Adnan Kenar

The non-aqueous titrimetric assay of the selected anti-inflammatory agents using tetra-n-butylammonium hydroxide as titrant.

A potentiometric titration method in non-aqueous media is proposed for the determination of some commonly used anti-inflammatory agents. The direct potentiometric titration of three anti-inflammatory agents, namely mefenamic acid, fenbufen and ibuprofen; and the indirect potentiometric titration of diclofenac sodium was carried out in acetonitrile solvent using tetra-n-butylammonium hydroxide as titrant, at 25 degrees C and under a nitrogen atmosphere. The method was found to be highly accurate and precise, having a relative standard deviation of <1.0% for all anti-inflammatory agents studied. Also, it was shown that the method could be successfully applied to the assay of commercial pharmaceuticals containing the above-mentioned anti-inflammatory agents. The validity of the method was tested by the recovery studies of standard addition to pharmaceuticals and the results were found to be satisfactory. The proposed method is simple, rapid and sufficiently precise for quality control purposes.

Titrations in non-aqueous media. Part II. Basicity order of aliphatic amines in nitrobenzene solvent

The relative basicity order of methyl-, ethyl-, propyl- and butylamines has been determined potentiometrically with perchloric acid in nitrobenzene solvent and found to be R3N > R2NH > RNH2 > NH3, where R = Et, n-Pr or n-Bu. However, for the methylamines, the order is Me2NH Me3N > MeNH2 > NH3. The orders in primary, secondary and tertiary amines are EtNH2 > MeNH2 > n-PrNH2 > n-BuNH2 > NH3; Et2NH > Me2NH > n-Pr2NH > n-Bu2NH > NH3; and Et3N > n-Pr3N n-Bu3N > Me3N > NH3. These results show that, in general, an increase in the number of alkyl groups increases the basicity of the amine, and that an increase in the size of the alkyl group decreases the basicity. n-Butylamine is a stronger base than branched-chain primary butylamines.

Titrations in non-aqueous media. Part IV. Solvent effects on basicity of aliphatic amines

The relative basicity orders of methyl-, ethyl-, propyl- and butylamines have been measured potentiometrically with perchloric acid in cyclohexane and hexane solvents. The basicity orders of the amines in the series, including ammonia, were found to be NH3 > MeNH2 > Me2NH > Me3N; NH3 > EtNH2 > Et2NH > Et3N; NH3 > n-PrNH2 > n-Pr2NH > n-Pr3N; NH3 > n-BuNH2 > n-Bu2NH > n-Bu3N; and n-BuNH2 > i-BuNH2 > sec-BuNH2 > t-BuNH2. In addition to these, some interesting orders have also been found among primary, secondary and tertiary amines, e.g., MeNH2 > EtNH2 > n-PrNH2 > n-BuNH2; Me2NH > Et2NH > n-Pr2NH > n-Bu2NH; Me3N > Et3N > n-Pr3N > n-Bu3N; and MeNH2 > EtNH2 > i-PrNH2 > t-BuNH2. From these findings four important results have been obtained as follows: (1) an increase in the number of alkyl group decreases the basicity; (2) an increase in the size of an alkyl group decreases the basicity; (3) amines containing unbranched alkyl groups are more basic than their branched analogues; and (4) an increase in the number of methyl substituents on the methyl group of methylamine decreases the basicity in a regular manner. These results contradict results reported in the literature and also earlier results obtained in this laboratory.

Conductimetric titrimetry for assay of selected antibiotics in non-aqueous media

In this study, a conductimetric titration method is proposed for the determination of some commonly used antibiotics. The conductimetric titration of three antibiotics, namely ampicillin, amoxycillin trihydrate and rifampin, was carried out in acetic acid using perchloric acid as titrant. Ciproflaxacin hydrochloride, however, was titrated after being dissolved in acetic acid containing an excess of mercury(II) acetate. For the titration of netilmicin sulphate, barium acetate prepared in acetic acid was used as titrant. The method was found to be highly accurate and precise, having a relative standard deviation of less than 1.0% for all antibiotics studied. It was also shown that the conductimetric titrimetry could be successfully applied to the assay of commercial preparations containing the above-mentioned antibiotics. The validity of the method was tested by the recovery studies of standard addition to pharmaceuticals and the results were found to be satisfactory.

Heterodinuclear Ni(II)—Sn(II) complexes from reduced ONNO type Schiff base compounds

N,N´-bis(salicylidene)-1,3-propanediamine (LH2), N,N´-bis(salicylidene)-2,2´- dimethyl-1,3-propane-diamine (LDMH2), N,N´-bis(2-hydroxyacetophenylidene)-1,3-propanediamine (LACH2), N,N´-bis(2-hydroxyacetophenone)-2,2´-dimethyl-1,3-propanediamine (LACDMH2) and N,N´-bis(salicylidene)-1,2-ethylenediamine (SalenH2) were reduced in methanolic media with the help of NaBH4. Ni(II)—Sn(II) heteronuclear complexes were synthesized according to the template method in DMF media. The complex structures were analyzed using elemental analysis, FTIR spectroscopy, thermogravimetry and X-ray diffraction. Appropriate crystals for one of the complexes 2 were obtained for X-ray diffraction. The Ni(II) ion has an octahedral coordination between the organic donors. The Sn(II) ion forms three membered coordination structure with phenolic oxygen atoms via μ-bridges. The Ni … Sn bridging distance is 3.1543(9) Å.

