Question

$PhCOC{H}_2,C{H}_2=CH-CHO,C{H}_{3}CH\left(OH\right)C{H}_{2}CH\left(OH\right)C{H}_3,IC{H}_{2}COC{H}_3,$

$C{H}_{3}CON{H}_2,C{H}_{3}COC{H}_{2}COC{H}_3,$ ref. image.

Find the total number of compounds which will not give yellow precipitate of iodoform when heated with $I_2$ and alkali?

• A. 1
• B. 2
• C. 3
• D. All will give

Answer 1

The correct option is C 3

$1)PhCOC{H}_2$ $2)C{H}_2=CH-CHO$ 3) ref. image

The total number of compounds which will not give yellow precipitate of iodoform when heated with iodine and alkali is 3.
If a compound contains a methyl keto group ($C{H}_{3}CO$) or a group that can be easily oxidized to methyl keto group, then it will give yellow precipitate of iodoform when heated with iodine and alkali.
If such a group is absent, then no ppt will be obtained.
Following three compounds do not contain methyl keto group. Hence, they will not give yellow precipitate of iodoform when heated with iodine and alkali