The major product should be
2-chloro 2-methyl butane.

Reason : presence of tertiary carbon free radicle on 2nd position of straight chain.

Reaction of iso-pentane with chlorine in the presence of sunlight

When iso-pentane (also known as 2-methylbutane) reacts with chlorine in the presence of sunlight, a substitution reaction known as free radical halogenation occurs. This reaction leads to the formation of several products, including 1-chloro-2-methylbutane, 2-chloro-2-methylbutane, and 2-chloro-3-methylbutane. However, the major product obtained depends on the reaction conditions and the relative stability of the resulting free radicals.

Formation of free radicals
Initially, the chlorine molecule (Cl2) undergoes homolytic cleavage upon exposure to sunlight, resulting in the generation of chlorine free radicals (Cl•). Similarly, iso-pentane also undergoes homolytic cleavage, forming iso-pentyl free radicals (•CH(CH3)CH2CH3). These free radicals are highly reactive species and play a crucial role in the subsequent steps of the reaction.

Chain initiation
In the presence of sunlight, the chlorine free radicals act as initiators by abstracting a hydrogen atom from iso-pentane to form an iso-pentyl radical. This step leads to the formation of hydrogen chloride (HCl) as a byproduct.

Chain propagation
The iso-pentyl radical can react with a chlorine molecule, resulting in the formation of 1-chloro-2-methylbutane. This reaction involves the abstraction of a hydrogen atom from the iso-pentyl radical by a chlorine free radical, followed by the formation of a new carbon-chlorine bond. The chlorine radical generated in this step can further react with iso-pentane to produce more iso-pentyl radicals, thereby propagating the reaction.

Alternatively, the iso-pentyl radical can react with another chlorine molecule, leading to the formation of 2-chloro-2-methylbutane. This reaction also involves the abstraction of a hydrogen atom from the iso-pentyl radical, followed by the formation of a carbon-chlorine bond. Again, the chlorine radical generated can participate in further reactions, sustaining the chain propagation.

Chain termination
Chain termination occurs when two free radicals combine to form a stable molecule, effectively terminating the radical chain reaction. This can happen when two iso-pentyl radicals combine to form pentane or when an iso-pentyl radical combines with a chlorine radical to produce a chlorinated product.

Major product
The major product obtained from the reaction of iso-pentane with chlorine in the presence of sunlight is typically 2-chloro-2-methylbutane. This is because the iso-pentyl radical is more stable than the primary radical formed during the reaction, making it more likely to react with chlorine to form 2-chloro-2-methylbutane. However, the exact ratio of the products can vary depending on the reaction conditions and the presence of any other reactants or impurities.