Complete experimental and theoretical proton and carbon nuclear magnetic resonance spectral assignments, molecular structure and conformational study of 1‐cyclohexylpiperazine and 1‐(4‐pyridyl)piperazine

Abstract

The possible stable forms and molecular structures of 1-cyclohexylpiperazine (1-chpp) and 1-(4-pyridyl)piperazine (1-4pypp) molecules have been studied experimentally and theoretically using nuclear magnetic resonance(NMR) spectroscopy. (13)C, (15)N cross-polarization magic-angle spinning NMR and liquid phase (1)H, (13)C, DEPT, COSY, HETCOR and INADEQUATE NMR spectra of 1-chpp (C(10)H(20)N(2)) and 1-4pypp (C(9)H(13)N(2)) have been reported. Solvent effects on nuclear magnetic shielding tensors have been investigated using CDCl(3), CD(3) OD, dimethylsulfoxide (DMSO)-d(6), (CD(3))(2)CO, D(2)O and CD(2)Cl(2). (1)H and (13)C NMR chemical shifts have been calculated for the most stable two conformers, equatorial-equatorial (e-e) and axial-equatorial (a-e) forms of 1-chpp and 1-4pypp using B3LYP/6-311++G(d,p)//6-31G(d) level of theory. Results from experimental and theoretical data showed that the molecular geometry and the mole fractions of stable conformers of both molecules are solvent dependent.