Chemistry Alcohols & Phenols MDCAT 2016
PMDC Verified Question 81 of 95
Which one of the following is an appropriate indication of positive iodoform test?
A
Formation of \(\text{H}_2\text{O}\)
B
Brick red precipitate
C
Release of \(\text{H}_2\text{gas}\)
D
Yellow crystal
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option D: Yellow crystal
Concept:

Chemical qualitative tests rely on visual cues (color changes, gas evolution, precipitates) to confirm a reaction.

Formula:

$$ \text{CHI}_3 \text{ (Iodoform)} $$

Solution:

  • The final organic product of the haloform reaction utilizing iodine is triiodomethane (iodoform).


  • Iodoform is highly insoluble in aqueous solution and visually manifests as distinct pale yellow crystals with a medicinal smell.


Why other options are incorrect:

A brick red precipitate is characteristic of Fehling's or Benedict's test (due to \(\text{Cu}_2\text{O}\)). Hydrogen gas release is characteristic of metals reacting with acids or alcohols. Water formation is invisible.

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