Explain why tetramethylsilane (TMS) is used as a standard in NMR spectroscopy.

An unknown compound, $\mathrm{X}$, of molecular formula, ${\mathrm{C}}_3{\mathrm{H}}_6{\mathrm{O}}_2$ , has the following $\mathrm{IR}$ and ${}^1\mathrm{H} \mathrm{NMR}$ spectra.

The MS of X showed peaks at $\frac{\mathrm{m}}{\mathrm{z}}$ values $= 74, 45$, and $29$(other peaks were also found). Deduce the structure of $\mathrm{X}$ using the information given and any other additional information. For each spectrum assign as much spectroscopic information as possible, based on the structure of $\mathrm{X}$.

Describe the operating principles of a UV-vis spectrometer.

What are the number of signals in ${}^1\mathrm{H} \mathrm{NMR}$ in the given molecules?

An unknown compound, $\mathrm{Y}$, of molecular formula, ${\mathrm{C}}_5{\mathrm{H}}_{10}{\mathrm{O}}_2$ , has the following $\mathrm{IR}$ and ${}^1\mathrm{H} \mathrm{NMR}$ spectra.

The MS of $\mathrm{Y}$ showed peaks at $\frac{\mathrm{m}}{\mathrm{z}}$ values $= 102, 57$(other peaks were also found). Deduce the structure of $\mathrm{Y}$ using the information given and any other additional information. For each spectrum assign as much spectroscopic information as possible, based on the structure of $\mathrm{Y}$.

The actual MS spectrum of propanal is as following.

Can you explain the peaks on the MS of propanal greater than $\frac{\mathrm{m}}{\mathrm{z}} = 58 ?$