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Aldehydes, Ketones, and Carboxylic Acids — Chemistry STD 12 Science — Question

Gujarat BoardEnglish MediumSTD 12 ScienceChemistryAldehydes, Ketones, and Carboxylic Acids2 Marks
Question
Write the reactions involved in the following :
  1. Hell-Volhard Zelinsky reaction
  2. Decarboxylation reaction
✓

Answer

  1. Hell-Volhard Zelinsky reaction: Carboxylic acid having α-hydrogen are halogenated at α- position on treatment with chlorine or bromine in the presence of red phosphorous to give α-halogenated carboxylic acid.
$\text{HVZ reaction}\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\\\text{RCH}_2\text{COOH}\xrightarrow[\text{(ii) H}_2\text{O}]{\text{(i) X}_2/\text{Red P}}\text{RCHCOOH}\\\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }|\\\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{X}$
  1. Decarboxylation reaction: Carboxylic acid lose $CO_2$ to form hydrocarbons when their sodium salts are heated with sodalime $(NaOH$ and $CaO$ in the ratio $3:1).$ The reaction is known as decarboxylation reaction.
$\text{RCOONa}\xrightarrow[\triangle]{\text{NaOH and CaO}}\text{RH}+\text{Na}_2\text{CO}_3$

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