Intramolecular Hydrogen Bond Effects on Photodissociation of Hydroxybenzoic acids and Hydroxyacetophenone
Date Issued
2010
Date
2010
Author(s)
Yang, Yi-Lin
Abstract
Phenol is a chromophore of amino acid tyrosine. The photostability of amino acids is very important to life. According to the experimental results and theoretical calculations, phenol absorb an UV photon are excited to ππ* electronic excited state. The ππ* state couples with a πσ* repulsive state. Then the H atom of O-H bond eliminates from the repulsive state. The photodissociation produce the radicals which cause further reaction. That is opposite to the photostability of amino acids. To go a step further to study the effect of the different side chains on H elimination channel, 2-,3-,4-hydroxybenzoic acid and 2-,3-,4-hydroxyacetophenone are chosen in this experiment. We study the photodissociation of each compound by using multimass ion imaging technique. For hydroxybenzoic acid, H elimination is the major channel for 3-,4-hydroxybenzoic acid and H2O elimination is the major channel for 2-hydroxybenzoic acid. On the other hand, COCH3 elimination is the major channel for 2-, 3-, 4-hydroxyacetophenone. H elimination is observed for 3-, 4-hydroxyacetophenone but it is not observed for 2-hydroxyacetophenone. In comparison with photodissociation channels and molecular structures, H elimination from the repulsive excited state is quenched for the molecules
with intramolecular hydrogen bond.
Subjects
Photodissociation
Hydroxybenzoic acid
Hydroxyacetophenone
Intramolecular Hydrogen Bond
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