Q10 of 37 Page 1

Write the reactions involved in the following:

(i) Hell-Volhard Zelinsky reaction


(ii) Decarboxylation reaction

(i) Carboxylic acids having an α-hydrogen are halogenated at the α-position on reaction with chlorine or bromine in the presence of small amount of red phosphorus to give α-halocarboxylic acids. The reaction is known as Hell-Volhard-Zelinsky reaction. α hydrogen is the hydrogen attached to carbon which is immediately next to or attached to carbon of –COOH group of carboxylic acids.


R – CH2 – COOH R – CHX- COOH (α- halocarboxylic acid)


X = halogen


(ii) Sodium salts of carboxylic acids lose carbon dioxide to form hydrocarbons when they are heated with soda lime (NaOH and CaO in the ratio of 3 : 1) The reaction is known as decarboxylation. Sodium salts of carboxylic acids are the ones in which H of –COOH group is replaced by Na (-COONa)


R – COONa R- H + Na2CO3


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A. Write the product(s) in the following reactions:

(i)


(ii)


(iii)


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(i) Ethanol and Phenol


(ii) Propanol and 2-methylpropan-2-ol


OR


(a) Write the formula of reagents used in the following reactions :


(i) Bromination of phenol to 2,4,6-tribromophenol


(ii) Hydroboration of propene and then oxidation to propanol.


(b) Arrange the following compound groups in the increasing order of their property indicated :


(i) p-nitrophenol, ethanol, phenol (acidic character)


(ii) Propanol, Propane, Propanal (boiling point)


(c) Write the mechanism (using curved arrow notation) of the following reaction :


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(ii) zone refining


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