AbstractThe surface product formed in the reaction between TiCl3and Al(CH3)3has been studied. Stoichiometric data, CH3/CD3exchange, and infrared spectra permit the conclusion that the surface product is essentially a compound having the formulaA model structure is proposed for this compound, valid for the 001 face of α‐TiCl3. In it the titanium and chlorine atoms maintain the positions which they occupy in the α‐TiCl3lattice. One of the methyl groups protrudes from the surface whereas the other occupies the chlorine vacancy created during the reaction in the chlorine surface layer. A different sterism of the methyl groups is compatible with the experimental result that half of the methyl groups are very easily exchanged whereas the other half are not touched by the exchanging agent. According to this model it has to be assumed that the titanium atoms in the 001 plane, by far the largest face of the α‐TiCl3crystal, are not accessible. A similar model, loading to equivalence conclusions is proposed for β‐TiCl3. The infrared spectra of Al(CH3)3, Al(CD3)3, AlCl(CH3)2, AlCl(CD3)2, AlCl2CH3, AlCl2CD3, TiCl3CH3, TiCl3CD3, Hg(CD3)2, and Zn(CD3)2are discussed. Spectra of surface products formed on interaction of some of these compounds with TiC