NATURAL AND SYNTHETIC, POPULAR AND WEIRD / sweet · woody · smoky
Guaiacol
Category
NATURAL AND SYNTHETIC, POPULAR AND WEIRD
Subcategory
sweet · woody · smoky
Origin
Volatility
Base Note
Botanical
Found in Guaiacum officinale wood tar; also in smoke, coffee, and many natural sources
Appearance
Colorless to pale yellow oily liquid, solidifying at 28–32°C
Odor Strength
High
Producing Countries
Manufactured worldwide (synthetic). Natural sources: South America (guaiacum wood), ubiquitous in wood smoke globally.
Pyramid
Base
The smell of smoke distilled to a single molecule. Guaiacol is creosote without the soot, smoked meat without the meat — a clean, phenolic burn with a vanillic shadow lurking underneath.
Phenolic, smoky, and medicinal at first impact — the specific smell of creosote rather than charcoal. Warmer and more resinous than burnt wood, with none of the acrid eye-sting of actual soot. A vanillic sweetness sits underneath the phenol, subtle but persistent — a family resemblance to vanillin (its chemical cousin, one formyl group away). At low concentration: smoked ham, hearth embers, black tea dried over pine. At high concentration: antiseptic gauze, dental clinic, iodine. Compared to cade oil (which contains guaiacol among hundreds of other pyrolysis products), pure guaiacol is cleaner and more focused — the smoky signal without the noise.
Evolution over time
Immediately
Immediately
Sharp phenolic bite — creosote, iodine, smoked ham. The methoxyphenol ring hits fast and hard. Medicinal if concentrated.
After a few hours
After a few hours
Phenolic edge recedes. Warm, resinous smoke emerges with a vanillic sweetness — the structural kinship with vanillin becomes audible. Spicy-clove warmth from the methoxy group.
After a few days
After a few days
Persistent smoky-woody residue. Dry, clean, faintly sweet. Substantivity is extreme — TGSC reports 280 hours at full concentration. On a smelling strip, the trace reads as quiet hearth ash.
The Molecule — Manufacturers & Variants
Indicative 2025 wholesale prices.
The Full Story
Guaiacol (2-methoxyphenol, CAS 90-05-1, MW 124.14) is the molecule most directly responsible for the smell of wood smoke. It forms during the thermal decomposition of lignin — the structural polymer of wood — when the methoxy-substituted phenolic units of coniferyl alcohol break apart under heat. Every campfire, barbecue pit, and whiskey barrel char releases guaiacol into the air. It also occurs naturally in coffee, clove bud oil, and guaiac wood resin.
Scent Character
The odor is phenolic, smoky, and spicy-warm, with a distinct vanillic undertone — unsurprising given that guaiacol is structurally one step away from vanillin (both are methoxyphenols). At trace concentration it reads as comforting hearth-smoke and cured ham. At higher doses it turns medicinal, antiseptic, creosote-harsh. The odor threshold in water is approximately 0.48 ppb — extraordinarily low, meaning the human nose detects it at concentrations measured in parts per trillion. TGSC classifies its odor strength as High and recommends smelling in 1% solution or less.
Industrial Significance
Beyond perfumery, guaiacol is the starting material for approximately 85% of the world's synthetic vanillin production. The Rhodia process (commercialized in the 1970s) condenses guaiacol with glyoxylic acid, then oxidizes and decarboxylates the intermediate to yield vanillin. Guaiacol is also the parent compound of guaifenesin (glyceryl guaiacolate), the active ingredient in Mucinex and most over-the-counter expectorants — a direct pharmaceutical descendant of 19th-century creosote medicine.
Perfumery Use
In fine fragrance, guaiacol is dosed at 0.1–2% of the concentrate. It anchors leather accords alongside birch tar, Safraleine, and castoreum synthetics. It adds authentic smoke character to tobacco, fireside, and incense compositions. The IFRA guideline recommends a maximum of 0.5% in the fragrance concentrate. The margin between artful smoke and cough syrup is narrow — precision matters.
Every Mucinex tablet traces its chemistry back to guaiacol. Guaifenesin — the only FDA-approved over-the-counter expectorant in the United States — is glyceryl guaiacolate, a direct ether derivative of guaiacol. The pharmaceutical lineage runs deep: in the 1880s, Hermann Sahli proposed pure guaiacol as a cleaner alternative to crude creosote for treating tuberculosis, arguing it was the active compound with 'a less unpleasant taste.' The molecule went from TB wards to cough syrup to the perfumer's organ.
Extraction & Chemistry
Extraction method: Guaiacol is produced industrially by O-methylation of catechol (pyrocatechol) using dimethyl sulfate or methanol as the methylating agent. It also occurs naturally in wood tar — specifically from the pyrolysis of lignin — and can be isolated from the distillation of guaiacum resin (Guaiacum officinale). First isolated by Otto Unverdorben in 1826 from guaiac resin distillation. MW 124.14 g/mol. Melting point 28–32°C; boiling point 205–206°C. The compound is a colorless to pale yellow oily liquid at room temperature, solidifying just below 30°C. Soluble in alcohol, slightly soluble in water (7,226 mg/L at 25°C).
Found in Guaiacum officinale wood tar; also in smoke, coffee, and many natural sources
IFRA Status
IFRA recommends up to 0.5% in the fragrance concentrate. Classified as skin irritant (Category 2, H315) and eye irritant (Category 2A, H319). Acute oral toxicity Category 4 (LD50 oral-rat: 520–725 mg/kg). FEMA GRAS 2532.
Synonyms
2-METHOXYPHENOL · GUAIACOLE
Physical Properties
Odor Strength
High
Lasting Power
280 hours at 100.00%
Appearance
Colorless to pale yellow oily liquid, solidifying at 28–32°C
Boiling Point
205.00 to 206.00 °C. @ 760.00 mm Hg
Flash Point
180.00 °F. TCC ( 82.22 °C. )
Specific Gravity
1.12300 to 1.13000 @ 25.00 °C.
Refractive Index
1.53300 to 1.54400 @ 20.00 °C.
Melting Point
28.00 to 32.00 °C. @ 760.00 mm Hg
In Perfumery
Heart-to-base modifier used at trace concentrations (0.1–2% of concentrate) for authentic smoke effects. Guaiacol provides the phenolic backbone of leather (cuir) accords, where it works alongside birch tar, Safraleine, Suederal, and castoreum synthetics. It sharpens tobacco accords, adds campfire realism to incense compositions, and introduces a smoky edge to coffee and whiskey reconstructions. The molecule's substantivity is strong — TGSC reports 280 hours at 100% concentration — but its intensity demands restraint. At 0.5% it reads as atmospheric smoke; at 2% it overwhelms. In functional perfumery (soaps, candles, cleaning products) higher doses are tolerated.
