VANDERWAALS COMPLEXES IN 1,3-DIPOLAR CYCLOADDITION REACTIONS - OZONE ETHYLENE
VANDERWAALS COMPLEXES IN 1,3-DIPOLAR CYCLOADDITION REACTIONS - OZONE ETHYLENE
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DOI：
10.1021/ja00007a010
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发表时间：
1991-03-27
影响因子：
15
通讯作者：
CREMER, D
中科院分区：
文献类型：
--
作者：
GILLIES, CW;GILLIES, JZ;CREMER, D
用脉冲束法布里-珀罗腔傅里叶变换微波谱仪观测了O_3-CH_2=CH_2，O_3-Cd_2=CH_2，O_3-反式-CHD=CHD和O_3-cis-CHD=CHD的微波光谱。范德华络合物中的内部运动给出了正常的、1，1-双氢和反式-1，2-双氢同位素的两种状态。上述同位素物种的两种态的c型跃迁，以及观察到的一种O_3-cis-CHD=CHD的同位素形式，独立地符合不对称的顶部Watson哈密顿量。O_3-CH_2=CH_2的斯塔克效应测量给出了u_a=0.017(1)D和u_c=0.466(2)D。微波数据仅与具有C(S)对称性的结构相一致，在该结构中，乙烯和臭氧的近平行平面的质心间距为R(Cm)=3.290(3)埃。在MP4水平上的从头计算表明，首选的几何形状对应于臭氧和乙烯平面的小倾斜，这将一对外向的氢原子朝向臭氧的终端氧原子。理论和微波结果都表明，隧道分裂至少部分是由于乙烯绕其垂直于乙烯平面的C2轴180度旋转造成的。利用1，3偶极环加成理论、轨道对称性规则以及络合物和过渡态的从头算方法，论证了臭氧与乙烯反应的过渡态前，O_3-CH_2=CH_2在反应坐标上处于浅极小值，生成初级产物1，2，3-三氧杂环戊烷。
Microwave spectra of O3-CH2=CH2, O3-CD2=CH2, O3-trans-CHD=CHD, and O3-cis-CHD=CHD have been observed with a pulsed-beam Fabry-Perot cavity, Fourier transform microwave spectrometer. Internal motions in the van der Waals complex give two states for the normal, 1,1-dideuterated and trans-1,2-dideuterated isotopic forms. The c-type transitions of the two states for the isotopic species above, as well as the one observed isotopic form of O3-cis-CHD=CHD, independently fit to an asymmetric top Watson Hamiltonian. Stark effect measurements for O3-CH2=CH2 give mu-a = 0.017 (1) D and mu-c = 0.466 (2) D. The microwave data are only consistent with a structure having C(S) symmetry in which the nearly parallel planes of ethylene and ozone have a center of mass separation of R(cm) = 3.290 (3) angstrom. Ab initio calculations at the MP4 level indicate that the preferred geometry corresponds to small tilts of the ozone and ethylene planes, which place an exo-oriented pair of hydrogens toward the terminal oxygens of ozone. Both the theoretical and microwave results suggest the tunneling splitting arises at least in part from a 180-degrees rotation of ethylene about its C2 axis, which is perpendicular to the ethylene plane. 1,3-Dipolar cycloaddition theory, orbital symmetry rules, and ab initio calculations of the complex and transition states are used to argue that O3-CH2=CH2 lies in a shallow minimum on the reaction coordinate prior to the transition state in the reaction of ozone plus ethylene, which produces the primary product 1,2,3-trioxolane.