Grapefruit Mercaptan

It is a monoterpenoid that contains a thiol (also known as a mercaptan) functional group. Structurally a hydroxy group of terpineol is replaced by the thiol in grapefruit mercaptan, so it also called thioterpineol. Volatile thiols typically have very strong, often unpleasant odors that can be detected by humans in very low concentrations. Grapefruit mercaptan has a very potent, but not unpleasant, odor, and it is the chemical constituent primarily responsible for the aroma of grapefruit. This characteristic aroma is a property of only the R enantiomer.

Grapefruit mercaptan

Names
Preferred IUPAC name 2-[(1R)-4-Methylcyclohex-3-en-1-yl]propane-2-thiol
Other names grapefruit mercaptan 1-p-menthene-8-thiol α,α,4-trimethylcyclohex-3-ene-1-methane thiol thioterpineol
Identifiers
CAS Number	71159-90-5 (racemate) Y 83150-78-1 (R enantiomer) N
3D model (JSmol)	Interactive image
ChemSpider	21163535 Y
ECHA InfoCard	100.072.886
EC Number	275-223-1
PubChem CID	6427135
UNII	7AT54D0N8R Y
CompTox Dashboard (EPA)	DTXSID00894921
InChI InChI=1S/C10H18S/c1-8-4-6-9(7-5-8)10(2,3)11/h4,9,11H,5-7H2,1-3H3/t9-/m0/s1 N Key: ZQPCOAKGRYBBMR-VIFPVBQESA-N N InChI=1/C10H18S/c1-8-4-6-9(7-5-8)10(2,3)11/h4,9,11H,5-7H2,1-3H3/t9-/m0/s1 Key: ZQPCOAKGRYBBMR-VIFPVBQEBF
SMILES SC(C)(C)[C@@H]1CCC(C)=CC1
Properties
Chemical formula	C10H18S
Molar mass	170.31 g/mol
Density	1.03 g/cm3
Melting point	< 25 °C (77 °F; 298 K)
Boiling point	58 °C (136 °F; 331 K) at .33 mmHg
Hazards
GHS labelling:
Pictograms
Signal word	Warning
Hazard statements	H302, H315, H319
Precautionary statements	P264, P270, P280, P301+P312, P302+P352, P305+P351+P338, P321, P330, P332+P313, P337+P313, P362, P501
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

Pure grapefruit mercaptan, or citrus-derived oils rich in grapefruit mercaptan, are sometimes used in perfumery and the flavor industry to impart citrus aromas and flavors. However, both industries actively seek substitutes for grapefruit mercaptans for use as a grapefruit flavorant, since its decomposition products are often highly disagreeable to the human sense of smell.

The detection threshold for the (+)-(R) enantiomer of grapefruit mercaptan is 2×10⁻⁵ ppb, or equivalently a concentration of 2×10⁻¹⁴. This corresponds to being able to detect 2×10⁻⁵ mg in one metric ton of water - one of the lowest detection thresholds ever recorded for a naturally occurring compound.

• Nootkatone, another aroma compound in grapefruit
• Terpineol, where a hydroxyl is in place of the thiol