Quick questions on Proton and carbon-13 NMR explained: HSC Chemistry Module 8

$^{13}C$ NMR is run proton-decoupled as standard, which collapses all couplings and gives a singlet for each unique carbon environment. The spectrum tells you two things:

Each unique proton environment gives one signal. Symmetry can make two formally different protons equivalent. For example, all three protons in $CH_3$ are equivalent.

Tells you the electronic environment of the proton.

The area under each signal is proportional to the number of equivalent protons in that environment. The spectrometer reports areas as a step trace; the ratio of step heights gives the proton ratio. Integration is what distinguishes a methyl (3H) from a methylene (2H) at similar chemical shift.

Spin-spin coupling to neighbouring protons splits each signal into a multiplet. The rule:

Non-destructive (sample is recovered after analysis), enormously information-rich, distinguishes isomers that IR and mass spectrometry cannot (e.g. propan-1-ol vs propan-2-ol from chemical shift and multiplicity patterns).

Needs tens of milligrams of dissolved sample (compared to nanograms for mass spec). $^{13}C$ has poor sensitivity due to 1.1% natural abundance. Solvent peaks (and water from $-OH$) can obscure regions of the spectrum.

State the four pieces of structural information that a proton NMR spectrum provides. [4 marks]

A compound with molecular formula $C_3H_6O$ shows two proton signals: a singlet (6 H) at 2.1 ppm. The carbon-13 NMR shows two signals at 30 and 207 ppm. Identify the compound and justify.

A compound $C_2H_6O$ shows two proton signals: a triplet (3 H) at 1.2 ppm and a quartet (2 H) at 3.7 ppm, plus a broad singlet (1 H) at 2.6 ppm that exchanges with $D_2O$. (a) Identify the compound. (b) Justify the multiplicity of the triplet and quartet.