title: Microwave spectrum, conformational composition, and intramolecular hydrogen bonding of (2-chloroethyl)amine (ClCH2CH2NH2).
abstract: The microwave spectrum of (2-chloroethyl)amine, ClCH(2)CH(2)NH(2), has been investigated in the 22-120 GHz region. Five rotameric forms are possible for this compound. In two of these conformers, denoted I and II, the Cl-C-C-N chain of atoms is antiperiplanar, with different orientations of the amino group. The link of the said atoms is synclinal in the three remaining forms, III-V, which differ with respect to the orientation of the amino group. The microwave spectra of four of these conformers, I-IV, have been assigned. In two of these rotamers, III and IV, the amino group is oriented in such a manner that rare and weak five-membered N-H···Cl intramolecular hydrogen bonds are formed. The geometries of conformers I and II preclude a stabilization by this interaction. The energy differences between the conformers were obtained from relative intensity measurements of spectral lines. The hydrogen-bonded conformer IV represents the global energy minimum. This rotamer is 0.3(7) kJ/mol more stable than the other hydrogen-bonded conformer III, 4.1(11) kJ/mol more stable than II, and 5.5(15) kJ/mol more stable than I. The spectroscopic work has been augmented by quantum chemical calculations at the CCSD/cc-pVTZ and MP2/6-311++G(3df,3pd) levels of theory. The CCSD rotational constants and energy differences are in good agreement with their experimental counterparts.
authors: Centre for Theoretical and Computational Chemistry (CTCC), Department of Chemistry, University of Oslo, Oslo, Norway. harald.mollendal@kjemi.uio.no
authors: Harald
authors: H
authors: Møllendal
authors: Svein
authors: S
authors: Samdal
authors: Jean-Claude
authors: JC
authors: Guillemin
mesh_terms: D005021:Ethylamines / Q000737:chemistry*; D006860:Hydrogen Bonding; D008872:Microwaves; D008968:Molecular Conformation; D011789:Quantum Theory
chemical_list: C560144:(2-chloroethyl)amine; D005021:Ethylamines