2-Butene and 1-Butene?

Question

When 2-butene reacts with hydrogen chlorine gas, only one product is detected, whereas when 1-butene reacts similarly, two products are usually found. Explain this.

Answer 1

2-butene is symmetrical: CH2CH=CHCH3 so no matter to which C of the double bond the Cl attaches the product is the same (2-chloro-butane).

1-butene is not:
CH3CH2CH=CH2 so Cl can go either to C-1 and the H to C-2 giving CH3CH2CH2CH2-Cl or
Cl can go to C-2 and H to C-1 giving
CH3CH2CH-CH3
.. .. .. .. .. . l
.. .. .. .. .. .Cl

In practice you use Markovikov's rule to find out which is the main product (here it is the 2-chlorobutane)

Answer 2

The product with both is 2-chlorobutane, I'm afraid. This is an optically active molecule, so two products are obtained.