Half-neutralization Potential Research Articles

Synthesis and determination of pKa values of some new di-{2-ethoxy-6-[(3-substitue-4,5-dihydro-1H-1,2,4-triazol-5-one-4-yl)azomethine]phenyl} terephthalates

In this study, seven novel di-{2-ethoxy-6-[(3-substitue-4,5-dihydro-1H-1,2,4-triazol-5-one-4-yl)azomethine]phenyl} terephtalates (4a-g) were synthesized from the rections of 3-alkyl(aryl)-4-amino-4,5-dihydro-1H-1,2,4-triazol-5-ones (2a-g) with di-(2-formyl-6-ethoxyphenyl) terephtalate (3). The compounds 4a-g were characterized using by IR, 1H-NMR, 13C-NMR and UV spectral data. In addition, 4 type compounds were titrated potentiometrically with tetrabutylammonium hydroxide in four non-aqueous solvents such as isopropanol, tert-butanol, dimethyl ketone, N,N-dimethylformamide and the half-neutralization potential values and the corresponding pKa values were determined for all cases.

Investigation of acidic properties of 2-ethoxy-6-(3-substitue-4,5-dihydro-1H-1,2,4-triazol-5-one-4-yl-azomethine)-phenyl benzoates

In this study, to determine the pKa values of 2-ethoxy-6-(3-substitue-4,5-dihydro-1H-1,2,4-triazol-5-one-4-yl-azomethine)-phenyl benzoates (1-9) were titrated potentiometrically with tetrabutylammonium hydroxide in four non-aqueous solvents such as isopropyl alcohol, tert-butyl alcohol, acetone and N,N-dimethylformamide (DMF), and graphs were drawn for all cases. In addition, the effects of solvents and molecular structure upon acidity compounds 1-9 were also determined and discussed. The half-neutralization potential values and the corresponding pKa values were determined by half neutralization method.

Non-Aqueous medium titrations of some 3-alkyl(aryl)-4-[3-(2-metylbenzoxy)-4-methoxybenzylideneamino]-4,5-dihydro-1H-1,2,4-triazol-5-ones

A series of 3-alkyl(aryl)-4-[3-(2-metylbenzoxy)-4-methoxybenzylideneamino]-4,5-dihydro-1H-1,2,4-triazol-5-ones (1-9) were titrated potentiometrically with tetrabutylammonium hydroxide in four non-aqueous solvents such as isopropyl alcohol, tert-butyl alcohol, acetonitrile and N,N-dimethylformamide (DMF), and graphs were drawn for all cases. The half-neutralization potential values and the corresponding pKa values were determined by half neutralization method. Thus, the effects of solvents and molecular structure upon acidity were discussed.

Synthesis, in vitro antioxidant activity, and physicochemical properties of novel 4,5-dihydro-1H-1,2,4-triazol-5-one derivatives

In this study, eight new 3-alkyl(aryl)-4-[4-(4-methylbenzoxy)benzylidenamino]-4,5-dihydro-1H-1,2,4-triazol-5-one (4) compounds were synthesized by the reactions of 3-alkyl(aryl)-4-amino-4,5-dihydro-1H-1,2,4-triazol-5-ones (3) with 4-(4-methylbenzoxy)benzaldehyde (1). The eight compounds were characterized using IR, 1H NMR, 13C NMR, and UV spectral data. In addition, the synthesized compounds were analyzed for their potential in vitro antioxidant activities, including reducing power, free radical scavenging and metal chelating activity. These antioxidant activities were compared to those from standard antioxidants, such as EDTA, BHA, BHT and α-tocopherol. Moreover, compounds 4 were titrated potentiometrically with tetrabutylammonium hydroxide in four non-aqueous solvents (isopropyl alcohol, tert-butyl alcohol, acetone and N,N-dimethylformamide). Thus, the half-neutralization potential values and the corresponding pKa values were determined in all cases. In addition, the lipophilicity of the synthesized compounds was investigated using HPLC. Kinetic parameters of the complexes were obtained for each stage of thermal degradation using the Coats–Redfern and Horowitz–Metzger methods.

