Substituent and Solvent Effects: Examining Acidity via Infrared Spectroscopy by Jordan Buhle

Substituent and Solvent Effects: Examining Acidity via Infrared Spectroscopy by Jordan Buhle

Chemistry

There is a large collection of substituent constant data measured in polar protic and polar aprotic solvents, but a lack of information on substituent effects in nonpolar aprotic solvents. In this study, substituent effects on the acidities of phenol derivatives were examined in CCl4 using infrared (IR) spectroscopy. The IR peak of the free phenolic -OH appears at approximately 3600 cm-1 which is red shifted in the presence of a hydrogen bond acceptor. The magnitude of the splitting between the free and the hydrogen-bonded -OH peak is related to the acidity of the protic hydrogen. Deuterated acetonitrile was used as the hydrogen-bond acceptor to probe the relative acidities of 21 phenol derivatives in CCl4. While most phenol derivatives exhibited similar acidity trends in CCl4 as in DMSO and the gas phase, several demonstrated a reduction in acidity which indicates a solvent dependence on substituent effects. This study offers a facile method to examine substituent effects on the acidity of alcohols and has identified several solvent-dependent substituent effects.

Buhle, Jordan

Senior Showcase Oral presentation

Ripon College

April 23, 2015

The author reserves all rights.

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Major: Chemistry
Minors: Spanish, Physics

Milton, Wisconsin

CHM 502 Chemistry Senior Seminar