4-Methoxy-2-methyl-2-butanethiol (CAS 94087-83-9) — Sweet Top to heart Note Fragrance Ingredient
4-Methoxy-2-methyl-2-butanethiol
CAS 94087-83-9
What Is 4-Methoxy-2-methyl-2-butanethiol?
4-Methoxy-2-methyl-2-butanethiol is a synthetic fragrance ingredient primarily used in perfumery to add unique sulfurous and fruity nuances. It’s found in niche fragrances and some personal care products. This molecule matters because it contributes distinctive tropical and exotic notes that are difficult to achieve with natural materials alone, allowing perfumers to create innovative scent profiles.
Safety Profile
USE WITH AWARENESSWhat Does 4-Methoxy-2-methyl-2-butanethiol Smell Like?
This sulfur-containing compound delivers an arresting duality: initial pungent, almost skanky sulfur notes rapidly transform into a surprisingly pleasant tropical fruit basket. Imagine overripe passionfruit meeting freshly cut guava, with an underlying meaty depth reminiscent of durian. The top note has a volatile, almost rubbery quality that settles into a sweet, musky heart with facets of blackcurrant and pink grapefruit. In drydown, it leaves a faintly metallic, mineralic trace that works exceptionally well in modern chypre and fruity-floral compositions.
In Famous Fragrances
Fragrance associations may not reflect actual formulations.
Used as the ‘astronaut’ note in this conceptual fragrance, providing metallic-fruity facets that evoke the smell of space stations as described by astronauts.
Contributes to the controversial bodily fluid accord, adding sweaty, tropical fruit nuances to the challenging composition.
2D Molecular Structure
SMILES: COCCC(C)(C)S
Chemistry, Properties & Perfumer Guide
The Chemistry
4-Methoxy-2-methyl-2-butanethiol belongs to the class of sulfur-containing mercaptans, specifically a methoxylated thiobutanol. While not found in nature, it shares structural similarities with tropical fruit thiols. Synthesis typically involves nucleophilic substitution of methoxy groups onto pre-formed thiol intermediates. The molecule’s chirality at the 2-position creates potential for distinct enantiomeric odor profiles, though most commercial material is racemic. Its volatility stems from the relatively small molecular weight and polar thiol group, while the methoxy group provides some stabilization.
Physical & Chemical Properties
| Appearance | Colorless to pale yellow liquid |
|---|---|
| Odor Threshold | Extremely low (ppb range) |
Perfumer Guide
| Application | Typical % | Range | Notes |
|---|---|---|---|
| Fine Fragrance | 0.01-0.1% | Up to 0.5% | Powerful modifier – use sparingly |
| Functional Products | Not recommended | Trace only | Potential for off-notes at higher concentrations |
Classic Accords
Tip: Always pre-dilute to 1% or lower before incorporating into blends due to extreme potency.
Alternatives & Comparisons
Less sulfurous alternative with similar tropical fruit character but better stability in alkaline formulations.
Cyclic sulfur compound offering more controlled release of tropical notes without initial harshness.
Safety, Regulatory & Sustainability
⚠ Regulatory Disclaimer
General reference only. Consult current IFRA Standards Library before formulating.
IFRA Status
Not currently restricted by IFRA standards, but recommended usage levels should be carefully monitored due to potency.
GHS Classification
RIFM Assessment
Under review by RIFM – preliminary data suggests low systemic toxicity but potential for local irritation at high concentrations.
Sustainability
As a synthetic material, production requires petrochemical feedstocks but avoids agricultural land use. Modern synthesis routes have improved atom economy compared to earlier methods. The extreme potency means very small quantities are needed, reducing overall environmental burden per kilogram of finished product.
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References
- Brenna et al. (2012). Structure-Odor Relationships in Mercaptans. Journal of Agricultural and Food Chemistry. ACS Publication
Data: PubChem (NIH), PubMed, RIFM, IFRA. Last reviewed: Apr 2026.
Report a data errorIngredient Data Sheet
CAS 94087-83-9Physical Properties
| Molecular Weight | 134.24 g/mol🔬 PubChem |
| LogP (Octanol-Water) | 1.3🔬 PubChem |
| Boiling Point | 159 °C🔬 EPA CompTox |
| log Kp (skin permeability) | -2.596💻 Calculated |
| SMILES | CC(C)(CCOC)S🔬 PubChem |
Volatility & Performance
| Fragrance Note | Heart💻 Calculated |
Odor & Flavor
| Primary Descriptors | sulfurous• leffingwell |
| Functional Groups | etherthiol💻 RDKit |
| 4-Methoxy-2-methyl-2-butanethiol has a black-currant-like flavor.📖 Fenaroli | |
Sensory Thresholds
| Odor Detection Threshold | 0.7154 ppm (n=14)📖 van Gemert |
Physical data: PubChem (NIH/NLM), U.S. EPA CompTox Dashboard, EPA OPERA models, RDKit. Odor & flavor: Arctander (Perfume & Flavor Chemicals), Fenaroli's Handbook of Flavor Ingredients, Leffingwell. Thresholds: van Gemert (Compilations of Odour Threshold Values). Regulatory: IFRA Standards 51st, FEMA GRAS. Trade names: Surburg (Common Fragrance & Flavor Materials). All data compiled and cross-referenced for perfumertools.com.
Physicochemical Properties
DTXSID: DTXSID9052634
Physical Properties
| Molecular Weight | 134.24 g/mol🔬 EPA CompTox |
| Density | 0.895 g/cm^3📊 OPERA |
| Boiling Point | 159.5 °C🔬 EPA CTX |
| Melting Point | -89.679 °C📊 OPERA |
| Flash Point | 42.09 °C📊 OPERA |
| Refractive Index | 1.446 Dimensionless📊 OPERA |
| Molar Volume | 148.035 cm^3/mol📊 OPERA |
Partition & Solubility
| LogP (Octanol-Water) | 2.126 Log10 unitless📊 OPERA |
| LogD (pH 5.5) | 0.716 Log10 unitless📊 OPERA |
| LogD (pH 7.4) | 1.641 Log10 unitless📊 OPERA |
| LogKoa (Octanol-Air) | 3.91 Log10 unitless📊 OPERA |
| Water Solubility | 0.102 mol/L📊 OPERA |
| Henry's Law Constant | 0 atm-m3/mole📊 OPERA |
Transport Properties
| Vapor Pressure | 3.603 mmHg📊 OPERA |
| Viscosity | 0.93 cP📊 OPERA |
| Surface Tension | 25.705 dyn/cm📊 OPERA |
Molecular Descriptors
| Topological Polar Surface Area | 9.23 Ų💻 Computed |
| H-Bond Donors | 1 count💻 Computed |
| H-Bond Acceptors | 2 count💻 Computed |
| Rotatable Bonds | 3 count💻 Computed |
| Aromatic Rings | 0 count💻 Computed |
| Molar Refractivity | 39.453 cm^3/mol📊 OPERA |
| Polarizability | 15.641 Å^3📊 OPERA |
Data Sources:
🔬 EPA Experimental data from U.S. EPA CompTox Chemicals Dashboard & CTX APIs. 📊 OPERA Predicted using EPA's OPERA QSAR models. 💻 Computed Calculated from SMILES using RDKit.
