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在CAM-B3LYP/6-311+G*水平,研究了气相中环状寡聚D-乳酸的几何结构、能量学特征和谱学性质,并进行了概念密度泛函分析。环状结构中存在3种不同类型的分子内氢键。PDLA6结构中的甲基基本在环的同一侧,偶极矩大;PDLA5的甲基在两侧均衡分布,偶极矩较小。PDLA4是能量学上最有利的结构。当聚合度n为偶数时,随着n的增大PDLAn的??G呈阶梯状增加,?ε呈阶梯状减小;当n为奇数时,也存在相同的现象。环状寡聚D-乳酸结构中C=O、COO―H和O―H键的伸缩振动频率与实验值相比,发生蓝移。PDLA6的电负性和亲电指数均为最大,表现出的酸性最弱。
At the level of CAM-B3LYP / 6-311 + G *, the geometrical structures, energetic characteristics and spectroscopic properties of the cyclic oligomeric D-lactic acid in the gas phase were studied and the concept of density functional analysis was carried out. There are 3 different types of intramolecular hydrogen bonds in the cyclic structure. PDLA6 structure of the base is basically the same side of the ring, the dipole moment is large; PDLA5 the methyl on both sides of the balanced distribution, smaller dipole moment. PDLA4 is the energetically most favorable structure. When the degree of polymerization n is even, G increases with the increase of n in step, and ε decreases in a stepwise manner. The same phenomenon occurs when n is odd. Cyclic oligomeric D-lactic acid structure C = O, COO-H and O-H bond stretching vibration frequency and the experimental value, a blue shift. PDLA6 has the highest electronegativity and electrophilic index, showing the weakest acidity.