Raman Spectra Studies

In Raman spectra, the peaks at 1730 cm"1 for COOH and at 3320 cm-1 for NH2 are not found in amino acids, but a peak atl400 cm-1 for COO" is detected. In the amino acid hydrochloride salt, a peak of 1730 cm-1 for COOH is detected, but the peak for NH3 is not detected because of the overlap with the absorbency of water.

The unionized COOH group frequency near 1730 cm-1 is a particular feature of the spectra. This COOH group would be expected to be present in all relatively unionized carboxylic acids, and if the dipolar ion character of the amino acids is true, this group would also be expected to occur in the hydrochlorides of the amino acids. When the carboxyl group is ionized, the 1730-cm"1 line disappears, thus further suggesting the dipolar ion character of the amino acids under these conditions (26-31). RCOOH or NH3+RCOOH + CI" shows a 1730-cm"1 line, butRCOO" or NH3 COO" does not show a 1730-cm"1 line.

Vegetarian Food and Cooking

Vegetarian Food and Cooking

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