The vapour pressure of aluminium triethyl is measured in the range 60-120°C, and found to obey the relationship loglop -10-85-3613/7', which gives values of 186"C, 16.5 kcal/mole of vapour and 35.9 cal/mole deg. for the boiling point, heat of vaporization and Trouton's constant. These values are anomalous and are attributed to the presence of association,The heat of association is -10.2 kcal/mole of A.l,Et,. This value is used to evaluate the Arrhenius parameters of the reaction of aluminium triethyl monomer and a-alkenes.Alkyl aluminium compounds are associated species, but the extent of association depends strongly on the nature of the alkyl group. Aluminium n-alkyls are dimeric,l while aluminium tri-(iso-propyl) and tri-(j so-butyl) are monomeric. 1-3 Aluminium di(alky1) hydrides are trimeric.2Electron diffraction studies have established that the electron deficient aluminium tri-n-alkyl dimers have a boron hydride structure with bridging alkyl groups, i.e.,
n-Butyl-lithium (BuLi) in the presence of NNN'N'-tetramethylethylenediamine (TMEDA ) progressively adds on ethylene molecules to produce a linear alkyl-lithium compound. This oligomerization has been studied at low pressure, 0-2 atmosphere, and temperature, 270-310 K, and hydrocarbons, up to Cls0, have been isolated on hydrolysis. The rate of consumption of ethylene depends on the pressure and BuLi concentration but is independent of TMEDA concentration. No addition of ethylene, however, occurs in the absence of TMEDA or in the presence of simple tertiary amines under the conditions used. The molecular weights of the hydrolyzed reaction products increase with the mol of ethylene consumed and their distributions (Mw/Mn) are Poisson, indicating the absence of any transfer or termination steps. A mechanism for the addition reaction is proposed.
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