Compound A, M⁺= 86, shows an IR absorption at 1730 cm^-and a very simple ¹HNMR spectrum with peaks at 9.7 $\delta$(1 H, singlet) and 1.2 $\delta$(9 H, singlet). Propose a structure for A.

It is a spectrometry that is used to determine the molecular mass of the compound and the structure by plotting the ion signal as a function of mass to charge ratio.

As per the given data, the molecular ion peak is observed at 86 so we can identify the molecular formula that must be C₅H₁₀O as per the mass to charge ratio.

As the IR peak is observed at 1730 cm^{- 1}so the compound must be aldehyde reaction a follow:

As per the NMR data is given it is observed that the peak at 9.7 is due to the single hydrogen of CH of the CHO aldehyde group which is present next to the carbonyl of the aldehyde and the other peak at 1.2 is due to the 9H that means three methyl group are present in tertiary form and all are identical so product 1 singlet all are equivalent hydrogen which is present on the left side of the carbonyl so the structure is 2,2 dimethyl propanal