Synthesis And Insecticidal Activity Of Sucrose Esters

Recently, sucrose esters (SE) from C₆ to C₁₂, which can be biodegraded into sucrose andfatty acid, are found to have excellent insecticidal activities against the aphid and whitefly.Moreover, SE products are nontoxic to humans, crops and higher animals. They are anenvironmental insecticide, which appear to be prosperous commercial development, and theyare significant to agriculture in our country.Although there were few studies on synthesis of insecticidal sucrose esters in China, anovel class of insecticidal sucrose esters, including sucrose octanoate, sucrose dodecanate andsucrose caproate were synthesized by different method. Among the three products, sucroseoctanoate was synthesized by non-solvent method, sucrose octanoate and sucrose laurate wereprepared under the condition of reduced pressure with solvent method, sucrose caproate wasobtained by acid chloride method. According to their yields and Lymantria dispar grubsmortalities, sucrose octanoate was chosen to be the target product, which was synthesized bythe trans-esterification method (solvent method) under reduced pressure. The fouctional groupsof SE were showed by FTIR.Three kinds of fractions were fractionated and obtained in the solvent system ofdichloromethane and methanol by means of the column chromatography and thin layerchromatography test. Sucrose octanoate and each fraction were identified by MS, ¹H NMR andGC. It was proven that the three fractions were monoester, diester and triester, respectively, andthe content of monoester was 61.72%.The bioassay of the separated monoester, diester, triester and synthetic sucrose octanoatewere evaluated against the Lymantria dispar 1-year grubs. As a result, the monoester showedthe best insecticidal activity, and the corrected mortality was 72.9% in the 12mg/mL watersolution of sucrose octanoate. The corrected insects reduced rate of Aphis glycines Matsumurareached above 80% in the 12mg/mL water solution of sucrose octanoate after treating 5 days.The results indicated that sucrose octanoate possesses a good and potential insecticidal activity.The optimum condition was discussed by the single factor and orthogonal experiments.When the absolute pressure in the reaction chamber was 11 kPa, reacting ethyl octanoate withsucrose in the dimethyl sulfoxide (DMSO) yielded optimum results, the yield after 4 hours was79.11% under the conditions of the molar ratio of 2:1 between sucrose and ethyl octanoate,105～110℃reaction temperature and 16% (mass percent) anhydrous potassium carbonatecatalyst accounted for ethyl octanoate. Additionally, the synthesized sucrose octanoate hassuface activity with the tests of surface tension, degree of substitute, acid value, HLB andemulsifing ability.