Protonation acidity constants for benzotoluidides in sulfuric acid solutions

• Authors: Goran Stojković , Frosa Anastasova
• Languages of publication: EN

Abstracts

EN

The protonation of o-, m-and p-benzotoluidide in sulfuric acid solutions is studied by UV spectroscopy in the 190–350 nm region. Principal component analysis is applied to estimate the contributions of the effect of protonation and the medium effect. For the substances studied in this work, the first principal component (PC) captures about 98 % of the variance and the second PC ∼100 % of the cumulative percentage variance in the 210–350 nm region. The same spectral region is used for calculation of the ionization ratio from the coefficients of the first PC and mole fractions of the base and its conjugate acid. Using these data and Hammett's equation (pK
BH
+ = H
X + log I), the pK
BH
+ values for the protonation reaction are obtained. The dissociation constants as well as the solvent parameters m* (∼0.43) and ϕ (∼0.60) are calculated using the Excess Acidity Method (-pK
BH
+= 2.28–2.30) and the Bunnett-Olsen Method (-pK
BH
+= 2.24–2.28). The probable sites of protonation are discussed.

Keywords

EN

Benzotoluidides; protonation; dissociation constants; spectrophotometry

• Publisher: De Gruyter Open
• Journal: Open Chemistry
• Year: 2006
• Volume: 4
• Issue: 1
• Pages: 56-67

Dates

published

1 - 3 - 2006

online

1 - 3 - 2006

Contributors

author

Goran Stojković

• Institute of Chemistry, Faculty of Natural Sciences and Mathematics, Sts. Cyril & Methodius University, 1001, Skopje, Republic of Macedonia

author

Frosa Anastasova

• Institute of Chemistry, Faculty of Natural Sciences and Mathematics, Sts. Cyril & Methodius University, 1001, Skopje, Republic of Macedonia

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Identifiers

DOI

10.1007/s11532-005-0004-y