NMR Spectroscopy

What does NMR stand for?

Nuclear Magnetic Resonance.

What type of nuclei are used in NMR?

Nuclei with an odd number of protons or neutrons (e.g. ¹H, ¹³C) that can spin.

What happens to nuclei in a magnetic field in NMR?

They align with or against the magnetic field and can absorb radio frequency radiation.

What is chemical shift?

A measure of how much the resonance frequency of a nucleus differs from a reference standard, measured in ppm.

What is the reference standard used in NMR?

Tetramethylsilane (TMS).

Why is TMS used?

It produces a single sharp peak at 0 ppm and is chemically inert.

Why do different environments give different chemical shifts?

Because electron density (shielding) around nuclei varies depending on neighbouring atoms.

What does shielding mean in NMR?

Electrons around a nucleus reduce the effect of the external magnetic field.

What is deshielding?

When electron density is reduced, exposing the nucleus more to the magnetic field, increasing chemical shift.

What information does a ¹³C NMR spectrum give?

Number of carbon environments and their chemical shifts. :contentReference[oaicite:2]{index=2}

What does the number of peaks in a ¹³C NMR spectrum show?

The number of different carbon environments. :contentReference[oaicite:3]{index=3}

What do chemical shift values in ¹³C NMR show?

The type of carbon environment present. :contentReference[oaicite:4]{index=4}

What is the typical chemical shift range for ¹³C NMR?

0–200 ppm.

What does a ¹H NMR spectrum show?

Number of proton environments, chemical shifts, integration and splitting patterns. :contentReference[oaicite:5]{index=5}

What does the number of peaks in ¹H NMR show?

The number of different proton environments. :contentReference[oaicite:6]{index=6}

What does the area under a peak (integration) show?

The relative number of protons in each environment.

What does splitting (spin-spin coupling) show?

The number of neighbouring non-equivalent protons.

What is the n+1 rule?

A peak is split into n+1 peaks where n is the number of neighbouring hydrogens.

What is a singlet?

A peak with no splitting (no neighbouring hydrogens).

What is a doublet?

A peak split into two (one neighbouring hydrogen).

What is a triplet?

A peak split into three (two neighbouring hydrogens).

Why are deuterated solvents used in NMR?

They do not produce peaks in the spectrum because deuterium does not interfere. :contentReference[oaicite:7]{index=7}

Give an example of a deuterated solvent.

CDCl₃ or D₂O. :contentReference[oaicite:8]{index=8}

How can NMR be used to determine structure?

By analysing number of peaks, chemical shifts, integration ratios and splitting patterns together. :contentReference[oaicite:9]{index=9}

What does a downfield shift mean?

Higher ppm value, more deshielded nucleus.

What does an upfield shift mean?

Lower ppm value, more shielded nucleus.