¹H NMR spectroscopy explorer
See how chemical shift, integration and n + 1 splitting arise in the ¹H NMR spectra of real compounds, shake O–H and N–H protons out with D₂O and deduce the structures of unknowns.
Learning goals
- Interpret chemical shift
- Account for deuterated solvents and labile protons
- Determine proton equivalence and signal count
- Use peak integration to count protons
- Interpret first-order spin–spin splitting and multiplicity
Learning objectives
- Interpret chemical shift
- Account for deuterated solvents and labile protons
- Determine proton equivalence and signal count
- Use peak integration to count protons
- Interpret first-order spin–spin splitting and multiplicity
- Use the delta scale and TMS reference
- Explain electronegativity and inductive effects on shielding
- Explain anisotropic effects on chemical shift
Simulated ¹H NMR spectrum of ethyl ethanoate, CH₃COOCH₂CH₃: δ 4.12 quartet, step 14.8 mm; δ 2.04 singlet, step 22.2 mm; δ 1.26 triplet, step 22.2 mm. TMS is at δ 0. The cursor is at δ 4.12, on the quartet.
- Cursor, δ
- 4.12 ppm
- Signal
- quartet
- Integration step
- 14.8 mm
Try this
0 of 4 doneFind a quartet and a triplet in the same compound. (not done yet)
A CH₂ next to a CH₃ has three neighbouring H, so it splits into n + 1 = 4 lines in the ratio 1 : 3 : 3 : 1. The CH₃ has two neighbours and gives a 1 : 2 : 1 triplet.
Shake a compound that has an O–H or N–H group with D₂O. (not done yet)
O–H and N–H protons exchange with deuterium. Deuterium gives no ¹H signal, so their peak disappears and a small HOD peak appears near δ 4.7.
Select the aldehyde H of ethanal and the ring H of ethylbenzene. (not done yet)
π electrons circulating in C=O and in the benzene ring deshield the H next to them, so these signals lie far downfield, at δ 9–10 and δ 7–8.
Deduce two unknowns, then check each against the reference spectrum of your structure. (not done yet)
The number of signals gives the proton environments, the integration gives their ratio, the splitting gives the neighbours and δ gives the nearby groups.