When treated with a Grubbs catalyst, compound A (under conditions of high dilution) is converted into one product (compound 1) with the molecular formula C6H8O2. Under similar conditions, compound B is converted into two products, compounds 2 and 3, each of which has the molecular formula C8H12O2. Draw the structures of compounds 1, 2, and 3 and explain why compound A gives only one metathesis product while compound B gives two metathesis products.