Synthesis and biological evaluation of new 1,2,4-triazole derivatives with their potentiometric titrations

In the present study, 3-alkyl(aryl)-4-amino-4,5-dihydro-1H-1,2,4-triazol-5-ones (1a, b, d–g) reacted with 3-phenoxybenzaldehyde to afford 3-alkyl(aryl)-4-(3-phenoxy-benzylidenamino-4,5-dihydro-1H-1,2,4-triazol-5-ones (2a, b, d–g). Then, the acetylation reactions of compounds 2a and 2d–g were investigated. The structures of 11 new compounds were established from the elemental analysis, IR, 1H NMR, 13C NMR, MS, and UV spectral data. The synthesized compounds were analyzed for their in vitro potential antioxidant activities in three different methods. Compounds 2f and 3d showed best activity for the iron binding. Moreover, the compounds 2 were titrated potentiometrically with tetrabutylammonium hydroxide in four non-aqueous solvents (isopropyl alcohol, tert-butyl alcohol, acetonitrile, and N,N-dimethyl formamide). Thus, the half-neutralization potential values and the corresponding pKa values were determined in all cases. Furthermore, these 11 new compounds and 13 recently reported 3-alkyl(aryl)-4-(2-thienylmethyleneamino)-4,5-dihydro-1H-1,2,4-triazol-5-ones (4a–g) and 1-acetyl-3-alkyl(aryl)-4-(2-thienylmethyleneamino)-4,5-dihydro-1H-1,2,4-triazol-5-ones (5a, b, d–g) were screened for their antimicrobial activities.

Antioxidant activities and acidic properties of some novel 4-[3,4-di-(4-nitrobenzoxy)-benzylidenamino]-4,5-dihydro-1H-1,2,4-triazol-5-one derivatives

In this study, seven new 3-alkyl(aryl)-4-[3,4-di-(4-nitrobenzoxy)-benzylidenamino]-4,5-dihydro-1H-1,2,4-triazol-5-ones (4) were synthesized by the reactions of 3-alkyl(aryl)-4-amino-4,5-dihydro-1H-1,2,4-triazol-5-ones (2) with 3,4-di-(4-nitrobenzoxy)-benzaldehyde (3) which had also been synthesized by the reactions of 3,4-dihydroxybenzaldehyde with 4-nitrobenzoyl chloride by using triethylamine. The acetylation reactions of compounds 4 were investigated and six new 5 type compounds were obtained. The new thirteen compounds were characterized by elemental analyses and IR, 1H NMR, 13C NMR, UV and mass spectral data. In addition, the synthesized compounds were analysed for their in vitro potential antioxidant activities in three different methods. Compound 4g showed the best activity for antioxidant results. Moreover, the compounds 4 were titrated potentiometrically with tetrabutylammonium hydroxide (TBAH) in four non-aqueous solvents. Thus, the half-neutralization potential values and the corresponding pKa values were determined in all cases.

Microwave assisted synthesize of new some benzimidazole derivatives and determination of protonation constant of these compounds in non-aqueous media

A series of 2-substituted benzimidazole derivatives have been synthesized via microwave mediated process. Different benzimidazole derivatives were titrated with tetrabutylammonium hydroxide in four non-aqueous solvents (isopropyl alcohol, N , N -dimethylformamide,tert-butyl alcohol and acetonitrile), using potentiometric method. The half neutralization potential values and the corresponding pKa values were determined for all cases.

Preparation, GIAO NMR calculations and acidic properties of some novel 4,5-dihydro-1H-1,2,4-triazol-5-one derivatives with their antioxidant activities.

Six novel 3-alkyl(aryl)-4-(p-nitrobenzoylamino)-4,5-dihydro-1H-1,2,4-triazol-5- ones (2a-f) were synthesized by the reactions of 3-alkyl(aryl)-4-amino-4,5-dihydro-1H- 1,2,4-triazol-5-ones (1a-f) with p-nitrobenzoyl chloride and characterized by elemental analyses and IR, (1)H-NMR, (13)C-NMR and UV spectral data. The newly synthesized compounds 2 were titrated potentiometrically with tetrabutylammonium hydroxide in four non-aqueous solvents such as acetone, isopropyl alcohol, tert-butyl alcohol and N,N-dimethylformamide, and the half-neutralization potential values and the corresponding pK(a) values were determined for all cases. Thus, the effects of solvents and molecular structure upon acidity were investigated. In addition, isotropic (1)H and (13)C nuclear magnetic shielding constants of compounds 2 were obtained by the gauge-including-atomic-orbital (GIAO) method at the B3LYP density functional level. The geometry of each compound has been optimized using the 6-311G basis set. Theoretical values were compared to the experimental data. Furthermore, these new compounds and five recently reported 3-alkyl-4-(2-furoylamino)-4,5-dihydro-1H-1,2,4-triazol-5-ones (3a-c,e,f) were screened for their antioxidant activities.

