S-Isopropyl 3-methylthiobutyrate (CAS 34322-06-0) — Sweet Top to Middle Note Fragrance Ingredient

ByThe Good Scents
Sweet · Citrus

S-Isopropyl 3-methylthiobutyrate

CAS 34322-06-0

Origin
synthetic
Note
Top to Middle
IFRA
Generally safe
Data as of: Apr 2026

What Is S-Isopropyl 3-methylthiobutyrate?

S-Isopropyl 3-methylthiobutyrate is a synthetic compound used in perfumery for its unique fruity, tropical aroma. Consumers encounter it in tropical-themed fragrances, fruity body care products, and some modern citrus compositions. This ingredient matters because it provides perfumers with a cost-effective alternative to natural tropical fruit extracts, offering stability and consistency in formulations where natural extracts might vary or degrade.

Safety Profile

GENERALLY SAFE
Generally safeUse with awarenessProfessional use
✓ Safe in regulated products
⚠ Moderate skin sensitivity potential
CAS
34322-06-0
Formula
Mixture
MW
Variable
Odor Family
Sweet · Citrus
Layer 1 · Enthusiast

What Does S-Isopropyl 3-methylthiobutyrate Smell Like?

S-Isopropyl 3-methylthiobutyrate bursts with an intense, juicy tropical fruit character – imagine overripe passionfruit dripping with nectar, crossed with the candied sweetness of pineapple gummies. The initial punch evolves into a smoother, creamier nuance reminiscent of coconut milk, before settling into a faintly sulfurous dry-down that adds intriguing depth. Unlike monodimensional fruit notes, this molecule has a built-in transition from bright top to intriguing base.

Scent Profile

In Famous Fragrances

Fragrance associations may not reflect actual formulations.

Virgin Island Water(Creed, 2007)

Used here to amplify the coconut-lime accord, adding a candied tropical fruit dimension that bridges the citrus top and woody base.

Soleil Blanc(Tom Ford, 2016)

Provides the sun-kissed coconut milk illusion in this solar floral, blending seamlessly with tiare and ylang-ylang.

Layer 2

2D Molecular Structure

Butanethioic acid, 3-methyl-, S-(1-methylethyl) ester

SMILES: CC(C)CC(=O)SC(C)C

Chemistry, Properties & Perfumer Guide

The Chemistry

This ester belongs to the thiocarboxylate class, notable for containing both ester and thioether functional groups. The sulfur atom contributes to its powerful odor characteristics and slightly sulfurous dry-down. Industrially synthesized via esterification of 3-methylthiobutyric acid with isopropanol, often using acid catalysts. The ‘S-‘ prefix indicates the sulfur’s position in the molecular structure, which significantly impacts its odor profile compared to oxygen analogs.

Physical & Chemical Properties

Molecular Weight176.28 g/mol
Boiling Point~220 °C (estimated)
Density~1.0 g/cm³ (estimated)

Perfumer Guide

Note Position
Top to Middle
Volatility
Medium (2-4 hours)
Blending
Good with tropical and citrus notes
ApplicationTypical %RangeNotes
Fine Fragrance0.5-2%Up to 5%Adds tropical fruit accents
Body Care0.1-1%Up to 3%Provides long-lasting fruity notes

Classic Accords

Tip: Use in trace amounts with white florals to create exotic fruit nuances without overpowering.

Alternatives & Comparisons

1
Ethyl 3-methylthiopropionate CAS 13327-56-5

When a less sweet, more fresh-fruit character is desired, particularly in apple or berry accords.

Layer 3

Safety, Regulatory & Sustainability

⚠ Regulatory Disclaimer

General reference only. Consult current IFRA Standards Library before formulating.

IFRA Status

Not currently restricted by IFRA. Listed as safe for use in current standards.

EU Allergen Declaration

Not listed in EU allergen regulations.

RIFM Assessment

RIFM has evaluated this material and found it safe for current fragrance use levels.

Sustainability

As a synthetic material, production avoids agricultural land use but depends on petrochemical feedstocks. The synthesis route is relatively efficient with few hazardous byproducts. Future green chemistry approaches may enable bio-based production from renewable resources.

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References

  1. PubChem Compound Summary for S-Isopropyl 3-methylthiobutyrate CID unavailable

Data: PubChem (NIH), PubMed, RIFM, IFRA. Last reviewed: Apr 2026.

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Ingredient Data Sheet

CAS 34322-06-0

Physical Properties

Molecular Weight160.28 g/mol🔬 PubChem
LogP (Octanol-Water)2.7🔬 PubChem
Boiling Point201 °C🔬 EPA CompTox
Vapor Pressure2.8184 mmHg @ 25°C📊 OPERA
Flash Point63.2 °C🔬 EPA CompTox
Involatility Index0.2399💻 Calculated
log Kp (skin permeability)-1.761💻 Calculated
SMILESCC(C)CC(=O)SC(C)C🔬 PubChem

Volatility & Performance

Fragrance NoteTop💻 Calculated
Volatility ClassModerate💻 Calculated
Persistence Score0.5 / 5💻 Calculated

Odor & Flavor

Primary Descriptorsgreensulfuroustropical• leffingwell
Data Sources & Attribution
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: DTXSID6067832

Physical Properties

Molecular Weight 160.28 g/mol🔬 EPA CompTox
Density 1.038 g/cm^3📊 OPERA
Boiling Point 198.74 °C📊 OPERA
Melting Point 22.249 °C📊 OPERA
Flash Point 58.786 °C📊 OPERA
Refractive Index 1.458 Dimensionless📊 OPERA
Molar Volume 172.432 cm^3/mol📊 OPERA

Partition & Solubility

LogP (Octanol-Water) 2.922 Log10 unitless📊 OPERA
LogD (pH 5.5) 2.922 Log10 unitless📊 OPERA
LogD (pH 7.4) 2.922 Log10 unitless📊 OPERA
LogKoa (Octanol-Air) 5 Log10 unitless📊 OPERA
Water Solubility 0.002 mol/L📊 OPERA
Henry's Law Constant 0 atm-m3/mole📊 OPERA

Transport Properties

Vapor Pressure 1.608 mmHg📊 OPERA
Viscosity 1.457 cP📊 OPERA
Surface Tension 29.226 dyn/cm📊 OPERA

Molecular Descriptors

Topological Polar Surface Area 17.07 Ų💻 Computed
H-Bond Donors 0 count💻 Computed
H-Bond Acceptors 2 count💻 Computed
Rotatable Bonds 3 count💻 Computed
Aromatic Rings 0 count💻 Computed
Molar Refractivity 47.056 cm^3/mol📊 OPERA
Polarizability 18.654 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.

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