Acid dissociation constants in water have been determined for proton loss f
rom a series of N-aryl-N'-cyanoguanidines 1. Treatment,of the same compound
s with a strong base, butyllithium, followed by excess methyl iodide leads
to successive N-methylation to yield mono-, di- and tri-methylated N-aryl-N
' -cyanoguanidines, The mechanism of the methylation is discussed.