Final answer:
Compound A has a functional group that can be substituted, while Compound B has a functional group that can undergo elimination.
Step-by-step explanation:
Compound A and compound B are constitutional isomers with molecular formula C3H7Cl. When compound A is treated with sodium methoxide, a substitution reaction predominates. When compound B is treated with sodium methoxide, an elimination reaction predominates.
To propose structures A and B, we need to consider that isomers have the same molecular formula but different structures. In compound A, the substitution reaction predominates, which suggests that compound A has a functional group that can be substituted. One possible structure for compound A is 1-chloropropane:
CH3CH2CH2Cl
In compound B, the elimination reaction predominates, which suggests that compound B has a functional group that can undergo elimination. One possible structure for compound B is 2-chloropropane:
CH3CHClCH3