Compounds A and B are two hydrocarbons with the molecular formula C9H14 which, by treatment with one mole of HCl, can each give rise to two monochlorinated derivatives of different constitution and which, in catalytic reduction, absorb 2 moles of hydrogen. Compound A, by ozonolysis followed by reducing treatment leads to methanal and 3,5-dimethyl-2-oxohexanedial, while B leads to 5-methyl-2-oxoheptanedial. Deduce the constitution of compounds A and B knowing that A gives the Diels Alder reaction with Z-butenedioic acid anhydride, while B cannot give it.