iodoform test: reaction with or KI solution?

Question

place about 5 drops of ethanol ina test tube, then add 1ml of water. add about 5 drops of KI solution. add 10% NaOH solution drop wise with shaking until the iodine color disappers and the solution if faintly yellow. examine the contents of the tube and note the color. what the rsult?

Answer 1

Lancenigo di Villorba (TV), Italy

I AGREE NOT WITH PREVIOUS ANSWERER.
You fell in CLASSICAL MISTAKES about Iodoform test.

ABOUT IODOFORM TEST)
Iodoform test can distinguish among Ketones on the basis of their molecular structures. Remarks are positives if you may see a yellowish body or Iodoform.
Generally, I said that METHYL-KETONES may react forming a Iodoform, other ketones do not.
Moreover, Acetaldehyde and Ethanol are the other stuffs able to react in this way.
You may built the Reacting Mixture starting from an alkaline aqueous medium, hence you add it with some drops of iodine solutions (e.g. Lugol's stuff). Now, you see the Reacting Mixture and you will note a clear liquid coloured as yellow-piss.
YOU HAVE NOT TILL ADDED THE STUFF!
Iodine dissolve it in alkaline medium decolouring itself

I2 + 2 OH- <---> I- + IO- + H2O

since the chemical EQUILIBRIUM PRESERVES A SMALL AMOUNT OF FREE IODINE WHICH IS VISIBLE AGAIN : the latter forms the yellowish coloration of the clear mixture.
Then, you add some drops of analyte and you must warm the mixture, so executing the test.
YOU MUST EXECUTE THE TEST IN WARM CONDITIONS, HENCE YOU MUST SEARCH A YELLOWISH SOLID. Viceversa, ETHANOL's TRACES lead you in mistakes!!

I hope this helps you.

Answer 2

The faint yellow-coloured solid, and a smell of antiseptic, confirms that ethanol gave a positive result.

This shows that ethanol contains the CH3CO group.