Spectroscopic Studies And Kinetics Of Cyclisation Of N-Carbobezoxy-L–Amino Acids With Ethanoic-Anhydride.

ABSTRACT

The spectroscopic and kinetics of cyclisation of Ncarbobenzoxy-
L-a-amino acid derivatives to form their
oxazol-5(4H)-ones were studied. The absorption maxima of
the amino acid derivatives were found to be affected by the
polarities of various solvents employed. Polar solvents
shifted the max to longer wavelengths. The shifts have been
attributed to either
n —> or transitions respectively.
The cyclisation rates of N-carbobenzoxy-L-a-amino
acids studied were found to be influenced by the nature and
size of the alkyl groups at the a-carbon as well as the
substituent group at the nitrogen atom. The rate constants
were affected by the size of the alkyl groups. The rate
constants obtained from the linear plots of time versus
logarithm of absorbances of each of the amino acids were
used to correlate the linear free energy relationships using
the Taft-equations. The steric and polar factor
contributions were found to greatly influence the
cyclisation rates.