3-Methyl-2-butene-1-thiol: Aroma, Smell and Safety | PatientsCann UK

3-Methyl-2-butene-1-thiol

prenylthiol, prenyl thiol, VSC3

pronounced: three-METH-il two-BYOO-teen one-THY-ol

The number one skunk molecule. The main reason strong cannabis smells the way it does.

Skunk & dieselFormula: C5H10SExtremely potent
Aroma family
Skunk
Formula
C5H10S
Mass
102.20 g/mol
Main note
Skunky

3-Methyl-2-butene-1-thiol · 102.20 g/mol

The molecule

Chemical structure

This is the accurate skeletal structure of 3-Methyl-2-butene-1-thiol, drawn from PubChem data. Each corner and line-end is a carbon atom. The yellow S marks sulphur, the atom that gives this whole family its powerful smell.

SkunkyGassySulphurousPungent

About

What is 3-Methyl-2-butene-1-thiol?

3-Methyl-2-butene-1-thiol is the molecule most responsible for the strong, skunky smell people link with cannabis. It is often called prenylthiol. In 2021 a research team led by Iain Oswald pinpointed it as the number one skunk odorant in the plant.

It carries a small chemical part called a prenyl group. This same building block turns up all over the cannabis plant, which may be why the smell feels so specific to cannabis.

What the research says

The Science

Using a very sensitive method (two-dimensional gas chromatography with sulphur detection), the team measured this compound across many cultivars. The more of it a plant had, the more strongly people rated its skunky smell.

It is powerful in tiny amounts. Even at a few parts per billion the nose picks it up easily, which is why a little goes a very long way.

Aroma snapshot

How 3-Methyl-2-butene-1-thiol Smells

Skunk & diesel family
SkunkyGassySulphurousPungent
Smell strength: Extremely potent

Detectable at just a few parts per billion. A tiny trace can fill a room.

You might also smell it in: Skunk spray, and beer that has been left in the light (so-called "lightstruck" beer).

Its role in the smell

Part of the Whole

On its own it smells purely skunky. Mixed with the fruity and piney terpenes, it helps give each cultivar its signature aroma. It sits alongside terpenes and cannabinoids as part of the plant's full character.

Good to know

A Note on Safety

3-Methyl-2-butene-1-thiol is an aroma compound, present in cannabis in trace amounts. It is not a medicine and has no dose of its own. What matters for you is the whole product and how it is prescribed.

Always choose and adjust your medicine with your prescriber and pharmacist, never by smell alone.

Questions

3-Methyl-2-butene-1-thiol: Common Questions

Is this what makes cannabis smell skunky?
Yes. Research from 2021 found that 3-methyl-2-butene-1-thiol is the main molecule behind the classic skunky smell. The more a plant makes, the skunkier it tends to smell.
Is it related to skunk spray or garlic?
It belongs to the same broad family as the smelly molecules in skunk spray and garlic, called volatile sulphur compounds. That shared family is why all three can smell so strong.
Back to full Sulphur Compounds Guide
Important: This page is for education only. It is not medical advice. Research into cannabis sulphur compounds is very new, and most work so far is about smell, not treatment. The garlic comparison is about chemistry, not proven health effects. Always speak to your prescriber before changing your treatment. PatientsCann UK does not recommend any specific cannabis product.

References

  1. Oswald, I.W.H., Ojeda, M.A., Pobanz, R.J., Koby, K.A., Buchanan, A.J., Del Rosso, J., Guzman, M.A. and Martin, T.J. (2021) 'Identification of a new family of prenylated volatile sulfur compounds in cannabis revealed by comprehensive two-dimensional gas chromatography', ACS Omega, 6(47), pp. 31667-31676. doi: 10.1021/acsomega.1c04196.
  2. Russo, E.B. (2011) 'Taming THC: potential cannabis synergy and phytocannabinoid-terpenoid entourage effects', British Journal of Pharmacology, 163(7), pp. 1344-1364. doi: 10.1111/j.1476-5381.2011.01238.x.
  3. National Center for Biotechnology Information (2025) PubChem Compound Database. Bethesda: U.S. National Library of Medicine. Available at: https://pubchem.ncbi.nlm.nih.gov (Accessed: 3 August 2026).