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Journal of Chemistry
Volume 2013, Article ID 201238, 7 pages
http://dx.doi.org/10.1155/2013/201238
Research Article

Determination of the Ionization Constants of Some Benzoyl Thiourea Derivatives in Dioxane-Water Mixture

1Department of Chemistry, Faculty of Education, Mersin University, 33343-Mersin, Turkey
2Department of Chemistry, Faculty of Arts and Sciences, Dumlupınar University, 43000-Kütahya, Turkey
3Department of Chemistry, Faculty of Sciences, Ankara University, 06100-Ankara, Turkey
4Department of Chemistry, Faculty of Arts and Science, Mersin University, 33343-Mersin, Turkey

Received 26 June 2012; Accepted 29 August 2012

Academic Editor: Josefina Pons

Copyright © 2013 Gun Binzet et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The stoichiometric ionization constants of N,N-dialkyl- -(4-substituted benzoyl) thiourea (Substitutes: H, Cl, and Br; alkyl groups: ethyl, n-propyl, n-butyl, and phenyl) derivatives have been determined potentiometrically in dioxane-water (v:v, 50:50) mixture at ionic strength of 0.1 M and °C. The ionization constants were calculated with the BEST computer program and the formation curves using the data obtained from the potentiometric titrations. The effects of substituents and alkyl groups on the ionization constants of the benzoyl thiourea derivatives have been investigated. A comparison of the basicities of ethyl, n-propyl, and n-butyl thiourea derivatives shows that the n-butyl group is a more powerful electron-releasing group than the other groups in 50% dioxane-50% water mixture (v:v). So, the acidity of benzoyl thiourea derivative compounds decreases, while the length of alkyl chain increases. The orders of values for all thiourea derivatives are as expected in the light of steric, resonance and inductive effects of substituents. Furthermore, when the basicities of halogen derivatives of the same substitution pattern are compared, orders obtained (4-Br -Cl -H) can be explained by considering the total electronic substituent effect (electron-withdrawing and electron-donating effects) except the 4-Br_Ph derivative.