HOMOCONJUGATED HYDROGEN-BONDS WITH AMIDINE AND GUANIDINE BASES - OSMOMETRIC, POTENTIOMETRIC AND FTIR STUDIES

Five very strong N bases, 1,5-diazabicyclo[4.3.0]non-5-ene (DBN), pK(a ), = 23.4; 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), pK(a) = 23.9; tet ramethylguanidine (TMG), pK(a) = 23.3; 2-phenyl-tetramethylguanidine ( PhTMG), pK(a) = 20.6; and 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (MTBD), pK(a) = 24.97; have been studied by osmometric measurements w hich showed that they are monomeric in acetonitrile solutions. The con stants of the formation of homoconjugated complexes were determined by potentiometric measurements. In the IR spectra of the semi-protonated complexes of DBN, DBU and TMG, the homoconjugated N+-H ... N reversib le arrow N ... H-N+ hydrogen bonds cause broad band complexes in the r egion 3200-2500 cm(-1) instead of the expected continua. This spectral peculiarity is discussed.