What changes would be seen on an INFRARED SPECTRA when ethanol is oxidised to ethanal?
Ethanal (CH3CHO)
Answer:
Ethanol: http://www.aist.go.jp/riodb/sdbs/cgi-bin...
Ethanal (also called acetylaldehyde):
http://www.aist.go.jp/riodb/sdbs/cgi-bin...
Strong carbonyl peak at ~1700 (1727 in the spectrum) in acetylaldehyde, lack of -OH peak.
The noticeable ones are that you would see a sharp peak at about 1700 from the aldehyde. And the absence of the large,broad, peak representing the alcohol.
Ethanol will exhibit a C-H stretch at ~2900cm-1, a OH will exhibit a broad stretch around 3300-3500cm-1.
When oxidized to ethanal the broad OH stretch will dissappear you will now see the C-H stretch shift to around 3000cm-1 due to its change from an sp3 to an sp2 hybridized carbon, you will see a stretch around 1700cm-1 due to the aldehyde and the ketone formed
The broad O-H stretch at 3300cm-1 of the alcohol would disappear and the C=O stretch of the aldehyde at 1700cm-1 would appear.
Incidentally if you oxidised it further to the carboxylic acid the O-H stretch at 3300cm-1 would reappear.
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