Predict ¹H NMR spectra for classic organic teaching molecules.
Proton NMR spectroscopy lets chemists determine an organic molecule's structure by reading how hydrogen atoms in different chemical environments absorb radio-frequency energy differently — a technique covered in both AP Chemistry and IChO organic chemistry, and one of the most information-rich structure-determination tools available.
Chemical shift (δ, measured in parts per million) indicates a hydrogen atom's electronic environment: hydrogens near electronegative atoms or functional groups are deshielded (their electron density is pulled away) and appear farther downfield (higher δ), while hydrogens in electron-rich environments are shielded and appear upfield (lower δ). Tetramethylsilane (TMS) is universally used as the zero-point reference, since its twelve equivalent hydrogens are unusually shielded and appear far upfield of nearly everything else measured.
Characteristic shift ranges let you assign structural fragments directly from a spectrum: alkyl CH3 hydrogens typically appear around 0.9-1.5 ppm, CH2 hydrogens adjacent to a carbonyl or similar group shift further downfield to roughly 2-2.5 ppm, hydroxyl (O-H) protons appear in a broad, variable range around 3-5 ppm (their exact position shifts with concentration and hydrogen bonding), and aromatic ring hydrogens appear characteristically far downfield, around 7-8 ppm, due to the ring current effect unique to aromatic systems.
The n+1 splitting rule governs peak multiplicity: a hydrogen (or equivalent set of hydrogens) with n neighboring, chemically non-equivalent hydrogens on adjacent carbons splits into n+1 peaks — a hydrogen next to a CH3 group (3 neighbors) splits into a quartet, while a hydrogen next to a CH2 group (2 neighbors) splits into a triplet, giving direct structural information about what's connected to what.
Integration — the relative area under each peak — is directly proportional to the number of equivalent hydrogens producing that peak, letting you determine the ratio of different hydrogen environments even without knowing the molecule's total hydrogen count in advance.
This predictor generates realistic ¹H NMR spectra for classic teaching molecules like ethanol, acetone, diethyl ether, and acetic acid, showing chemical shift, splitting, and integration together as an integrated structure-determination exercise.