6533b870fe1ef96bd12cfc9a

RESEARCH PRODUCT

Synthesis and influence of fatty acid esters on the foliar penetration of herbicides

subject

description

Abstract Synthesis of mono-esters of tetraethylene glycol and di-esters of tetraethylene glycol was accomplished from fatty acids and tetraethylene glycol in the absence of solvent and catalyst. Esterification was studied in a batch reactor by using a response surface methodology to evaluate the influence of synthesis variables such as molar substrate ratio of fatty acid relative to tetraethylene glycol (1.39–7.52), temperature (145–167°C), reaction time (0.5–8 h) on the yield of mono- and di-esters of tetraethylene glycol. A multipurpose reactor was developed for the transformation of fatty acids into pure α-monoglycerides. The 1-monoglycerides of heptanoic, undecelenic, oleic, linoleic and erucic acids and tetraethylene glycol esters, mono- and di-esters of undecelenic, mono- and di-oleic acids, were evaluated as co-formulants for the herbicides phenmedipham and 2,4- d . The test plants were chosen according to the structure of their epicuticular wax: amorphous in Galium aparine L. (cleavers), crystalline in barley (Hordeum vulgare L.) and pea (Pisum sativum L.). Foliar penetration studies were used as a rapid test for co-formulants. Some of the monoglycerides and the tetraethylene glycol esters studied showed a strong enhancing effect on the foliar penetration of 2,4- d and phenmedipham. In some cases, the extent of the effect seemed to depend on the relative lipophilicities of the ester and of the herbicide. The mono acyl glycerols impaired the crystallisation of phenmedipham but, with the exception of the undecelenic derivative, did not affect the diffusion of phenmedipham in model wax.