Solvent · polar protic
tert-Butanol C4H10O
Also: t-BuOH, 2-methyl-2-propanol
A polar protic alcohol used in HPLC/GC as a mobile-phase modifier and co-solvent rather than a primary eluent, because its melting point (~25-26 C) means it is solid at ambient temperature and it is highly viscous, requiring the solvent and lines to be kept warm. Uses: gradient/organic modifier and sample-solubilizing co-solvent in RP-HPLC, ion-pair and normal-phase applications, and a common co-solvent/structuring agent for lyophilization (freeze-drying) of pharmaceuticals. In GC it is both a sample solvent and an analyte of interest: tert-butyl alcohol is itself an ICH Q3C residual solvent routinely quantified by headspace GC-FID/MS. Audience: pharma/CRO residual-solvent and formulation labs.
Compiled by Hemant RawatLast reviewed July 2026How we verify
Properties
- Formula
- C4H10O
- CAS number
- 75-65-0
- UV cutoff
- 245 nm
- Snyder polarity index (P′)
- 4.1
- Selectivity group
- II
- Eluotropic strength ε° (silica)
- —
- Boiling point
- 82.4 °C
- Viscosity (25 °C)
- 4.3 cP
- Refractive index (nD²⁰)
- 1.3878
- Density
- 0.775 g/mL
- Water miscibility
- miscible
- USP <467> class
- Class 2
Safety
- flammable (GHS Flam. Liq. 2, flash point ~11 C)
- acute toxicity via inhalation (GHS Acute Tox. 4)
- eye irritant (Eye Irrit. 2)
- CNS/narcotic effects - drowsiness/dizziness (STOT SE 3)
- animal carcinogen: kidney tumors in male rats, thyroid tumors in mice (NTP); not classified as a human carcinogen
- NOT a peroxide former (tertiary alcohol, not an ether)
- solid at/below ~25 C - handling caveat (must be warmed to liquefy)
Reference only. Solvents can be flammable, toxic, or peroxide-forming. Always consult the Safety Data Sheet (SDS) and your lab's protocols before handling.
What tert-Butanol mixes with
Miscible with: 1-Propanol, 1,2-Dichloroethane, 1,4-Dioxane, 2-Propanol, Acetic acid, Acetone, Acetonitrile, Benzene, Carbon tetrachloride, Chloroform, Cyclohexane, Dichloromethane, Diethyl ether, Dimethyl sulfoxide, Ethanol, Ethyl acetate, Iso-octane, Methanol, Methyl ethyl ketone, Methyl isobutyl ketone, MTBE, n-Butanol, n-Butyl acetate, n-Heptane, n-Hexane, N-Methylpyrrolidone, n-Pentane, N,N-Dimethylacetamide, N,N-Dimethylformamide, Pyridine, Tetrahydrofuran, Toluene, Triethylamine, Water.
Check any specific pair on the interactive miscibility chart.
Using tert-Butanol in HPLC/GC
A polar protic alcohol used in HPLC/GC as a mobile-phase modifier and co-solvent rather than a primary eluent, because its melting point (~25-26 C) means it is solid at ambient temperature and it is highly viscous, requiring the solvent and lines to be kept warm. Uses: gradient/organic modifier and sample-solubilizing co-solvent in RP-HPLC, ion-pair and normal-phase applications, and a common co-solvent/structuring agent for lyophilization (freeze-drying) of pharmaceuticals. In GC it is both a sample solvent and an analyte of interest: tert-butyl alcohol is itself an ICH Q3C residual solvent routinely quantified by headspace GC-FID/MS. Audience: pharma/CRO residual-solvent and formulation labs.
Its Snyder polarity index is 4.1 (selectivity group II), and its UV cutoff of 245 nm limits low-wavelength UV detection.See what the polarity index means and the full UV cutoff table.
Sources
- University of Toronto (TRACES) — Burdick & Jackson — Solvent UV cutoff table (absorbance = 1 AU, 1 cm cell)
- Stenutz / L. R. Snyder — Solvent polarity index (P′) and selectivity groups
- NIST — Chemistry WebBook — thermophysical properties (BP, density, refractive index)
- PubChem (NIH/NLM) — Compound property records (physical constants, CAS, formula)
- USP <467> / ICH Q3C — Residual Solvents — solvent classification (Class 1/2/3)
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.
Related solvents
Other selectivity group II to compare with tert-Butanol.