Kinetics of reaction of metal alkyl compounds with alkenes. Part 5.—Aluminium triethyl and substituted alkenes

Abstract

The kinetics of the addition reactions of aluminium triethyl with several linear, branched and cyclic alkenes have been re-studied, using dilatometry and g.1.c. product analysis. The concentration dependence of rate is consistent with the monomeric form of aluminium triethyl alone being reactive. The Arrhenius parameters are analyzed in terms of four-centre transition states for the addition react ions.Conflicting reaction mechanisms 1-6 have been proposed for the addition of aluminium triethyl to n-alkenes. In previous publications in this series l 9 it was established that the reaction was inhibited by dimerization of aluminium triethyl and that monomer alone was active in adding to the alkene. This confirmed the findings of Zeigler et aL39 Natta et aZ.,5 however, concluded that dimer was the active species while Allison et aL6 considered, from a comparison of Arrhenius parameters, that dimer participated either exclusively or in conjunction with monomer in the rate-determining step of the addition reaction. The similarity in structure between aluminium trialkyl dimers and the soluble co-ordinated anionic polymerization initiator complexes, obtained from reacting bis-cyclopentadienyl titanium dichloride and aluminium triethyl, i.e., C5H5 X C2H5\ / \ / Ti A1 / \ / \ C5H5 X C2H5 where X r C 2 H 5 or C1, has been used to infer that the addition reaction involved dimer participation alone.7A further study of this system has been made using dilatometry since initial studies with n-hexene-1 indicated that the volume change which accompanied the reaction was directly related to the reaction extent, and that the technique was less restricted than that of a constant pressure manostat, used previously with more volatile alkenes. EXPERIMENTALThe alkanes and alkenes, listed in table 1, were employed as reagents or calibrants for g.1.c. analysis. The purities listed are minimum values as determined by g.1.c. analysis. The reagents were used after drying under vacuum over activated molecular sieves (type 4A), and vacuum distillation.

Modern views on the stereospecifity of anionic active centers. Review

“…It should be noted that GENKIN [93] who investigated the R3Al-yl-donor systems by GLC established the possibility of the formation of corresponding complexes only for the non-associated forms of organoaluminium compounds ; this result support the previous assumption of HAY et al [94] who drew similar conclusion from kinetic data. It cannot be ruled out that this feature is characteristic of OLC also, being the cause of the unsuccessful attempts to detect the complexes under consideration by spectroscopy.…”

Metal complex catalysis in the synthesis of organoaluminium compounds

“…Catalytic carboalumination of unsaturated compounds gives an access to novel types of higher OAC. It is known 97 that carboalumination of terminal alkenes in the absence of catalysts usually occurs under drastic conditions and is accompanied by side reactions of hydro-and dehydroalumination. In the presence of metal complex catalysts, carboalumination proceeds under milder conditions and with higher selectivity.…”

Gas chromatography

“…The methyl-, ethyl-, and phenyl-organomercuric compounds of the RHgX type were also determined by GC using subtractive techniques (693). Organotin (117,220, SOI), -aluminum (119, 438), and -gallium (119), n-butylboronic acid derivatives of 1,2-and 1,3-diols (137), organohalogermanes (587,1032) and compounds of the type (C2H5) rM-M'-(C2H5) 3 where M and M' are Si, Ge, or Sn and form heteroelement-heteroelement bonds (118,120) were also successfully eluted.…”