Carbaryl insecticide conjugation onto chitosan via iodochitosan and chitosan carbonyl imidazolide precursors

Chitosan conjugated with 1-naphthyl methylcarbamate or carbaryl (CBR), were prepared by two molecular designs, i.e. without spacer via iodochitosan to obtain chitosan-carbaryl (Type 1, CHI-CBR), and with spacer by using N,Nʹcarbonyldiimidazole (CDI) to obtain chitosan acetate-carbonyl imidazolide-carbaryl (Type 2, CA-CDI-CBR). The chitosan precursors of Types 1 and 2 were accomplished for 50¯60% substitution as confirmed by FT-IR, NMR, and elemental analysis. The conjugation of carbaryl onto iodochitosan (Type I) was achieved via alkylation of Nsubstituted amide using NaH as a catalyst. The coupling reaction of carbaryl onto chitosan acetate was succeeded by carbonyl imidazolide which proceeded by nucleophilic substitution. The introduction of carbaryl was identified from the ester peak at 1707 cm-1 by FT-IR curve fitting technique.