Abstract: Molecular conformation plays an essential role in the activity of monosulfuron. To understand the conformational conversion, especially how to convert to an active conformation, herein, the conformational behavior in water, n-octanol and n-octane solutions, the interaction energies with these three different solvents and hydrogen bond interaction with solvents of monosulfuron were investigated by a series of molecular dyna-mics simulations. The simulation results indicate that dominative conformations were different in different solvents, and the conformational conversion, especially converting to an active conformation, was mainly occurs in the aqueous solution in the plant. The calculation results also implies that the interaction between the monosulfuron and solvents was main factor which determined the conformational behavior of monosulfuron. The NH group in the sulfonylurea bridge may interact with the solution which has hydrogen bond acceptor atoms through hydrogen bond, and the competition between forming internal N—H…N hydrogen bond and forming hydrogen bond with solution was probably the driven force from crystal conformation to active conformation conversion.

Key words: Monosulfuron, Molecular dynamics simulation, Solution, Conformation, Hydrogen bond