Titrations in non-aqueous media. Part III. Basicity order of aniline, N-Alkyl- and N-aryl-substituted anilines and pyridine in nitrobenzene solvent

The relative basicity order of ammonia, pyridine, aniline and N-methyl-, N,N-dimethyl-, N-ethyl-, N,N-diethyl-, N-aryl- and N,N-diaryl-substituted anilines have been determined potentiometrically with perchloric acid in nitrobenzene solvent and found to be NH3 > Py > PhNEt2 > PhNMe2 > PhNHEt > PhNHMe > PhNH2 > Ph2NH > Ph3N. This order in general conflicts with the results observed by other workers in either the gas phase or in the condensed phase. N-Alkyl substitution increases the basicity of the aniline, and N-aryl substitution decreases its basicity. Moreover, the number and size of the substituent influence the basicity of aniline. N-Ethyl-substituted anilines are more basic than the corresponding N-methyl-substituted anilines. The position of pyridine in the order is surprising and difficult to interpret.

SIMULTANEOUS DETERMINATION OF C60 AND C70 FULLERENES BY A SPECTROPHOTOMETRIC METHOD

In all fullerene-producing systems, reaction products were black soot extracts reported to contain a 5–25% fullerene mixture. Toluene extraction of the soot results in a solution of C60, C70, and higherc fullerenes. Without separation, absolute determination of the contents is not possible, leaving the researcher to comment only on the C60/C70 ratio of the solution. High-performance liquid chromatography, nuclear magnetic resonance, and scanning tunneling microscopy imaging techniques were reported in the literature for determining the C60/C70 ratio of the mixtures. These methods require tedious experiments and produce slightly differing results as well. In this communication, a new and relatively quick method is proposed for the simultaneous determination of the yields of C60 and C70 (not the ratio) in fullerene-containing solutions by ultraviolet-visible spectrophotometric analysis.

Titrations in non-aqueous media. Part IX. Potentiometric titrations of symmetrical aliphatic diamines and their Schiff bases in different solvents

Four aliphatic symmetrical diamines (1,2-diaminoethane, 1,3-diaminopropane, 1,4-diaminobutane and 1,6-diaminohexane) plus hydrazine and their Schiff bases with salicylaldehyde were titrated potentiometrically with perchloric acid in acetonitrile, nitrobenzene and acetic acid solvents. 1,2-Diaminoethane and 1,3-diaminopropane were titrated stepwise in acetonitrile, but not in nitrobenzene and acetic acid solvents. An increase in the number of methylene groups between the two amino groups increased the basicity. The basicity order of these diamines, extracted from the second half of the titration curves in all solvents, and also for their Schiff bases, was 1,6-diaminohexane > 1,4-diaminobutane > 1,3-diaminopropane > 1,2-diaminoethane > hydrazine. Among the Schiff bases, only N,N′-bis(salicylidene)-1,2-diaminoethane could be titrated differentially in acetonitrile and nitrobenzene solvents. N,N′-Bis(salicylidene)hydrazine could not be titrated even in acetic acid. However, the same compounds could be titrated in acetonitrile and nitrobenzene. Acetic acid had a very strong levelling effect on the basicity on both sides of the potential range.

Potentiometric determination of relative basicities of aliphatic amines in pyridine

Abstract Potentiometric titrations of methyl-, ethyl-, n -propyl-, n -butylamines and ammonia were carried out in pyridine using a standardized tetrabutylammonium hydroxide solution. The relative basicities were found in all cases to be in the order RNH 2 > R 2 NH > R 3 N , R being an alkyl group. Basicity of any amine was assumed to be the sum of the inductive contribution of alkyl group(s) and a contribution from pyridine solvent through hydrogen bonding. On this assumption, the experimental basicity order was rationalized. The order in pyridine is different from the order of gas phase basicities.

Titrations in non-aqueous media. Part VII. Effects of substituents on basicity of aniline

The basicities of 22 derivatives of aniline with methyl, amino, hydroxy, chloro, bromo, iodo, nitro and carboxy substituents were determined potentiometrically against a standard in nitrobenzene solvent. Methyl, amino and hydroxy substituents had a basicity-increasing effect and the others a basicity-decreasing effect on aniline. The basicity-increasing effects of each substituent differs depending on whether it is at the ortho, meta or para position. The basicity-increasing order of methyl and amino substituents is p > m > o, whereas that of the hydroxy substituent is p > o > m. Halogens, nitro and carboxy substituents all decrease the basicity of aniline. The basicity-decreasing order of the halogens is o > m > p, and moreover is in the order l > Br > Cl for para derivatives and Br > Cl for ortho and meta derivatives. The basicity-decreasing effect of a nitro substituent is in the order o > p > m, whereas that of a carboxy substituent is p > o > m. Among the isomers of ortho-and para-orienting substituents, para isomers, and among the isomers of meta-orienting substituents meta isomers are the most basic. Of the substituents, the basicity-increasing effects decrease in the order NH2 > OH > CH3 and the basicity-decreasing effects in the order NO2 > COOH > l > Br > Cl.