ADDITIONAL QUESTIONS 2014 – 10 MARK

1. How is benzoic acid prepared from

(i) Toluene / Methyl benzene (ii) Phenyl cyanide (iii) Carbon dioxide?

a) By oxidation: Toluene / Methyl benzene is oxidised by acidified KMnO4 or Potassium dichromate or alkaline KMnO4 gives Benzoic acid.

                 H+ / KMnO4

C6H5CH3          →       C6H5COOH

b) Hydrolysis: Phenyl cyanide is hydrolysed with aqueous acid to give Benzoic acid.

                 H+                        H+

C6H5CN → C6H5CONH2 → C6H5COOH

                H2O  Benzamide  H2O

c) From Grignard reagent: Carbonation of C6H5MgBr followed by hydrolysis gives Benzoic acid.

Or CO2 reacts with C6H5MgBr followed by hydrolysis gives Benzoic acid.

2. Explain the reduction of Nitrobenzene in alkaline medium.

In alkaline medium, Nitro benzene on reduction forms the intermediate products nitrosobenzene (C6H5NO) and phenyl hydroxylamine (C6H5NHOH). These undergo bimolecular condensation reaction. According to the appropriate reducing agent in alkaline medium different products are obtained.

3. An organic compound (A) of molecular formula C₂H₆O liberates hydrogen with metallic sodium. Compound (A) on heating with conc.H₂SO₄ at 440 K gives an alkene (B). Compound (B) when oxidised by Bayer's reagent gives compound (C) of molecular formula C₂H₆O₂. Identify (A), (B) and (C) and explain the reactions.

ANSWER

(A) Ethyl alcohol

(B) Ethylene

(C) Ethylene glycol

4. The metal (A) is extracted from its sulphide ore. On treatment with dil. nitric acid metal A gives a compound (B), which is also known as Lunar Caustics. (C) on heating at 723 K gives compound (C) and O₂ Identify A, B and C and explain the reactions.

ANSWER

(A) Silver

(B) Silver nitrate (Lunar caustics)

(C) Silver Nitrite

5. Write a note on  i) HVZ - reaction ii) Decarboxylation iii) Kolbe's electrolytic reaction

i) HVZ – reaction (Hell-Volhard Zelinsky reaction):

Halogenation of Carboxylic acid with Halogen and Phosphorous trihalide.

Or Conversion of Carboxylic acid to α - bromo acid with Br2 / PBr3

                     Br2/PBr3                                                               H2O

RCH2COOH   →  RCH2COBr   →  RCHBrCOBr   →  RCHBrCOOH

ii) Decarboxylation:

 When anhydrous sodium salts of carboxylic acids are heated with soda lime, carboxyl group is removed with the formation of hydrocarbon containing one carbon atom less.

                         NaOH / CaO

RCOONa          →           RH + Na₂CO₃

                          ∆      (Hydrocarbon)

                        NaOH / CaO

CH3COONa          →            CH4 + Na₂CO₃

                                ∆         Methane

iii) Kolbe's electrolytic reaction:

Electrolysis of concentrated aqueous solution of Sodium salt of acids gives Hydrocarbon.

                            Electrolysis

CH3 – COO – Na      →     CH3 

          +                                |      + 2CO2   +  2Na

CH3 – COO – Na               CH3                    Sodium

                                           Ethane

6. Starting from benzene diazonium chloride how will you obtain the following i) Phenol, ii) Anisole, iii) p-hydroxy azobenzene?

i) When the aqueous solution of C6H5 N2 Cl is boiled, Phenol is obtained.

C6H5 N2 Cl → C6H5OH + N2 + HCl

    HO ––– H

ii) When C6H5 N2 Cl is warmed with alcohol, Anisole is formed.

C6H5 N2 Cl → C6H5O CH3 + N2 + HCl

CH3O ––– H

iii) Phenol couples with Benzene diazonium chloride in alkaline medium to form p-hydroxy azobenzene.

7. An organic compound (A) of molecular formula C₆H₆O gives violet colour with neutral FeCl₃. (A) reacting with CCl₄ and NaOH gives two isomers (B) and (C). (A) oxidation with CrO₂Cl₂ gives (D) of molecular formula C₆H₄O₂. Identify (A), (B), (C) and (D). Explain the reactions.

ANSWER	(A) Phenol	(B) o-Hydroxy benzoic acid / Salicylic acid
	(C) p-Hydroxy benzoic acid	(D) p – Benzoquinone

8. An organic compound (A) of molecular formula C₇H₆O, is called as oil of  bitter almonds. (A) oxidation gives (B) of molecular formula C₇H₆O₂ which gives brisk effervescence with NaHCO₃ solution. When (A) is refluxed with aqueous alcoholic KCN compound (C) is formed. . Identify (A), (B), (C) and (D). Explain the reactions.

ANSWER

(A) Benzaldehyde

(B) Benzoic acid

(C) Benzoin (Dimer of benzaldehyde)

9. An organic compound (A) of molecular formula C3H8O3 is obtained as by-product in the manufacture of soap. Compound (A) on heating with P2O5 gives an unsaturated compound (B) of molecular formula C3H4O. Compound (A) with well cooled mixture of conc. H2SO4 and fuming HNO3 form compound (C) which is yellow in colour. Identify A, B, C and D. Explain the reaction.

ANSWER

(A) Glycerol

(B) Acrolein

(C) Nitroglycerine or Glyceryl trinitrate

10. Compound ‘A’ is a powerful oxidizing agent and also it is a red orange crystal which melts at 396oC. ‘A’ reacts with chloride salt and Conc.H2SO4 to give ‘B’ which is reddish orange in colour. ‘A’ also reacts with KOH to give ‘C’ which is yellow in colour. Find out (A), (B) and (C). Explain the reactions.

ANSWER

(A) Potassium dichromate

(B) Chromylchloride

(C) Potassium chromate

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