Determination of relative acidity scales for some dipolar aprotic solvents by coulometry using a hydrogen-palladium electrode

A coulometric-potentiometric procedure for the determination of relative acidity scales of acetone, methylethyl ketone, methyl-isobutyl ketone and propylene carbonate is described. The range of the relative acidity scale of a solvent was determined from the difference between the half-neutralization potential of perchloric acid and that of tetrabutylammonium hydroxide. The perchloric acid was generated in situ from a hydrogen-palladium electrode in presence of sodium perchlorate or tetrabutylammonium perchlorate as the supporting electrolyte. The electrode pairs glass-SCE and (H2/Pd)ind-SCE were applied for the measurement of the half-neutralization potentials of the acid and base. A wider range of relative acidity scale of the solvents was obtained with the glass-SCE electrode pair and tetrabutylammonium perchlorate as the supporting electrolyte.

A Study on 4-Acylamino-4,5-dihydro-1H-1,2,4-triazol-5-ones

Five novel 3-alkyl-4-phenylacetylamino-4,5-dihydro-1H-1,2,4-triazol-5-ones (2) were synthesized by the reactions of 3-alkyl-4-amino-4,5-dihydro-1H-1,2,4-triazol-5-ones (1) with phenylacetyl chloride and characterized by elemental analyses and IR, 1HNMR, 13C-NMR and UV spectral data. The newly synthesized compounds 2 were titrated potentiometrically with tetrabutylammonium hydroxide in four non-aqueous solvents such as isopropyl alcohol, tert-butyl alcohol, acetonitrile and N,N-dimethylformamide, and the half-neutralization potential values and the corresponding pKa values were determined for all cases. In addition, these new compounds and five recently reported 3-alkyl-4-(pmethoxybenzoylamino)-4,5-dihydro-1H-1,2,4-triazol-5-ones (3) were screened for their antioxidant activities.

Synthesis, determination of p Ka values and GIAO NMR calculations of some new 3-alkyl-4-( p-methoxybenzoylamino)-4,5-dihydro-1 H-1,2,4-triazol-5-ones

3-Alkyl-4-amino-4,5-dihydro-1 H-1,2,4-triazol-5-ones ( 2) reacted with p-methoxybenzoyl chloride to afford the corresponding 3-alkyl-4-( p-methoxybenzoylamino)-4,5-dihydro-1 H-1,2,4-triazol-5-ones ( 3). Five newly synthesized compounds have been characterized by elemental analyses, IR, 1H NMR, 13C NMR and UV spectral data. The newly synthesized compounds 3 were titrated potentiometrically with tetrabutylammonium hydroxide in four non-aqueous solvents such as acetonitrile, isopropyl alcohol, tert-butyl alcohol and N, N-dimethylformamide, and the half-neutralization potential values and the corresponding p K a values were determined for all cases. Thus, the effects of solvents and molecular structure upon acidity were investigated. In addition, isotropic 1H and 13C nuclear magnetic shielding constants of compounds 3 were obtained by the gauge-including-atomic-orbital (GIAO) method at the B3LYP density functional level. The geometry of each compound has been optimized using the 6-311G basis set. Theoretical values were compared to the experimental data.

Synthesis and Non-Aqueous Medium Titrations of Some New 4-Benzylidenamino-4,5-dihydro-1H-1,2,4-triazol-5-one Derivatives

The synthesis of 3-alkyl(aryl)-4-(3-ethoxy-4-hydroxybenzylidenamino)-4,5-dihydro-1H-1,2,4-triazol-5-ones 3 from the reactions of 3-alkyl(aryl)-4-amino-4,5-dihydro-1H-1,2,4-triazol-5-ones 2 with 3-ethoxy-4-hydroxybenzaldehyde is described. The acetylation and methylation reactions of the compounds 3 giving compounds of type 4 and 5, respectively, were investigated. The newly synthesized compounds were characterized using elemental analyses and IR, 1H-NMR, 13C-NMR and UV spectral data. In addition, to investigate the effects of solvents and molecular structure upon acidity, compounds 3 were titrated potentiometrically with tetrabutylammonium hydroxide in four non-aqueous solvents (isopropyl alcohol, tert-butyl alcohol, acetonitrile and N,N-dimethylformamide). The half-neutralization potential values and the corresponding pKa values were determined for all cases.

