Advanced Topic 822 of 1102 Organic Chemistry
Thiols
Sulfur analogs of alcohols with strong odors.
In-depth explanation of Thiols
Thiols, R-SH, are the sulfur analogues of alcohols and have similar structures, but sulfur is larger and less electronegative than oxygen. Thiols are therefore more acidic than alcohols, and the thiolate anion they form is a better nucleophile. They have powerful, unpleasant odours, and low-molecular-weight thiols are detectable at very small concentrations. Thiols oxidize readily to disulfides, R-S-S-R, which form cross-links in proteins, for example between cysteine residues.
Going deeper: Thiols
Key ideas: Thiols (R-SH) are sulfur analogues of alcohols, more acidic (pKa about 10 for ethanethiol versus 16) because the S-H bond is weaker and the larger anion is stabilised. Weaker hydrogen bonding makes boiling points lower than alcohols (ethanethiol 35 C, ethanol 78 C). Thiolates are excellent nucleophiles, and mild oxidation gives disulfides (R-S-S-R), a reversible link important in protein structure. Strong smell, used as gas odorants.
Common mistakes and connections: Students predict thiols hydrogen bond as strongly as alcohols or assume thiolates are poorer nucleophiles than alkoxides; they are better. Another mistake is oxidising thiols with strong agents to sulfonic acids when mild oxidants give disulfides. Links to cysteine, protein folding and heavy-metal binding.
Visualization of Thiols
Thiols boil lower than analogous alcohols because S-H bonds hydrogen bond only weakly, even though sulfur is larger. The interactive lesson shows this as a live animation or chart.
Worked example and use case
Garlic and skunk spray contain volatile thiols that give them their strong smells.
Frequently asked questions about Thiols
What is Thiols?
Sulfur analogs of alcohols with strong odors.
Is Thiols a beginner, intermediate or advanced topic?
Thiols is a advanced topic in Organic Chemistry. It builds on beginner and intermediate topics, so review those first if needed.
What should I learn before Thiols?
Study these earlier topics in Organic Chemistry first: Hofmann Degradation, Nitro Compounds, Nitriles.
What comes after Thiols?
The next topics in Organic Chemistry are Carbohydrate Structure and Glucose Ring Forms.
Can I practise Thiols with quizzes?
Yes. The interactive lesson includes a self-check question on Thiols, and the Organic Chemistry quiz draws on every topic in this area.
Where Thiols fits in Organic Chemistry
Thiols is topic 94 of 148 in Organic Chemistry.