The intramolecular hydrogen bonds in some Schiff bases derived from cyclopropyl-, cyclobutyl- and cyclopentylamine

Eight Schiff bases (N-(R-salicylidene)-cycloalkilamines, R=H, 5-NO2 and 5-Br) obtained from cyclopropyl, cyclobutyl- and cyclopentylamine were investigated in terms of intramolecular hydrogen bond formation in chloroform solution and in the solid state. The relationship between cycloalkyl ring size and proton position was discussed. For the compounds which exist as OH form (salicylaldehyde and 5-bromosalicylaldehyde derivatives), no correlation between ring size and proton position in hydrogen bond was found. For 5-nitro derivatives, the structure of hydrogen bridge strongly depends on the cycloaliphatic ring size.