Centre for Theoretical and Computational Chemistry (CTCC), Department of Chemistry, University of Oslo, Oslo, Norway.
J Phys Chem A. 2011 May 5;115(17):4334-41. doi: 10.1021/jp201263c. Epub 2011 Apr 1.
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.
（2-氯乙基）胺，ClCH（2）CH（2）NH（2）的微波光谱已在 22-120GHz 区域进行了研究。该化合物可能有五种构象体。在这两种构象体 I 和 II 中，Cl-C-C-N 原子链呈反式平面，氨基的取向不同。在其余三种构象体 III-V 中，所述原子的键呈顺式，它们在氨基的取向上有所不同。这四种构象体中的四种构象体 I-IV 的微波光谱已被分配。在这两种构象体 III 和 IV 中，氨基的取向使得形成罕见且弱的五元 N-H···Cl 分子内氢键。这种相互作用使构象体 I 和 II 无法稳定存在。构象体之间的能量差异是通过谱线相对强度测量获得的。氢键构象体 IV 代表了全局能量最低点。这种构象体比其他氢键构象体 III 稳定 0.3（7）kJ/mol，比 II 稳定 4.1（11）kJ/mol，比 I 稳定 5.5（15）kJ/mol。光谱工作已通过 CCSD/cc-pVTZ 和 MP2/6-311++G（3df，3pd）理论水平的量子化学计算得到补充。CCSD 转动常数和能量差异与实验值吻合较好。
