CET Karnataka Engineering CET - Karnataka Engineering Solved Paper-2004

  • question_answer
    The reagent which does not give acid chloride on treating with a carboxylic acid is :

    A)  \[PC{{l}_{5}}\]                 

    B)  \[C{{l}_{2}}\]

    C)  \[SOC{{l}_{2}}\]                              

    D)  \[PC{{l}_{3}}\]

    Correct Answer: B

    Solution :

    \[PC{{l}_{3}},\,PC{{l}_{5}}\] and \[SOC{{l}_{2}}\] are used to replace \[-OH\] group of an alcohol or an acid by \[-Cl\]group \[R-\overset{\begin{smallmatrix}  O \\  || \end{smallmatrix}}{\mathop{C}}\,-OH+PC{{l}_{5}}\xrightarrow{{}}R-\overset{\begin{smallmatrix}  O \\  || \end{smallmatrix}}{\mathop{C}}\,-Cl\]                                                 \[+\,POC{{l}_{3}}+HCl\] \[R-\overset{\begin{smallmatrix}  O \\  || \end{smallmatrix}}{\mathop{C}}\,-OH+SOC{{l}_{2}}\to R-\overset{\begin{smallmatrix}  O \\  || \end{smallmatrix}}{\mathop{C}}\,-Cl\]                                                                 \[+\,S{{O}_{2}}+HCl\] when acid reacts with \[C{{l}_{2}}\] in presence of red phosphorus, \[\alpha \]-chloroacid is obtained. (Hall-Vohlard Zelinsky reaction). \[C{{H}_{3}}C{{H}_{2}}COOH+C{{l}_{2}}\xrightarrow[\Delta ]{red\,\,S}\]                                 \[\underset{\alpha -chloropropionic\text{ }add}{\mathop{C{{H}_{3}}\overset{\begin{smallmatrix}  Cl \\  | \end{smallmatrix}}{\mathop{C}}\,HCOOH+HCl}}\,\]


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