Markovnikov's Rule?

Question

Markovnikov's rule is:
"when an unsymmetrical alkene reacts with a hydrogen halide to give an alkyl halide, the hydrogen adds to the carbon that has the greater number of hydrogen substituents, and the halogen to the carbon have the fewer number of hydrogen substituents"
My question is in Markovnikov's Rule :
1)why unsymmetrical alkene is used?
2)why hydrogen halide and alkile halide is used?

Answer 1

Well, I'm not a chemist, but I'll take a stab at it:

A symmetrical alkene probably also undergoes a similar reaction, but there is no preference for one end of the molecule or another, since the ends will be identical. If it happens at all, the ends where the hydrogen and halide end up are completely random (though it's not as though you'd know, since it was symmetrical...)

I'm guessing the hydrogen halide is used because of its relative reactivity -- you're dealing with simpler organic reactions, rather than, say, rare earth or transition metal reactions. A hydrogen halide is a simple, fairly strong critter (all are strong acids, dissociating completely in solution), so the hydrogen and halide ions are free to react with anything they come across.

I could be wrong, but it seems to make sense.

Answer 2

I agree with the answer above, to the 1st question. As far as the 2nd question is concerned, hydrogen halide or alkile halide are used because in case of symple halogens the problem does not exist, since the two groups added are identical. Of course the same rule is applied when reacting with water and other substances that react with alkenes and have H or alkile as an adding part

Answer 3

1) to get alkyl halides with odd no. of carbon atoms
2)well when hydrogen halide is added to an unsymmetrical alkene, the hydrogen gets attached to one of the carbnon atoms and the halide gets attached to another...givin us an alkyl halide as the final product..

Hope its clear...