The major product of the following reaction sequence is a mixture of isobutylene and isopentane. The reason for this is that the hydrogenation of alkenes involves the addition of hydrogen to the double bond, causing the double bond to break and form two single bonds. In this case, the double bond in the alkene is located between carbon atoms 1 and 2, so when the hydrogenation reaction occurs, isobutylene (C4H8) and isopentane (C5H12) are formed as the major products, along with small amounts of other products such as cyclohexane and pentane due to side reactions.
To understand why the major products are isobutylene and isopentane instead of butane and pentane, it is important to consider the reactant molecules and the products that are formed. In the reaction sequence, an alkene (an organic compound with at least one double bond) reacts with hydrogen gas. The double bond in the alkene is polarized, meaning that the electrons are drawn towards the more electronegative atom of the double bond. When the hydrogenation reaction occurs, the hydrogen atoms add to the carbon atoms that are surrounded by the double bond, forming new covalent bonds.
Since the carbon atoms in the alkene have a double bond, they have a unique structure with alternating single and double bonds. When the hydrogenation reaction occurs, the hydrogen atoms add to the carbon atoms that are part of the double bond, resulting in the formation of isobutylene (C4H8) and isopentane (C5H12). These substances have similar molecular weights but differ in their molecular weights by one carbon atom, resulting in the formation of a mixture of isobutylene and isopentane as the major products.
It is also important to note that the formation of these products is not solely dependent on the reactant molecules but also on the conditions of the reaction, such as the pressure,temperature, and concentration of the reactants. In this case, the use of efficient catalysts and high pressure can increase the rate of the reaction and favor the production of isobutylene and isopentane as the major products.