How will you distinguish between methanol and ethanol?
Correct answer: D. By Iodoform test
- A. By Lucas test
- B. By silver mirror test
- C. By oxidation
- D. By Iodoform test
Explanation
The solution in the ethanol test tube should go cloudy and then a yellow precipitate of tri-iodomethane (iodoform) should be seen. Methanol won't react.The iodoform test is a specific test for methyl ketones, including acetone. Methanol does not react with the iodoform test. However, ethanol can undergo oxidation to acetaldehyde, which is a methyl ketone, and subsequently react with iodine and sodium hydroxide (NaOH) to produce a yellow precipitate of iodoform. This test can help differentiate between ethanol and methanol.
This question appeared on the UHS MDCAT 2015 paper, which you can sit online with every answer explained.
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About Alcohols
Alcohols contain a hydroxyl group attached to a saturated carbon atom and are classified as primary, secondary or tertiary. Their nomenclature, hydrogen bonding, acidity, oxidation, dehydration, reaction with sodium and conversion to haloalkanes are covered, along with the distinction between alcohols and phenols, where the hydroxyl group is attached directly to an aromatic ring.
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