The rates of alkaline solvolysis of the Si-H bond of trisubstituted silanes of the type RC6H4 (CH3hSiH, where R= m-CF3, p-Cl, p-CH3, H, p-CH30, pN (CH3) z and (CHZ= CH) n (C2HSh_nSiH (n= 0-3), have been measured. From the observed linear dependence of the logarithm of the rate constant on the aO substituent constants it follows that the d"-p,, conjugation of the phenyl group with the reaction centre produces no important effect on ...