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Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: Big_Joe on January 03, 2009, 01:10:36 PM

Title: Identifying an ester
Post by: Big_Joe on January 03, 2009, 01:10:36 PM

Is there a SIMPLE chemical test that can be done to identify if an unknown chemical is an ester?

I've heard of this but cant confirm if it is true:


Add NaOH and reflux.
Then add some 1M sulphuric acid, and if there's a precipitate, that identifies the presence of an ester.

Could someone confirm if this is true or not? If not then could someone please suggest an alternative way of identifying one, other than smell or spectroscopy.

Title: Re: Identifying an ester
Post by: Mr Peanut on January 03, 2009, 06:10:50 PM

The NaOH will hydrolyze the ester to an alcohol and the Na salt of the acid. The sulfuric acid will kickout the acid by protonaing it. The procedure assumes the acid itself is not soluble in water. Not always so.

A fair amount of material on a colorimetric test with hydroxylamine is out there.

Title: Re: Identifying an ester
Post by: CopperSmurf on January 17, 2009, 09:27:17 PM

Mr. Peanut is right.

There is one very old ancient test I know of to test for esters and ethers but I don't think it's allowed anymore because it needs mercury. It's called Zeisel's Test. It also needs concentrated HI and acetic acid.

Title: Re: Identifying an ester
Post by: ARGOS++ on January 18, 2009, 03:30:22 PM

Dear Big_Joe;  Dear faith_legend;

How about:   http://www.chemistry.ccsu.edu/glagovich/teaching/316/qualanal/tests/zeisel.html

Good Luck!
                    ARGOS⁺⁺

Title: Re: Identifying an ester
Post by: CopperSmurf on January 22, 2009, 05:27:02 PM

that's the one.