3.2.10 (HL)—¹H NMR spectroscopy
- Syllabus
- First assessment 2025
- Objective
- 3.2.10
- Level
- HL
¹H NMR Evidence
HL only| NMR feature | Information |
|---|---|
| Number of signals | Number of hydrogen environments |
| Chemical shift | Environment type |
| Integration | Relative number of hydrogens in each environment |
Use all three features together to constrain the structure; do not infer the whole molecule from one signal alone.
Ethanol gives three proton environments with an expected integration ratio 3:2:1 for CH₃, CH₂ and OH, though the OH shift can vary. Normalize integrations to a whole-number ratio and match shifts to environments before assembling fragments; signal count alone is insufficient.
Protons share one signal only when they are chemically equivalent in the molecular environment; use symmetry or a substitution test rather than visual closeness. Integration gives relative signal area, so normalize ratios rather than treating raw values as absolute proton counts. Chemical-shift ranges can overlap, so use shift together with integration, signal count and structure.
Using ¹H NMR to Deduce Structure
HL onlyAssessment in practice
Representative question
Question 1
[Maximum number: 4]
Deduce the features of a high-resolution 1HNMR spectrum of ethanol, including the number of signals, their expected chemical shifts, integration traces and the splitting patterns.
Number of signals:
Chemical shift (ppm) range of each signal:
Integration traces:
Splitting pattern expected:
Number of signals: 3
Chemical shift (ppm) range of each signal:
0.9-1.0 «ppm»
AND
3.3-3.7 «ppm»
AND
1.0-6.0 «ppm»
Integration traces:
3 AND 2 AND 1
Splitting pattern expected:
triplet/3
AND
quartet/quadruplet/4 / multiplet
AND
«broad» singlet/1/triplet/3
Marking guidance:
Accept the chemical shifts and splitting patterns in any order.
Accept "3,4 and 1" for the splitting pattern, in any order.
Accept any three correct answers for a single signal for [1] each.
Organic Analysis Summary
Retrieve the route: translate formulae, identify functional groups and series, name and classify isomers, then use mass, IR, and NMR evidence together to determine structure.
Check connectivity, functional-group evidence, formula/mass constraint, shifts and integration, splitting neighbours, and agreement across every technique.