a. What is the relative abstraction of H and D ? b.Why free-radical chlorination of CH_(4) is nearly 11 times faster than CD_(4) ?

a. What is the relative abstraction of H and D ? b.Why free-radical

1.	a. What is the relative abstraction of H and D ? b.Why free-radical chlorination of CH_(4) is nearly 11 times faster than CD_(4) ?
Answer» SOLUTION :a.i.Number of H atoms abstracted by D =5 and PERCENTAGE of compound formed `=93%` .Therefore, REACTIVITY factor for replacement of H atoms `=93//5 =18.6` ii.Number of D abstracted by C1 = 1 and percentage of compound formed `=7%`.Therefore, relative factor for D replacement `=7//1 =7` iii. Relative reactivity of H : Dabstraction `=18.6//7 =2.7 : 1`, i.e., each H is abstracted `2.7` times FASTER than D. b.Chemically, H and D are identicsl but (C ----D) bonds are slightly stronger than (C----H) bonds,therefore, the energy of activation of D is greater than that of H. Since abstraction is a slow STEP, removal of H will be faster. Relative abstraction of `H : D = 2.7 : 1` Relative abstractionof `4H : D ~~ 10.8 : 1` `~~ 11 : 1`