In additions of hydrogen

FIGURE 10 8 Energy dia gram showing relationship of kinetic control to thermo dynamic control in addition of hydrogen bromide to 1 3 butadiene... 

Boron trifluoride has been applied as catalyst in addition of hydrogen fluoride to asymmetrically halogenated alkenes in the liquid phase.52... 

Markownikoff rule In the addition of hydrogen halides to unsymmetrically constituted (unsaturated) hydrocarbons, the halogen atom becomes attached to the carbon bearing the lesser number of hydrogen atoms. Originally formulated by Markownikoff (Markovnikov) to generalize the orientation in additions of hydrogen halides to simple alkenes, this rule... 

Under certain circumstances antl-Markovnlkoff behaviour occurs, in which the opposite effect is found. This happens when the mechanism involves free radicals and is common in addition of hydrogen bromide when peroxides are present. 

The regioselectivity in addition of hydrogen halides to alkenes results from the difference in the transition state energies of two competing reactions. We recall that, according to Hammond s postulate, the structure of a transition state resembles that of an intermediate with similar energy (Section 3.17). 

---