Reaction Conditions Necessary for Silylation of Herbicides

Abstract

The reaction conditions are described for preparation and gas chromatographic analysis of microgram quantities of the trimethylsilyl (TMS) esters of 3,6-dichloro-o-anisic acid (dicamba), (2,4-dichlorophenoxy)acetic acid (2,4-D), (2,4,5-trichlorophenoxy)acetic acid (2,-4.5-T), and 2 water-degradable polymers of 2,4,5-T. Silylation was efficient at 0, 22, and 55°C. A ratio of 1:10 silylating agent (N,O-bis-(trimethylsilyl)acetamide, BSA) to silylation solvent (dimethylformamide, DMF) was optimum for silylation of 2,4-D, 2,4,5-T, and 2,4,5-T polymers. A 1:50 ratio was best for silylation of dicamba. A 1:10 ratio (BSA/DMF) will tolerate up to 1.0 and 0.1% water in the silylation of 2,4-D and 2,4,5-T, respectively. A 1:50 ratio will tolerate up to 0.1% water in the silylation of dicamba. Silylated samples could be analyzed immediately after addition of the silylation reagent. Stability of silylated samples at 22°C was directly proportional to concentration; 1.0 μg samples showed no loss of activity 2.3 hr after reaction. TMS esters were chromatographed on a 6′ × ¼″ glass column containing 3% SE-30 on 80-100 mesh Chromosorb W(HP) at 230°C.

Comparative Effects and Concentration of Picloram, 2,4,5-T and Dicamba in Tissue Culture

“…Effectiveness of the herbicide treatment was based on the growth of treated tissue (fresh weight) compared to growth in the control. Internal concentration of herbicide in tissues was determined by using gas chromatograph techniques according to established methods for picloram and 2,4,5-T (6) and dicamba (1). The extraction of dicamba from the tissues was similar to that reported for picloram and 2,4,5-T. We used six replications for every treatment and each experiment was usually repeated.…”