Milton J. Kornet

Alkylation of Carboxylate Salts of Acidic Herbicides for Gas Chromatographic Analysis

Abstract The methyl esters of 2-methoxy-3, 6-dichlorobenzoic acid and three phenoxyacetic acids were prepared by the admixture of an excess of both methyl iodide and anhydrous alkali-metal carbonate to a solution of the carboxylic acids in acetone. The reaction was completed within the shortest period of time when cesium carbonate was used, and the reaction mixture was injected without further work-up into a gas chromatograph fitted with a flame ionization detector. Further reduction of reaction time was achieved by heating the mixture to 50°C and by ultrasonic treatment; this technique is also suitable for esterification of microliter quantities and obviates the need for a microrefluxer. Butylesters of 2, 4-D and 2, 4, 5-T were prepared in an analogous manner. The methyl esters of 2, 4-D and 2, 4, 5-T, and the butyl ester of 2, 4-D were obtained in better than 90% yield.

Preparation of Hydrazides Using Silicon Tetrachloride as Coupling Agent1

Abstract Silicon tetrachloride proved to be an effective reagent for the preparation of hydrazides from carboxylic acids. Yields were comparable to those obtained via N,N′-dicyclohexylcarbodiimide (DCC) and the procedure was used to synthesize some hydrazides which are difficult to obtain otherwise.

Confirmation and analysis of s-chlorotriazines by derivatization with pyrrolidine

Abstract Atrazine and simazine were analyzed and confirmed via their pyrrolidino derivatives by gas chromatography on SPWax-10 megabore column using a NP-detector and propazine as the internal standard. The s -chlorotriazines were reacted in dimethylformamide with an excess of pyrrolidine at 60°C for 30 minutes to afford practically quantitative substitution of the chlorine. The retention times of the derivatives were increased markedly compared to those of the parent compounds. Reproducibility as measured by response ratios relative to the propazine derivative was very good: C.V. for atrazine and simazine were 0.60% and 0.26% respectively (n = 5). Good linearity was seen at 0.4 to 2.2 ng/μL concentration: measured in duplicate at 4 dilutions, the coefficient of determination r2 was 0.9998 for atrazine derivatives and 0.9994 for simazine derivatives. Very good agreement was found when analytical results were correlated with data obtained by gas chromatography of the parent compounds.

In-Block Benzylation of Phenols by Benzyldimethylphenylammonium Chloride

Abstract Phenol, 2, 4, 5-trichlorophenol, 2, 3, 4, 6-tetrachlorophenol, pentachlorophenol, p.-nitrophenol, 2-naphthol, 8-hydroxyquinoline (Bioquin), and 2, 6-dibromo-4-cyanophenol (Bromoxynil) were analyzed as their benzyl ethers by gas chromatography using a flame ionization detector. The derivatives were formed by direct injection of 1 μl of a mixture of the phenols and a thousandfold measure (w/w) of benzyldimethylphenylammonium chloride in methylene chloride. Reproducibility of response and retention time was excellent and good linearity was observed at 12.5 to 50 ng/μl concentration of phenols. The reaction worked best with halo-genated phenols and appeared to be somewhat affected by alkyl substituents and steric hindrance; o-cresol and 2, 4-dinitro-6-sec.-butylphenol (Dinoseb) did not produce noticeable peaks. The limit of detection was around 2 ng. When using an electron-capture detector (solvent = toluene), 10 pg of pentachlorophenol was detectable, but the response was not linear. The procedure i...

In-Block Derivatization of Herbicidal Carboxylic Acids by Pentafluorobenzyl Bromide

Abstract Herbicidal carboxylic acids were analyzed via ECD gas chromatography of their pentafluorobenzyl esters. The derivatives were formed by direct injection of a mixture of the acids and pentafluorobenzyl bromide in acetone; yields showed marked dependence on pKa of the acids. Carboxylic acids which have pKa values greater than 4.5 yielded the corresponding derivatives in poor yield unless triethylamine is included in the mixture. The procedure is fast and particularly convenient for low-level screening, identification and analysis of highly acidic chlorobenzoic, chlorophenoxyalkanoic, and arylacetic acids in the presence of less acidic carboxylic acids and phenols.

Preparation of Amides of Carboxylic Acid Herbicides for Gas Chromatographic Analysis

Abstract Amides of 14 carboxylic acid herbicides were prepared by reacting the free acid with the amine in toluene for 1 hr at 80[ddot]C in the presence of PCl3 or P2I4. The acids include phenoxyacetic acids, arylacetic acids, and benzoic acids. Aniline, o-toluidine, 3,5-bis(trifluoromethyl)aniline, piperidine, and tetrahydroquinoline were the amine components. Excess of reagents and by-products of the reaction were removed by partitioning into aqueous acid and base. Retention times relative to 2,4-D anilide on 1% OV-22 and FSOT RSL-150 columns are listed for the anilides and should be useful for confirmation purposes. The anilides of 2,4-D, silvex and 2,4,5-T were obtained in better than 90% yield.