The reaction of C4H8 (butene) with HCl (hydrochloric acid) is an addition reaction where the HCl molecule adds across the double bond in the butene molecule. This results in the formation of two possible products:

* 2-chlorobutane: This is the major product, formed when the hydrogen atom from HCl adds to the carbon atom with the most hydrogen atoms attached already (Markovnikov's rule).

* 1-chlorobutane: This is the minor product, formed when the hydrogen atom from HCl adds to the carbon atom with fewer hydrogen atoms attached.

Here's the reaction with the structural formulas:

C4H8 (butene) + HCl → CH3CH2CHClCH3 (2-chlorobutane) OR CH3CH2CH2CH2Cl (1-chlorobutane)

Key Points:

* Markovnikov's Rule: In the addition of HX (where X is a halogen) to an alkene, the hydrogen atom preferentially adds to the carbon atom that already has more hydrogen atoms attached.

* Carbocation Stability: The formation of the more stable carbocation intermediate leads to the formation of 2-chlorobutane as the major product.