitrate are electrolysed by 1 ampere current for 10 minutes in separate electrolytic cells. Will the mass of copper and silver deposited on the cathode be same or different? Explain your answer.


OR


(a) Calculate the degree of dissociation of 0.0024 M acetic acid if conductivity of this solution is 8.0 × 10-5 S cm-1.


Given: = 349.6 S cm2 mol-1; = 40.9 S cm2 mol-1


(b) Solutions of two electrolytes ‘A’ and ‘B’ are diluted. The limiting molar conductivity of ‘B’ increases to a smaller extent while that of ‘A’ increases to a much larger extent comparatively. Which of the two is a strong electrolyte? Justify your answer.


 37

(a) When a chromite ore (A) is fused with an aqueous solution of sodium carbonate in free excess of air, a yellow solution of compound (B) is obtained. This solution is filtered and acidified with sulphuric acid to form compound (C). Compound (C) on treatment with solution of KCl gives orange crystals of compound (D). Write the chemical formulae of compounds A to D.

(b) Describe the cause of the following variations with respect to lanthanoids and actinoids:


(i) Greater range of oxidation states of actinoids as compared to lanthanoids.


(ii) Greater actinoid contraction as compared to lanthanoid contraction.


(iii) Lower ionisation enthalpy of early actinoids as compared to the early lanthanoids.


OR


(a) What happens when:


(i) Manganate ions (MnO42-) undergoes disproportionation reaction in acidic medium?


(ii) Lanthanum is heated with Sulphur?


(b) Explain the following trends in the properties of the members of the First series of transition elements:


(i) E0(M2+|M) value for copper is positive(+0.34 V) in contrast to the other members of the series.


(ii) Cr2+ is reducing while Mn3+ is oxidising, though both have d4 configuration.


(iii) The oxidising power in the series increases in the order


VO2+< Cr2O72-< MnO4-.