Influence of alkene structure on the formation constants of alkene–ICl molecular complexes

The experimentally determined rate law for the addition of ICl to 22 alkenes in CCl 4 at 25 °C under conditions of (alkene) 0 [Formula: see text] (ICl) 0 is −d(ICl)/dt = k exp (alkene) 0 (ICl) 3 /{1 + C 2 (alkene) 0 } 3 . The constant C 2 is shown to be equal to K app which is a measure of the formation constant or constants of the molecular complexes in this system. Under the experimental conditions used, C 2 is a good approximation of the formation constant of the 1:1 alkene–ICl molecular complex. Thus the values of C 2 obtained allow an estimate of the effect of alkene structure on the formation constant of the first molecular complex involved in this addition reaction. The contribution of the effect of substituents on C 2 is estimated to be approximately 24% of the overall change in rate due to change in the alkene structure.