This question involves identifying the major product of an electrophilic addition reaction of an alkene with HBr. The key concept here is Markovnikov's Rule.

Step 1: Analyze the Reactant
The reactant is an alkene with the structure: $C H_{3} - C H = C H_{2}$ (Propene). The double bond is between the second and third carbon atoms.

Step 2: Apply Markovnikov's Rule
Markovnikov's rule states that when a protic acid (like HBr) adds to an unsymmetrical alkene, the hydrogen atom bonds to the carbon with the greater number of hydrogen atoms. In propene, the terminal carbon (CH₂) has two hydrogens, while the internal carbon (CH) has one. Therefore, the hydrogen from HBr will add to the terminal carbon (CH₂), and the bromine will add to the more substituted carbon (the CH carbon, which is attached to a CH₃ group).

Step 3: Predict the Carbocation Intermediate
The addition proceeds via a carbocation intermediate. Adding H⁺ to the terminal carbon creates a secondary carbocation on the middle carbon: $C_{3} H_{7} B^{r}$ . This is more stable than the alternative primary carbocation.

Step 4: Form the Final Product
The bromide ion (Br^-) then attacks the positively charged carbon, forming the major product: 2-Bromopropane. $C H_{3} - C H B r - C H_{3}$

Final Answer: The major product is 2-Bromopropane, which corresponds to the structure in the second option.

Related Topics

Markovnikov's Rule: A rule in organic chemistry that predicts the regiochemistry of electrophilic addition reactions to alkenes. The electrophile adds to the carbon with the most hydrogen atoms, and the nucleophile adds to the more substituted carbon.

Carbocation Stability: The stability of carbocations follows the order: tertiary > secondary > primary > methyl. This stability influences the major product formed in addition reactions.

Formulae

While there is no specific mathematical formula, the application of Markovnikov's rule is crucial: $H - X + C = C \to - C - C - X$ (where H adds to the less substituted carbon).