Abstract
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.
Highlights
Iourea derivatives and their transition metal complexes have been known since the beginning of the 20th century. e syntheses of the thiourea derivatives are with good yields [1]. iourea and its derivatives represent a wellknown important group of organic compounds due to the diverse application in elds such as medicine, agriculture, coordination, and analytical chemistry [2]. e benzoyl thiourea derivatives have a wide range of biological activities including antiviral [3], antibacterial [4,5,6], antifungal [7], antitubercular [8, 9], herbicidal [10], insecticidal [11], and pharmacological properties [12] and acting as chelating agents [13, 14]
On the continuation of our research on the determination of ionization constants of some industrial useful organic compounds in this study, we report the stoichiometric ionization constants of some substituted benzoyl thioureas in dioxane : water mixture (v : v, 50 : 50)
E benzoyl thiourea derivatives were prepared by a procedure similar to that reported in the literature [29, 30]. e benzoyl thiourea derivates were puri ed by recrystallization from ethanol : dichloromethane (1 : 2) mixture. e synthesized compounds were characterized by infrared spectroscopy, nuclear magnetic resonance, and elemental analysis
Summary
Iourea derivatives and their transition metal complexes have been known since the beginning of the 20th century. e syntheses of the thiourea derivatives are with good yields [1]. iourea and its derivatives represent a wellknown important group of organic compounds due to the diverse application in elds such as medicine, agriculture, coordination, and analytical chemistry [2]. e benzoyl thiourea derivatives have a wide range of biological activities including antiviral [3], antibacterial [4,5,6], antifungal [7], antitubercular [8, 9], herbicidal [10], insecticidal [11], and pharmacological properties [12] and acting as chelating agents [13, 14]. Iourea and its derivatives represent a wellknown important group of organic compounds due to the diverse application in elds such as medicine, agriculture, coordination, and analytical chemistry [2]. On the continuation of our research on the determination of ionization constants of some industrial useful organic compounds in this study, we report the stoichiometric ionization constants of some substituted benzoyl thioureas in dioxane : water mixture (v : v, 50 : 50). E stoichiometric ionization constants have been measured by the potentiometric titration, and calculations were performed by the BEST computer so ware [27, 28]. In this research, the effects of substituents and alkyl groups on the ionization constants of the benzoyl thiourea derivatives have been discussed
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