tert-Butanol
Properties
| State | Solid/Liquid (colorless, waxy crystals; mp 25.5°C; camphor-like odor) |
| Color | Colorless |
| Solubility | Miscible with water; miscible with ethanol, ether, and most organic solvents |
| Melting Point | 25.5°C |
| Boiling Point | 82.4°C |
About tert-Butanol
tert-Butanol — (CH3)3COH, 74.122 g/mol — is the oddball of the C4 alcohol family because it's a waxy solid at typical lab room temperatures (mp 25.5°C). On a winter morning the bottle is a single block of crystals and you're reaching for the heat gun; on a July afternoon it's a clear liquid sloshing around. The high melting point comes from the molecule's nearly spherical, compact shape — three methyl groups arranged tetrahedrally around the C-OH carbon pack into the crystal lattice with unusual efficiency, beating out the elongated n-butanol, sec-butanol, and isobutanol isomers (all liquids well below 0°C). The functional consequence of being a tertiary alcohol matters more in synthesis: there's no α-hydrogen on the carbon bearing the hydroxyl, so PCC, Jones reagent, KMnO4, and Swern oxidation all leave it untouched. That makes tert-butanol the cosolvent of choice when you need an alcohol that won't get oxidized along with the substrate — Sharpless asymmetric dihydroxylation is the classic example, where t-BuOH/water is the standard solvent system. The tert-butyl group also turns up everywhere in protecting-group chemistry: tert-butyl ethers, tert-butyl esters, and (most importantly) the Boc protecting group for amines that runs through every peptide synthesis and a large fraction of pharmaceutical process chemistry.
Where you'll encounter it
If you've ever run a Boc deprotection with TFA in dichloromethane and watched the gentle bubbling as CO2 evolves, you've seen tert-butanol generated transiently — it's the leaving piece when the Boc group falls off an amine. Synthetic chemists at Merck, Pfizer, and every contract-manufacturing organization use ton-scale tert-butanol in solvent mixtures for asymmetric dihydroxylation of alkenes (Sharpless AD-mix). On the industrial side, tert-butanol is the upstream feedstock for MTBE — methyl tert-butyl ether, the gasoline octane booster that was phased out in the U.S. after 2005 because of groundwater contamination concerns but is still produced at multi-million-tonne scale globally. The other place chemists run into it is as a denaturant in laboratory-grade ethanol — adding a few percent tert-butanol makes the ethanol non-potable for tax purposes but doesn't interfere with most synthetic uses.
Common Uses
- Cosolvent for Sharpless asymmetric dihydroxylation (t-BuOH/water with AD-mix)
- Source of tert-butyl ether, tert-butyl ester, and Boc protecting groups in synthesis
- Solvent for oxidation reactions where solvent oxidation must be avoided
- Industrial feedstock for MTBE octane booster production
- Denaturant in laboratory-grade ethanol (along with methanol and isopropanol)
- Methyl methacrylate (Plexiglas precursor) intermediate via dehydration to isobutylene
- Teaching example for tertiary alcohol reactivity, SN1 mechanism, and E1 elimination
Safety Information
GHS: Flammable Liquid Category 2 (H225, flash point 11°C closed cup), Acute Toxicity Category 4 (oral, H302), Eye Irritation Category 2A (H319), STOT-SE Category 3 (H335 respiratory, H336 narcotic). Occupational exposure limits are comparatively permissive, and the regulatory and advisory values coincide. Less hepatotoxic than methanol, more sedating than ethanol. Causes drowsiness and dizziness on inhalation, similar to short-chain ether anesthesia. NTP listed as a possible carcinogen based on rat kidney tumor evidence, though the relevance to humans is debated. Stored bottles should be checked for peroxide formation if exposed to air for long periods, though peroxide accumulation is much slower than for THF or diethyl ether. Treat as a flammable liquid even when solid — the solid sublimes and the vapor still flashes at room temperature.
This safety summary is for educational reference only and may not be complete. It is not a substitute for Safety Data Sheets (SDS), medical advice, or professional chemical safety guidance. Always consult appropriate SDS and qualified professionals before handling chemicals. We deliberately do not publish occupational exposure limits or other regulatory thresholds: those values are revised over time and differ between jurisdictions, so the only correct source is the current SDS and the regulations that apply where you work.