Snyder polarity index table
Snyder's polarity index (P′) ranks solvents on one scale from ~0 (non-polar) to 10.2 (water), with selectivity groups (I–VIII) and eluotropic strength on silica. Sorted least to most polar.
Compiled by Hemant RawatLast reviewed July 2026How we verify
| Solvent | Polarity P′ | Selectivity group | ε° (silica) | Water |
|---|---|---|---|---|
| n-Pentane | 0 | — | 0.00 | immiscible |
| Iso-octane | 0.1 | — | 0.01 | immiscible |
| n-Heptane | 0.1 | — | 0.01 | immiscible |
| n-Hexane | 0.1 | — | 0.01 | immiscible |
| Cyclohexane | 0.2 | — | 0.03 | immiscible |
| Carbon tetrachloride | 1.6 | — | 0.11 | immiscible |
| Triethylamine | 1.9 | I | — | partial |
| Toluene | 2.4 | VII | 0.22 | immiscible |
| MTBE | 2.5 | I | 0.48 | partial |
| Benzene | 2.7 | VII | 0.25 | immiscible |
| Diethyl ether | 2.8 | I | 0.38 | partial |
| Dichloromethane | 3.1 | V | 0.30 | immiscible |
| 1,2-Dichloroethane | 3.5 | V | 0.30 | immiscible |
| 2-Propanol | 3.9 | II | 0.60 | miscible |
| n-Butanol | 3.9 | II | 0.70 | partial |
| 1-Propanol | 4 | II | 0.63 | miscible |
| n-Butyl acetate | 4 | VIa | — | immiscible |
| Tetrahydrofuran | 4 | III | 0.53 | miscible |
| Chloroform | 4.1 | VIII | 0.26 | immiscible |
| tert-Butanol | 4.1 | II | — | miscible |
| Methyl isobutyl ketone | 4.2 | VIa | — | partial |
| Ethanol | 4.3 | II | 0.88 | miscible |
| Ethyl acetate | 4.4 | VIa | 0.38 | partial |
| Methyl ethyl ketone | 4.7 | VIa | — | partial |
| 1,4-Dioxane | 4.8 | VIa | 0.49 | miscible |
| Acetone | 5.1 | VIa | 0.53 | miscible |
| Methanol | 5.1 | II | 0.73 | miscible |
| Pyridine | 5.3 | III | — | miscible |
| Acetonitrile | 5.8 | VIb | 0.52 | miscible |
| Acetic acid | 6 | IV | — | miscible |
| N,N-Dimethylformamide | 6.4 | III | — | miscible |
| N,N-Dimethylacetamide | 6.5 | III | — | miscible |
| N-Methylpyrrolidone | 6.7 | III | — | miscible |
| Dimethyl sulfoxide | 7.2 | III | — | miscible |
| Water | 10.2 | VIII | — | miscible |
What the polarity index (P′) means
The polarity index P′, introduced by L. R. Snyder, is a single number summarizing how polar a solvent is, derived from its interactions with test solutes. It runs from about0.0 for pentane up to 10.2 for water. Higher P′ means a stronger solvent in reversed-phase HPLC and a weaker one in normal-phase — the direction flips because the two modes have opposite stationary-phase polarities.
The selectivity group (I–VIII) captures how a solvent interacts (proton donor, proton acceptor, dipole) — solvents in different groups can share a P′ yet give different separations, which is the basis of the selectivity triangle. Eluotropic strength ε° ranks normal-phase eluent strength on a given adsorbent; values vary between silica and alumina and between sources, so treat them as relative.
Sources
- Stenutz / L. R. Snyder — Solvent polarity index (P′) and selectivity groups
- USP <621> — Chromatography — general chapter
- NIST — Chemistry WebBook — thermophysical properties (BP, density, refractive index)
Values are compiled from public references and were last verified July 2026. See ourmethodologyfor how we source and verify. Always confirm critical values against primary references and the SDS.