Synthesis and Determination of pKa Values of Some New 3,4-Disubstituted-4,5-Dihydro-1H-1,2,4-triazol-5-one Derivatives in Non-aqueous Solvents

3-Alkyl(Aryl)-4-amino-4,5-dihydro-1H-1,2,4-triazol-5-ones (2) reacted with 2-furoyl chloride and thiophene-2-carbonyl chloride to afford the corresponding 3- alkyl(aryl)-4-(2-furoylamino)-4,5-dihydro-1H-1,2,4-triazol-5-ones (3) and 3-alkyl(aryl)- 4-(2-thienylcarbonylamino)-4,5-dihydro-1H-1,2,4-triazol-5-ones (4), respectively. The new compounds synthesized were characterized by using IR, 1H-NMR, 13C-NMR and UV spectral data together with elemental analysis. In addition, to investigate the effects of solvents and molecular structure upon acidity, compounds 3 and 4 were titrated potentiometrically with tetrabutylammonium hydroxide in four non-aqueous solvents (isopropyl alcohol, tert-butyl alcohol, N,N-dimethylformamide and acetonitrile). The half-neutralization potential values and the corresponding pKa values were determined for all cases.

Synthesis and Potentiometric Titrations of Some New 4-(Benzylideneamino)-4,5-dihydro-1H-1,2,4-triazol-5-one Derivatives in Non-Aqueous Media

The synthesis of 3-alkyl(aryl)-4-[4-(dimethylamino)benzylideneamino]-4,5-dihydro-1H-1,2,4-triazol-5-ones (3) from the reactions of 3-alkyl(aryl)-4-amino-4,5-dihydro-1H-1,2,4-triazol-5-ones (2) with 4-(dimethylamino)benzaldehyde is described. The newly synthesized 3 type compounds were titrated potentiometrically with tetrabutylammonium hydroxide in three non-aqueous solvents, including acetonitrile, isopropyl alcohol and N,N-dimethylformamide. The half-neutralization potential values and the corresponding pKa values were determined for all cases. Thus, the effects of solvents and molecular structure upon acidity were investigated. In addition, N-acetyl derivatives of 3 type compounds were also obtained. The new synthesized compounds in the study were fully characterized.

Titrations in non-aqueous media: potentiometric investigation of symmetrical and unsymmetrical tetra-aryl porphyrins with 4-nitrophenyl and 4-aminophenyl substituents in nitrobenzene solvent

The basicity of the symmetrical and unsymmetrical tetraphenylporphyrins, namely 5,10,15,20-tetraphenylporphyrin (I) (references), 5-(4-nitrophenyl)-10,15,20-triphenylporphyrin (II), a mixture of 5,10-bis(4-nitrophenyl)-15,20-diphenylporphyrin and 5,15-bis(4-nitrophenyl)-10,20-diphenylporphyrin (III), 5,10,15-tris(4-nitrophenyl)-20-phenylporphyrin (IV), 5,10,15,20-tetrakis(4-nitrophenyl)porphyrin (V), 5-(4-aminophenyl)-10,15,20-triphenylporphyrin (VI), a mixture of 5,10-bis(4-aminophenyl)-15,20-diphenylporphyrin and 5,15-bis(4-aminophenyl)-10,20-diphenylporphyrin (VII), 5,10,15-tris(4-aminophenyl)-20-phenylporphyrin (VIII) and 5,10,15,20-tetrakis(4-aminophenyl)porphyrin (IX), was investigated potentiometrically in nitrobenzene solvent. This investigation showed that these compounds are basic rather than acidic. Although they can not be titrated even with tetrabuthylammonium hydroxide, they can easily be titrated with perchloric acid to give well shaped and stoichiometric end-points. In addition they all undergo two proton reactions per porphyrin molecule. However, compounds VI, VII, VIII and IX each shows a second end-point to give three, four, five and six proton reactions, respectively, per porphyrin molecule. Half neutralization potentials (measures of their basicity) of these compounds are: I=368, II=409, III=432, IV=461, V=520, VI=340, VII=302, VIII=238 and IX=225 mV versus Ag/AgCl in methanol. These potentials clearly indicate that, if para-hydrogen with respect to the porphyrin core of tetraphenylporphyrin (I) is replaced with an acidifying nitro group (II, III, IV and V) the basicity of I decreases. This decrease is approximately proportional to the number of nitro groups. Each nitro group decreases the half neutralization potential by about 35 mV. On the other hand, if para-hydrogen indicated above is replaced with a basifying amino group (VI, VII, VIII and IX) the basicity increases. This increase is also approximately proportional to the number of amino groups. Each amino group increases the half neutralization potential by about 36.7 mV. The values 35 and 36.7 mV indicate that in nitrobenzene solvent the electron releasing power of an amino group to the porphyrin system is a little stronger than the electron withdrawing power of a nitro group from the porphyrin system. All these observations reveal that the nitrogen atoms at the core of the porphyrin molecules are strongly influenced by changes at the periphery of the molecules, which is a very good indication that the substituted phenyl groups and the cores of the porphyrins are nearly in the same plane.

