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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Conformation and intramolecular hydrogen bonding of 2-chloroacetamide as studied by microwave spectroscopy and quantum chemical calculations
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Conformation and intramolecular hydrogen bonding of 2-chloroacetamide as studied by microwave spectroscopy and quantum chemical calculations

机译：微波光谱法和量子化学计算研究的2-氯乙酰胺的构象和分子内氢键

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The microwave spectrum of 2-chloroacetamide (ClCH2CONH2) has been investigated at room temperature in the 19-80 spectral range. Spectra of the (ClCH2CONH2)-Cl-35 and (ClCH2CONH2)-Cl-37 isotopomers of one conformer, which has a symmetry plane (C, symmetry), were assigned. The amide group is planar, and an intramolecular hydrogen bond is formed between the chlorine atom and the nearest hydrogen atom of the amide group. The ground vibrational state, six vibrationally excited states of the torsional vibration about the CC bond, as well as the first excited state of the lowest bending mode were assumed for the (ClCH2CONH2)-Cl-35 isotopomer, whereas the ground vibrational state of (ClCH2CONH2)-Cl-37 was assigned. The CC torsional fundamental vibration has a frequency of 62(10) cm(-1), and the bending vibration has a frequency of 204(30) cm(-1). The rotational constants of the ground and of the six excited states of the CC torsion were fitted to the potential function V(z) = 16.1(< z(4)> + 2.3 < z(2)>) cm(-1), where z is a dimensionless parameter. This function indicates that the equilibrium conformation has C, symmetry. Rough values of the chlorine nuclear quadrupole coupling constants were derived as chi(aa) = -47.62(52) and chi(bb) = 8.22(66) MHz for the Cl-35 nucleus and chi(aa) = -34.6(10) and chi(bb) = 6.2(11) MHz for the Cl-37 nucleus. Ab initio and density functional theory quantum chemical calculations have been performed at several levels of theory to evaluate the equilibrium geometry of this compound. The density functional theory calculations at the B3LYP/6-311++G(3df,2pd) and B3LYP/cc-pVTZ levels of theory as well as A initio calculations at the MP2(F)/cc-pVTZ level predict correct lowest-energy conformation for the molecule, whereas the ab initio calculations at the QCISD(FC)/6-311G(d) and MP2(F)/6-311++G(d,p) levels predict an incorrect equilibrium conformation.
机译：在室温下以19-80的光谱范围研究了2-氯乙酰胺（ClCH2CONH2）的微波光谱。分配了具有对称平面（C，对称性）的一种构象异构体的（ClCH 2 CONH 2）-Cl-35和（ClCH 2 CONH 2）-Cl-37异构体的光谱。酰胺基是平面的，并且在酰胺基的氯原子和最近的氢原子之间形成分子内氢键。对于（ClCH2CONH2）-Cl-35异位异构体，假定其为CC键的基态振动状态，扭转振动的六个振动激发态以及最低弯曲模式的第一激发态，而（分配了ClCH 2 CONH 2）-Cl-37。 CC扭转基本振动的频率为62（10）cm（-1），弯曲振动的频率为204（30）cm（-1）。将地面和CC扭转的六个激发态的旋转常数拟合为势函数V（z）= 16.1（ + 2.3 ）cm（-1），其中z是无量纲参数。该函数表明平衡构象具有C，对称性。对于Cl-35原子核，氯核四极偶合常数的近似值为chi（aa）= -47.62（52）和chi（bb）= 8.22（66）MHz，chi（aa）= -34.6（10） Cl-37核的chi（bb）= 6.2（11）MHz。从头计算和密度泛函理论已经在几个理论水平上进行了量子化学计算，以评估该化合物的平衡几何形状。在B3LYP / 6-311 ++ G（3df，2pd）和B3LYP / cc-pVTZ水平的密度泛函理论计算以及在MP2（F）/ cc-pVTZ水平的A从头计算可以预测正确的最低分子的能量构象，而在QCISD（FC）/ 6-311G（d）和MP2（F）/ 6-311 ++ G（d，p）水平上的从头算是预测不正确的平衡构象。

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