An Easy and Versatile Experiment to Demonstrate Solvent Polarity Using Solvatochromic Dyes

Vanderlei Gageiro Machado
Departamento de Química, Universidade Federal do Paraná, UFPR, CP 19081, Curitiba, PR 81531-990, Brazil
Clodoaldo Machado
Departamento de Química, Universidade Regional de Blumenau, FURB, CP 1507, Blumenau, SC 89010-971, Brazil
J. Chem. Educ., 2001, 78 (5), p 649
DOI: 10.1021/ed078p649
Publication Date (Web): May 1, 2001

Abstract

In this easy and versatile experiment, undergraduate students of experimental physical chemistry can discuss the concept of media polarity on the basis of the solvatochromic approach. Two solvatochromic dyes, Reichardt's betaine 2,6-diphenyl-4-(2,4,6-triphenyl-1-pyridinio)-1-phenoxide and Brooker's merocyanine 4-[(1-methyl-4(1H)-pyridinylidene)ethylidene]-2,5-cyclohexadien-1-one were used to construct polarity scales for various solvents by means of visual observation and UV-vis spectroscopy. Changes in media polarity arising from mixed solvents or added electrolytes are also easily demonstrated. The data are used to justify kinetic and spectroscopic parameters.

Keywords (Audience):

Upper-Division Undergraduate

Keywords (Domain):

Demonstrations

Keywords (Pedagogy):

Hands-On Learning / Manipulatives

Keywords (Subject):

Solutions / Solvents

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  • Received: August 03, 2009

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