Number Of Halogen Atoms Research Articles

117Sn,119Sn–proton long-range coupling constants in the1H nuclear magnetic resonance spectra of alkylhalogenostannanes

1 H N.m.r. spectra of methyl- and ethyl-halogenostannanes have been recorded in [2H]chloroform and [2H6] dimethyl sulphoxide and the parameters obtained by accurate analysis. Large differences in the 1H parameters in the two solvents are found, especially for di- and tri-halogeno-derivatives. Long-range Sn–H coupling constants increase with electronegativity and with the number of halogen atoms, and correlations similar to those obtained for J(13C–H) can be determined for these coupling constants. The spectra for dimethyl sulphoxide solutions and the comparison with those for CDCl3 of methylhalogenostannanes provide information about the s-orbital distribution of tin in the Sn–C bonds, it being assumed that the Fermi contact mechanism is the main contribution to longrange tin–proton coupling constants, known geometries of complexes between methyltin halides and sulphoxide being used. In the case of ethyltin derivatives complications arise from the anomalous coupling constants of tin with α-protons which seem very sensitive to the nature of the groups linked to tin.

Untersuchungen zur reaktivität organometallischer komplexe III. Über die reaktion von dicyclopentadienylkobalt mit halogenmethanen

The reaction of dicyclopentadienylcobalt, Co(C 5H 5) 2, with halomethanes RX forms 1- exo-organyl derivatives of cyclopentadienylcyclopentadienecobalt where the organyl R is a halomethyl group with one, two or three halogen atoms. The reaction rate strongly depends on X and increases in the order Cl, Br, I; it also increases with the number of halogen atoms in the halomethyl group R. Derivatives with R = CH 2Cl, CH 2Br, CH 2I, CHBr 2 and the dinuclear derivative with R =- CF 2- are described for the First time. For the dichloromethyl compound (R = CHCl 2) a new and convenient synthesis is reported.

Synthesis and properties of?-haloallyl compounds of mercury

1. Β-Haloallyl derivatives of mercury with the general structure CX2=CYCH2HgZ, where X=H or Cl, or Br, and Z is a halogen atom or anα-C10H7 radical were synthesized. 2. The thermal stability of the compounds synthesized increased with the number of halogen atoms in the molecule.

Degree of polymerization and chain transfer in methyl methacrylate

The chain-transfer constants of twenty-six solvents in the polymerization of methyl methacrylate have been calculated, using Mayo’s equation for chain-transfer reaction, from the measured values of degree of polymerization of the product formed in these solvents at different concentrations at 80° C. The increase in transfer constants in hydrocarbons, alcohols, ketones, acids and ester may be effectively accounted for by the the increased polarization of the C-H bond at the α-position, by adjacent electron-attracting groups. In the case of chloro-compounds the activity has been found to depend not on the number of halogen atoms in the molecule as was suggested by Mayo but on the extent of C-Cl bond forces. Further, it is shown that simple chain transfer reactions with solvents cannot fully account for all the observed discrepancies in the kinetic measurements in solution.