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The Chemical Educator

ISSN: 1430-4171 (electronic version)

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Abstract Volume 8 Issue 1 (2003) pp 56-59

Determination of the Acid Dissociation Constant of Fluorescein and Its Derivatives through Visible Absorption Techniques

Timothy R. Brewer* and Mace R. Mattieson

Chemistry Department, Eastern Michigan University, Ypsilanti, MI 48197,
Received May 7, 2002. Accepted August 5, 2002

Published online: 21 November 2002

Abstract. A discovery-based chemistry laboratory is presented that investigates the effects of electronegative substituents on the acid dissociation constants of fluorescein derivatives. The acid dissociation constants were measured through visible absorbance changes of the compounds at various pH values. The effect of electron-withdrawing constituents, such as chloro- and bromo-substituted fluorescein, is to lower the pKa value relative to the parent fluorescent molecule. Molecular modeling using Hartree–Fock calculations was used to qualitatively support the experimental results.

Key Words:  Laboratories and Demonstrations; physical chemistry; instrumental analysis; computational chemistry

(*) Corresponding author. (E-mail:

Article in PDF format (281 KB) HTML format

Supporting Materials:

A laboratory handout for students is available as supporting material. (Zip file 112 KB) 10.1007/s00897000624a

Issue date: February 1, 2003

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