Abstract The reaction between chlorimuron ethyl (CE) herbicide and the HEThDP− intermediate is addressed with the tools of computational chemistry, molecular dynamics and quantum chemistry, in order to check the postulated hypothesis that the inhibition of AHAS could proceed via a nucleophilic aromatic substitution reaction between HEThDP− and chlorimuron ethyl. The obtained results agree well with the empirical evidence for the inhibition process of AHAS by sulfonylureas, supporting the idea that the inhibition process could proceed by this via. It is also found that the nucleophilic attack of the Cα of the intermediate on the ipso carbon of the herbicide pyrimidinic ring is the rate-limiting step.