Solvent-free synthesis and crystal structures of s-cis and s-transN,N′-bis(2-hydroxycyclohexyl)ethane-1,2-diamine

The symmetrical amino alcohol synthesis via ring opening of cyclohexene oxide with ethylendiamine is illustrated by synthesis and characterization of β-amino alcohols s- cis -( SSSS )-cy 2 en ( 1 ) and s- trans -( SSRR )-cy 2 en ( 2 ) (cy 2 en = N , N ′-bis(2-hydroxycyclohexyl)ethane-1,2-diamine) in one step and with high yield. The reaction was carried out in a microwave reactor under solvent-free conditions. These products were characterized by IR and Raman spectroscopy, elemental analysis, thermal methods (TGA, DTG and DTA), mass spectrometry and 1 H and 13 C NMR spectroscopy. The crystal structures of 1 and 2 were determined by single crystal X-ray structural analysis, followed by DFT calculations. Intramolecular hydrogen bond was observed in 1 with C 2 symmetry, but not in 2 with C i symmetry. The nature of intramolecular hydrogen bond in 1 has been investigated by AIM and NBO analyses. The molecules in 1 are linked into an infinite chain along the [001] direction, giving rise to R 4 4 (8) graph-set motif, while the molecules in 2 are linked into a 2D network in the bc plane, giving rise to R 2 2 (10) and R 3 3 (12) motifs. The protonation equilibria of 1 and 2 have been studied by pH-potentiometry, with p K 1 9.01 and p K 2 5.50 determined for 1 and p K 1 8.58 and p K 2 5.26 determined for 2 .