Question

Which of the following will not give a positive iodoform test?

• A. $C{H}_{3}C{H}_{2}CHOHC{H}_3$
• B. $C{H}_{3}C{H}_{2}C{H}_{2}COC{H}_3$
• C. $C{H}_{3}C{H}_{2}COC{H}_{2}C{H}_3$
• D. $C{H}_{3}CO{C}_6{H}_5$

Answer 1

Answer: (C)

Key Idea: Iodoform test is positive for compounds which have $C{H}_3-\stackrel{\begin{array}{c}O\\ ||\end{array}}{C}$ group or $2{}^{\circ }$ alcohol group. (a) $\underset{has2{}^{\circ }alcoholicgroup}{C{H}_3-C{H}_2-\underset{\begin{array}{c}|\\ OH\end{array}}{\stackrel{\begin{array}{c}H\\ |\end{array}}{C}}-C{H}_3}$ (b) $\underset{hasC{H}_{3}COC(-)group}{C{H}_{3}C{H}_{2}C{H}_2\stackrel{\begin{array}{c}O\\ ||\end{array}}{C}C{H}_3}$ (d) $\underset{hasC{H}_{3}CO(-)group}{C{H}_3\stackrel{\begin{array}{c}O\\ ||\end{array}}{C}{C}_6{H}_5}$ $\therefore$ compounds in choice (a), (b) and (d) give positive iodoform test. $\underset{(c)}{C{H}_{3}C{H}_2\stackrel{\begin{array}{c}O\\ ||\end{array}}{C}C{H}_{2}C{H}_3}$ $\because$ This compound does not have $C{H}_{3}CO(-)$ or $2{}^{\circ }$ alcoholic group. $\therefore$ It does not give positive iodoform test.