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Yuan Man - One of the best experts on this subject based on the ideXlab platform.

Jiang Ping - One of the best experts on this subject based on the ideXlab platform.

  • Theoretical Study on Secondary Chemical Bond in Organo-metallic Compounds(V) Study on Formation of Secondary Chemical Bond by Molecular Mechanics Method
    Chemical Research in Chinese Universities, 2001
    Co-Authors: Jiang Ping
    Abstract:

    In this paper, the steric energies of the following molecule pairs are discussed and compared by means of the molecular mechanics method, (1) cis- and trans-: ClHgCHCHCl(Ⅰ), ClHgCHCHHgCl(Ⅱ), ClCHCHCl(Ⅲ). The energy orders are E_cis-Ⅰ E_trans-Ⅰ, E_cis-Ⅱ E_trans-Ⅱ, E_cis-Ⅲ E_trans-Ⅲ; (2) o- and m-: C_6H_4HgCl_2(Ⅳ), C_6H_4Hg_2Cl_2(Ⅴ), C_6H_4Cl_2(Ⅵ), the energy orders are E_o-Ⅳ E_m-Ⅳ, E_m-Ⅴ E_o-Ⅴ, E_o-Ⅵ E_m-Ⅵ. From the energy barriers of internal rotations of the following molecules, Cl_Hg_CH_2_CH_2_Y, Y=_CN(Ⅶ), _C_6H_5(ⅩⅠ), the energies of cis-molecules(Ⅶ, ⅩⅠ), are lower than those of trans-ones. The energies would be increased when we changed _Hg_Cl into _Cl or _CN. From above calculation, we concluded that there are Secondary Chemical Bonds in such an organo-metallic compounds as cis-Ⅰ, o-Ⅳ, Ⅶa, ⅩⅠa. The formation of Secondary Bond can decrease the molecules energies.

Lai Cheng - One of the best experts on this subject based on the ideXlab platform.

  • Theoretical Study on Secondary Bond in Organo-Metallic Compound(I)──The Conjugated Bond and Secondary Bond in β-Chlorovinyl Mercury Chloride
    Chemical Research in Chinese Universities, 1995
    Co-Authors: Lai Cheng
    Abstract:

    According to the analysis of experimantal data, we found that :(l)crystal structure indicates that the title trans-molecule has a plane structure; (2)The vector sum of Bond-moment of individual single, double and triple Bond can not be used to explain the molecular dipole moment; (3)Raman spectrum misses characteristic frequency of vibration of double or triple Bond; (4)Ultra-violet absorption λmax shifts toward red; (5) C-Cl Bond in chloroethylene molecule and C Hg Bonds in diphenyl mercury molecule are proved to be conjugated. Thus we infer there exists a conjugated Bond in the title molecule including the vacant 6pz orbital of mercury. In order to further study the formation of this conjugated Bond,we applied MNDO semi-empirical molecular orbital calculation to these cis- and transmolecules.The results show that in each molecule, there exist someπmolecular orbitals involving empty 6pz orbital of mercury atom, the C Hg Bond has about 0.1 π-Bond order,thus it proves the vacant 6pz orbital of mercury indeed participates in the formation of conjugated system.By comparison of the difference of properties of cis- with trans- compound, we found that the cis- one has a higher melting poin,more negative heat of formation and the heat of elimination of C2H2 from this molecule, less quantity in isotope exchange,its decompostion in alcohol is more slow, and its 1,4-reaction is more difficult to take place.In view of above distiction it shows that cis-molecule is more stable than trans-one. Thus we assumed that in cis-molecule there is a weak Secondary Chemical Bond which located in the plane of molecule,essentially it is a weak three centers with four electrons delocalization Bond. MNDO calculation supports this viewpoint.In , in l964, the author already predicted the existence of this Bond in abovemolecul.