What a learner can do afterwards
- Relates chemical shift to the electron density around a proton and predicts the shift for a named environment
- Converts relative integrals into proton counts consistent with the molecular formula
- Applies the splitting rule to predict a pattern and reads a pattern back to a neighbour count
- Recognises exchangeable protons and explains what a deuterium oxide shake proves
1 · Read
Shift starts with structure: each functional group sets its own neighbourhood. Protons near oxygen or double bonds feel less shielding and slide downfield, while plain alkyl protons huddle upfield. When you meet a new molecule, circle the functional groups before looking at any spectrum, predict a rough shift zone for each proton set, then let the real peaks confirm or correct you.
Integration says how many protons sit behind each signal. Divide each area by the smallest one to get whole number ratios, then scale so the parts sum to the proton total from the formula. Areas of 2 to 2 to 3 with 14 protons in total mean 7 parts of 2 protons each, so the largest signal holds 6 protons. Areas of 1 to 2 to 2 with 10 protons mean 5 parts of 2, so the largest holds 4.
Splitting says how many neighbours each set has. Count the protons on the neighbouring carbons and add one: two neighbours give a triplet and three give a quartet. Read it backwards too: a quartet means three equivalent neighbours next door. Counting signals is a separate job from reading splitting. Equivalent protons share one signal, so symmetry cuts the number of signals: ethanol shows three signals, while its isomer dimethyl ether, with all six protons equivalent, shows one.
Exchangeable protons reveal themselves in a heavy water shake. OH and NH protons, and other protons on oxygen, nitrogen or sulfur, swap with deuterium and their signals vanish, since deuterium does not show in a proton spectrum. Protons on carbon do not swap. So a vanishing signal marks an exchangeable proton. Test each sketch against all three clues at once: shift must suit the environment, integrals must sum to the formula, and splitting must match neighbour counts.
Shift names the neighbourhood, integrals count the protons, splitting counts the neighbours, and the shake exposes OH and NH.
Readings 'Ethanol, signal by signal' and 'Where signals usually sit' are original to this dataset. Practice items x1, x2, x3 are original to this dataset.
2 · Watch
Take it off screen
Where it sits
11 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.