Nonaqueous potentiometry for analyses of nitrogen bases from asphaltite and oil shale pyrolysis products

Two asphaltites and two oil shale samples were pyrolysed using a Heinze retort at 540°C. The asphaltites and oil shales gave medium and high oil yields. The oils produced from the retorting of asphaltites and oil shales are more complex than crude petroleum. During pyrolysis hydrogen, ethene, C 1-C 4 alkanes and hydrogen sulphide are formed. The pyrolysis products consist of complex mixtures of aliphatic, polycyclic aromatic and polar aromatic compounds containing significant quantities of nitrogen, sulphur and oxygen. Nitrogen-containing compounds which are found in the pyrolysis products have been investigated by nonaqueous potentiometric titration. A scheme based on p K a and half neutralization potential is presented for classifying nitrogen compounds in pyrolysis products into three different types. A combination of acetylation with titration in chlorobenzene differentiates the nitrogen bases, making it possible to characterise complex mixtures and quantitatively to determine combinations of two or more nitrogen bases.

Nonaqueous potentiometry of coal-derived asphaltenes and model nitrogen-containing compounds in acetophenone and nitrobenzene

A series of 34 nitrogen-containing compounds with a wide range of basicities was examined under differential nonaqueous potentiometric conditions in acetophenone and nitrobenzene. These compounds could be resolved into five classes based on pKaand half-neutralization-potential (HNP) values. Asphaltenes isolated from the vacuum still overhead (VSO) and vacuum still bottoms (VSB) fractions of the H-coal process were titrated under similar conditions. The titration results of both asphaltenes indicated the presence of two classes of nitrogen-containing compounds, a titratable class of the pyridine-ring or aniline type and a nontitratable class.

Titration of Acids and Acid Mixtures in Benzene-Acetonitrile Binary Solvent System

In this investigation, the half-neutralization potential of a series of acids of varying pKa was determined in the benzene-acetonitrile solvent system. The half-neutralization potential value of the acids was related to the pKa in a series of benzene-acetonitrile mixtures covering a range of dielectric constants (Dm = 5–35). The slopes of these straight-line relationships were then related to the dielectric constants of the solvent mixtures. The solvent mixture showing the maximum slope (Dm = 30) was used as a differentiating solvent for titrating binary and ternary sulfonamide mixtures.

Relationship between pKa (H<SUB>2</SUB>O) of 5-Substituted-4-amino-2-methylpyrimidines and Half Neutralization Potential and the Behavior of the Compounds in Nonaqueous Solvents

Relationship between pKa (H<SUB>2</SUB>O) of 5-Substituted-4-amino-2-methylpyrimidines and Half Neutralization Potential and the Behavior of the Compounds in Nonaqueous Solvents

Studies on heterocyclic compounds. II. Relations between half neutralization potential in non-aqueous titration and pKa (H2O) of purine and pyrimidine derivatives

Studies on heterocyclic compounds. II. Relations between half neutralization potential in non-aqueous titration and pKa (H2O) of purine and pyrimidine derivatives