Medium and structural effects on the ionization constants of some pyrazole carboxylic acid derivatives

Alkan, Sibel; Zeybek, Bülent; Doğan, Alev; Kasımoğulları, Rahmi; Erdoğan, Yunus; Kılıç, Esma

doi:10.1007/s00706-008-0037-y

Cited by 2 publications

(1 citation statement)

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“…It was therefore concluded that the electrode could be used to determine the potentiometric constants for 50% dioxane-50% water (v : v) media. e electrode which exhibited Nernstian behavior in acidic media was found to show the same behavior in alkaline media [38].…”

Section: Resultsmentioning

confidence: 82%

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

Binzet

Zeybek

Kılıç

et al. 2012

Journal of Chemistry

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The stoichiometric ionization constants ofN,N-dialkyl-N′-(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 and25.0±0.1°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, andn-butyl thiourea derivatives(−C2H5<−C3H7<−C4H9)shows that then-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 ofpKavalues 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<4-Cl<4-H) can be explained by considering the total electronic substituent effect (electron-withdrawing and electron-donating effects) except the 4-Br_Ph derivative.

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Section: Resultsmentioning

confidence: 82%