Possible response:

Identifying X in a Hydrocarbon with Molecular Formula C10H20

Criteria for X

To determine which of the given options satisfy the criteria of X in the hydrocarbon with molecular formula C10H20, we need to apply the principles of free radical chlorination and constitutional isomerism. Free radical chlorination involves the substitution of a hydrogen atom in a hydrocarbon by a chlorine atom via a chain reaction mechanism that generates free radicals. The number and position of the chlorine atoms in the product depend on the reactivity and selectivity of the free radicals and the nature of the substrate. Constitutional isomerism refers to the phenomenon in which two or more compounds have the same molecular formula but different connectivity or arrangement of atoms. Therefore, to obtain two constitutional isomers from the chlorination of C10H20, we need to have a hydrocarbon that has two or more different positions or types of hydrogens, such that the substitution by chlorine leads to distinct products.

Options for X

A) C2H5

If X is C2H5, then the hydrocarbon is decane (C10H20), which has 10 different types of hydrogens (9 methylene and 1 methyl). Free radical chlorination of decane can occur at any of these positions, leading to a mixture of isomeric products. However, none of these products would have the molecular formula C10H19Cl, as each substitution would decrease the number of hydrogens by one. Therefore, option A does not satisfy the criteria of X.

B) C2H4Cl

If X is C2H4Cl, then the hydrocarbon is 1-chloro-2-methylundecane (C10H19Cl), which has one chlorine atom and nine different types of hydrogens (8 methylene and 1 methyl). Free radical chlorination of this hydrocarbon can occur at any of the methylene positions, leading to a mixture of isomeric products. However, only two of these products would have the molecular formula C10H19Cl, namely 1-chloro-3-methylundecane and 1-chloro-4-methylundecane, which are constitutional isomers. Therefore, option B satisfies the criteria of X.

C) C2H3Cl2

If X is C2H3Cl2, then the hydrocarbon is 1,2-dichloro-3-methyldecane (C10H18Cl2), which has two chlorine atoms and nine different types of hydrogens (8 methylene and 1 methyl). Free radical chlorination of this hydrocarbon can occur at any of the methylene positions or at one of the methyl positions, leading to a mixture of isomeric products. However, none of these products would have the molecular formula C10H19Cl, as each substitution would decrease the number of hydrogens by one or two. Therefore, option C does not satisfy the criteria of X.

Conclusion

Based on the given information, only option B, C2H4Cl, satisfies the criteria of X in the hydrocarbon with molecular formula C10H20. Therefore, the hydrocarbon is 1-chloro-2-methylundecane, and the constitutional isomers obtained from its free radical chlorination are 1-chloro-3-methylundecane and 1-chloro-4-m