Variation in phenolic Ka of parabens with varying ester group and their effect on the Hammett function

ORGN 569

John J. Sczepanski, John.Sczepanski@MontgomeryCollege.edu, Physical Sciences, Montgomery College, Takoma Park, Takoma Park, MD 20912 and Leopold May, MAY@CUA.EDU, Department of Chemistry, Catholic University of America, Washington, DC 20064.
We were investigating the biological activities of 4-hydroxy-benzoic acid esters (parabens) and found that the Ka varied with ester structure. Reviews of the Hammett equation indicate that sigma values do not vary when the alkyl substituent in ester group has more than three carbons. The variation of Ka suggested that the sigma values changes with the structure of the ester, contrary to the accepted views. However, the Kas were previously measured in ethanol. To verify the variation of the Kas and to eliminate solvent effects, we measured the Kas of parabens in an aqueous environment and observed significant variation of Kas. This will be discussed with relationship to the sigma values.
 

Asymmetric Reactions, Heterocycles, Aromatics, Combinatorial, and Physical Organic Chemistry
8:00 PM-10:00 PM, Wednesday, 31 August 2005 Washington DC Convention Center -- Hall A, Poster

Division of Organic Chemistry

The 230th ACS National Meeting, in Washington, DC, Aug 28-Sept 1, 2005