Grapefruit mercaptan

Grapefruit mercaptan is the common name for a natural organic compound found in grapefruit. 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.[1] This characteristic aroma is a property of only the R enantiomer.[2]

Grapefruit mercaptan
Grapefruit mercaptan
Grapefruit mercaptan
Grapefruit mercaptan
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
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.072.886
EC Number
  • 275-223-1
UNII
  • 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
  • SC(C)(C)[C@@H]1CCC(C)=CC1
Properties
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:
GHS07: Exclamation mark
Warning
H302, H315, H319
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).
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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.[3]

See also

References
  1. Buettner A.; Schieberle P. (1999). "Characterization of the Most Odor-Active Volatiles in Fresh, Hand-Squeezed Juice of Grapefruit (Citrus paradisi Macfayden)". J. Agric. Food Chem. 47 (12): 5189–5193. doi:10.1021/jf990071l. PMID 10606593.
  2. Lehmann D.; Dietrich A.; Hener U.; Mosandl A. (1994). "Stereoisomeric flavor compounds. LXX: 1-p-menthene-8-thiol: separation and sensory evaluation of the enantiomers by enantioselective gas chromatography-olfactometry". Phytochemical Analysis. 6 (5): 255–257. doi:10.1002/pca.2800060506.
  3. Demole, E.; Enggist, P.; Ohloff, G. (1982). "1-p-Menthene-8-thiol: A powerful flavor impact constituent of grapefruit juice (Citrus parodisi MACFAYDEN)". Helvetica Chimica Acta. 65 (6): 1785–1794. doi:10.1002/hlca.19820650614.
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