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Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: Aldebaran on May 29, 2022, 06:41:49 AM

Title: Distinguishing ketone from tertiary alcohol
Post by: Aldebaran on May 29, 2022, 06:41:49 AM
Other than using 2,4-DNPH (orange ppt. with ketone) I am trying to think of another simple test to differentiate a ketone from tertiary alcohol. A quick Google didn't produce anything. Any helpful suggestions?
Many thanks.
Title: Re: Distinguishing ketone from tertiary alcohol
Post by: sharbeldam on May 29, 2022, 08:35:09 AM
if its methyl ketone its haloform reaction.
otherwise, maybe lucas reagent
Title: Re: Distinguishing ketone from tertiary alcohol
Post by: Aldebaran on May 29, 2022, 11:51:51 AM
The question actually originated from considering linalool and ionone but got me thinking about the more general case and other options than 2,4-DNPH. Your suggestions are very helpful. I had thought about the Lucas reaction although I've never actually tried it out I am ashamed to admit!

Thanks.
Title: Re: Distinguishing ketone from tertiary alcohol
Post by: rolnor on May 30, 2022, 08:28:14 AM
Whats wrong with DNPH?
Title: Re: Distinguishing ketone from tertiary alcohol
Post by: Aldebaran on May 30, 2022, 02:09:47 PM
Nothing wrong with DNPH but one of my students asked if there were other tests and it got me thinking if there were other tests of general application.
Title: Re: Distinguishing ketone from tertiary alcohol
Post by: hollytara on June 01, 2022, 02:14:35 AM
There are other compounds that make derivatives like DNPH - hydroxylamine to make the oxime for example. 

If you want something for the alcohol, ceric ammonium nitrate.
Title: Re: Distinguishing ketone from tertiary alcohol
Post by: Humr on June 02, 2022, 02:34:43 PM
What about NaHSO3? It is used for purification of aldehydes or ketones. It forms crystals with those carbonyl compounds. Alcohol would not react.
Title: Re: Distinguishing ketone from tertiary alcohol
Post by: Meter on June 03, 2022, 06:42:51 AM
Maybe not simple, but if the ketone and alcohol are the only functional groups present in the respective compounds, a Grignard reagent will react differently with both. Also, not sure, but maybe you can use HX acids, since these react with alcohols to form alkyl bromides + water, which would affect the overall pH. In a solution with a ketone, I doubt much would happen.