Iodoform Test Ambiguity

• hoay

  1 Jul 11, 18:26

  The iodoform test is given by compounds having the CH3-CO or CH3-CH(CH3).

  What about the following molecules:

  CH3COCl

  CH3COOH

  CH3COOCH3

   

• donkhead333

  1 Jul 11, 18:57

  Negative for all. It's positive solely for aldehydes/ketones only. Acyl chlorides, carboxylic acids are exempt. Acyl chlorides hydrolyse in aqueous solution anyway..so negative.

• hoay

  1 Jul 11, 21:05

  all these groups contain the CH3-C=O group so they should give iodoform test!!

• SBS n SMRT

  1 Jul 11, 21:32

  It is for methylcarbonyls and methylalcohols only :)

  (CH3)CH(OH) - 

  (CH3)CO-

  Carbonyls cannot be in acid or acid derivatives as it's properties are affected by the OH group nearby

• UltimaOnline

  2 Jul 11, 00:51

  Donkhead333 and SBS n SMRT are correct. Iodoform reaction only works on methyl aldehydes, methyl ketones and methyl alcohols (which are actually automatically oxidized to methyl aldehydes / ketones first, before the iodoform reaction occurs).
  
  The reason why the iodoform reaction as well as the 2,4-DNPH reaction works only only aldehydes & ketones, but not carboxylic acids, esters or amides, is that the latter group are resonance stabilized and are therefore less reactive (remember : the more stable you are, the less reactive you are) than the former group. The iodoform and 2,4-DNPH test requires a level of reactivity that only the former, but not the latter group of compounds, meet.