Propyl disulfide
[CAS 629-19-6]

Identification

• Classification: Flavors and spices >> Synthetic spice >> Thioether perfume
• Name: Propyl disulfide
• Synonyms: Dipropyl Disulfide; Di-n-propyl disulfide
• Molecular Formula: C₆H₁₄S₂
• Molecular Weight: 150.30
• CAS Registry Number: 629-19-6
• EC Number: 211-079-8
• FEMA: 3228
• SMILES: CCCSSCCC

Properties

• Density: 1.0±0.1 g/cm³ Calc.^*, 0.96 g/mL (Expl.)
• Melting point: -86 °C (Expl.)
• Boiling point: 190.9±9.0 °C 760 mmHg (Calc.)^*, 195 - 196 °C (Expl.)
• Flash point: 66.1 °C (Calc.)^*, 64 °C (Expl.)
• Index of refraction: 1.501 (Calc.)^*, 1.497 (Expl.)

^* Calculated using Advanced Chemistry Development (ACD/Labs) Software.

Safety Data

• Hazard Symbols: GHS07 Warning
• Risk Statements: H302-H319
• Safety Statements: P264-P264+P265-P270-P280-P301+P317-P305+P351+P338-P330-P337+P317-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Eye irritation	Eye Irrit.	2	H319
Acute toxicity	Acute Tox.	4	H302
Skin irritation	Skin Irrit.	2	H315
Specific target organ toxicity - single exposure	STOT SE	3	H335
Specific target organ toxicity - single exposure	STOT SE	3	H336
Flammable liquids	Flam. Liq.	2	H225
Chronic hazardous to the aquatic environment	Aquatic Chronic	2	H411

chemBlink Chemical Story

Propyl disulfide, CAS 629-19-6, is more precisely dipropyl disulfide, a simple organosulfur compound with the structure propyl-S-S-propyl. PubChem records the formula C6H14S2 and identifies it as a plant metabolite and a component of essential oils from Allium species. It is also described as a major pungent volatile associated with onion-like aroma.

The chemistry of onions, garlic and related plants is rich in sulfur compounds. Intact plant tissue stores relatively nonvolatile sulfur precursors, but cutting or crushing activates enzymatic chemistry that generates reactive sulfur species and a complex mixture of thiosulfinates, sulfides, disulfides and related volatiles. Dipropyl disulfide belongs to this broader family of odor-active compounds, although the exact sulfur profile varies greatly among Allium species.

Its S-S bond is central to both odor chemistry and chemical reactivity. Organic disulfides can undergo reduction to thiols, oxidation to higher sulfur-oxygen states, and exchange reactions with other sulfur species. The two propyl groups make dipropyl disulfide relatively hydrophobic; FAO/JECFA describes it as insoluble in water but soluble in ethanol and oil, with a pungent sulfur-like onion or garlic odor.

The compound also has a recognized food-flavor role. The U.S. FDA's Substances Added to Food inventory lists propyl disulfide, CAS 629-19-6, as a flavoring agent or adjuvant under 21 CFR 172.515, and gives FEMA number 3228. JECFA lists it as flavoring number 566.

Dipropyl disulfide therefore connects plant biochemistry, sensory chemistry and practical flavor formulation. A molecule containing only six carbons and two sulfur atoms can have a disproportionate sensory impact because the human nose is highly responsive to volatile sulfur compounds. Its importance is measured less by bulk quantity than by the strong odor information carried by a small concentration.

References:
1. PubChem, Dipropyl disulfide, CID 12377, CAS 629-19-6.
2. U.S. FDA, Substances Added to Food: Propyl Disulfide, CAS 629-19-6.
3. FAO/JECFA, Propyl disulfide, JECFA No. 566, FEMA 3228.
4. Block E. Garlic and Other Alliums: The Lore and the Science. Royal Society of Chemistry, 2010.

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