you heated EPA with some inorganic material to do what? you know the carbonyl group affected by many factors that connected with it. so different values may be observed lower or higher than original value . try to explain your question in more details.

When the carbonyl group is CONJUGATED with a double bond or a ring, i.e. there is the arrangement -C=C-C=O, conjugation shifts the IR absorbance to the right by about 30 cm-1.

See the attached which is part of a typical table which you & I consult for IR spectra interpretation.

Makhdoom,

You wrote

"It is said that unsaturated esters have low wavelength values (1715-1730 cm-1) at FTIR spectra than saturated esters (1735-1750 cm-1). I have heated ethylphenylacetate with some inorganic materials but FTIR peak of carbonyl group of this unsaturated ester become at 750, which is higher. Can anyone explain the reason ?"

Do you mean ethyl phenylacetate or alkyl(aryl) ethylphenylacetate?

Heating your molecule with inorganic materials !!! Did you work up the reaction mixture and isolated a pure material for which you obtained an IR? You are saying "carbonyl group of this unsaturated ester become at 750" Do you mean 1750 cm-1 !!! and how did you come up with saying unsaturated ester !!!?

Have you obtained 1H-NMR for your pure product?

If you really need assistance clarify your question.

Good luck

Makhdoom,

Please note that unsaturated carbonyl means C=C-C=O system as mentioned by Dr. Nizar. In your case phenyl group and the ester group are isolated by CH2 group. Are you taking the IR in the gas phase? Do you obtain IR for pure compound or the reaction mixture?

At the moment you may look at

---http://books.google.com.sa/books?id=lg2r9BDlbM8C&pg=PA586&lpg=PA586&dq=ethyl+phenylacetate+pyrolysis&source=bl&ots=RZ5o8TsQVS&sig=crfEzdOlxYgNzz2ROSJLMI63xKo&hl=en&sa=X&ei=NxyKU-bRCoTfOKqCgfAM&ved=0CDAQ6AEwAg#v=onepage&q=ethyl%20phenylacetate%20pyrolysis&f=false

Good luck

Makhdoom,

Well, it seems that you have further decomposition to carbon monoxide which coordinate with the metal forming metal-carbonyl. The frequency 1750 cm-1 matches well with this group. Just think about it !!!

Good luck