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Q.
Which of the following will not give a positive iodoform test?
JamiaJamia 2006
Solution:
Key Idea: Iodoform test is positive for compounds which have $ C{{H}_{3}}-\overset{\begin{smallmatrix} O \\ || \end{smallmatrix}}{\mathop{C}}\, $ group or $ 2{}^\circ $ alcohol group. (a) $ \underset{has\text{ }2{}^\circ \text{ }alcoholic\text{ }group}{\mathop{C{{H}_{3}}-C{{H}_{2}}-\underset{\begin{smallmatrix} | \\ OH \end{smallmatrix}}{\overset{\begin{smallmatrix} H \\ | \end{smallmatrix}}{\mathop{C}}}\,-C{{H}_{3}}}}\, $ (b) $ \underset{has\text{ }C{{H}_{3}}COC(-)\text{ }group}{\mathop{C{{H}_{3}}C{{H}_{2}}C{{H}_{2}}\overset{\begin{smallmatrix} O \\ |\,| \end{smallmatrix}}{\mathop{C}}\,C{{H}_{3}}}}\, $ (d) $ \underset{has\text{ }C{{H}_{3}}CO(-)\text{ }group}{\mathop{C{{H}_{3}}\overset{\begin{smallmatrix} O \\ |\,| \end{smallmatrix}}{\mathop{C}}\,{{C}_{6}}{{H}_{5}}}}\, $ $ \therefore $ compounds in choice (a), (b) and (d) give positive iodoform test. $ \underset{(c)}{\mathop{C{{H}_{3}}C{{H}_{2}}\overset{\begin{smallmatrix} O \\ |\,\,| \end{smallmatrix}}{\mathop{C}}\,C{{H}_{2}}C{{H}_{3}}}}\, $ $ \because $ This compound does not have $ C{{H}_{3}}CO(-) $ or $ 2{}^\circ $ alcoholic group. $ \therefore $ It does not give positive iodoform test.