Molecular structure of tryptamine in gas phase according to gas electron diffraction method and quantum chemistry calculations

The molecular structure of tryptamine was studied by gas-phase electron diffraction (GED) and quantum chemical calculations (DFT/B3LYP and MP2 methods with cc-pVTZ basis set). The best fit of the experimental scattering intensities (R-factor = 3.8%) was obtained for the four-conformer model. The experimental structural parameters are found to be in good agreement with the results of theoretical calculations. The geometric parameters of gaseous tryptamine are compared with those in the crystal phase. The standard enthalpy of formation of tryptamine in the gas phase was calculated using Gaussian-4 theory, yielding value of 133.6 +/- 33 kJ/mol. (C) 2017 Elsevier B.V. All rights reserved.