CONFIGURATION OF AMIDINES AND FACTORS GOVERNING THEIR HYDROGEN-BONDING PATTERNS

On the basis of 22 amidine structures the rules governing the amidine cis-trans configuration are developed. In amidines the most bulky groups bonded to N1, N2 or Cl tend always to be in the trans position and the molecular configuration depends on the relative sizes of these substituents. The configuration is also the cause of the different hydrogen-bonding patterns in secondary formamidines (E,E configuration, cyclic dimers) and all other secondary amidines (EZ configuration, infinite chains bonded by N-H...N hydrogen bonds or linear dimers).