Analysis of the Proton, Carbon, and Nitrogen NMR Spectra of cis,cis- and cis,trans-1,3,5-Triaminocyclohexane

Article abstract of DOI:10.1002/mrc.1260231114

The proton spectrum of the isomeric mixture of cis,cis- and cis,trans-1,3,5-triaminocyclohexane was assigned with a 2D COSY experiment.Using Forrest's modified equation and the 2D J spectrum results, the conformations of the two isomers were analysed.The six-membered ring of the cis,trans isomer is flattened by 1,3-diaxial interactions between two amino substituents; in the cis,cis isomer, ring pucker is increased owing to non-bonded interaction between the equatorial amino groups and adjacent methylene protons.The 13C and 15N spin-lattice relaxation of the two isomeric 1,3,5-triaminocyclohexanes was also measured at different pH values; NH_x groups rotate faster with decreasing pH.Rotation/jump rates and barriers are reported, determined from the NT₁^DD ratios between 15N and 13C nuclei.