Grapefruit mercaptan is a natural

organic compound Some chemical authorities define an organic compound as a chemical compound that contains a carbon–hydrogen or carbon–carbon bond; others consider an organic compound to be any chemical compound that contains carbon. For example, carbon-co ...

found in

grapefruit The grapefruit (''Citrus'' × ''paradisi'') is a subtropical citrus tree known for its relatively large, sour to semi-sweet, somewhat bitter fruit. The flesh of the fruit is segmented and varies in color from pale yellow to dark red. Grapefru ...

. It is a monoterpenoid that contains a

thiol In organic chemistry, a thiol (; ), or thiol derivative, is any organosulfur compound of the form , where R represents an alkyl or other organic substituent. The functional group itself is referred to as either a thiol group or a sulfhydryl grou ...

(also known as a mercaptan)

functional group In organic chemistry, a functional group is any substituent or moiety (chemistry), moiety in a molecule that causes the molecule's characteristic chemical reactions. The same functional group will undergo the same or similar chemical reactions r ...

. Structurally a

hydroxy group In chemistry, a hydroxy or hydroxyl group is a functional group with the chemical formula and composed of one oxygen atom covalently bonded to one hydrogen atom. In organic chemistry, alcohols and carboxylic acids contain one or more hydroxy ...

terpineol Terpineol is any of four isomeric monoterpenoids. Terpenoids are terpene that are modified by the addition of a functional group, in this case, an alcohol. Terpineols have been isolated from a variety of sources such as cardamom, cajuput oil, ...

is replaced by the thiol in grapefruit mercaptan, so it also called thioterpineol. Volatile thiols typically have very strong, often

unpleasant odor An odor (American English) or odour (English in the Commonwealth of Nations, Commonwealth English; American and British English spelling differences#-our, -or, see spelling differences) is a smell or a scent caused by one or more volatilized ...

s 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. Pure grapefruit mercaptan, or citrus-derived oils rich in grapefruit mercaptan, are sometimes used in

perfumery Perfume (, ) is a mixture of fragrance, fragrant essential oils or aroma compounds (fragrances), Fixative (perfumery), fixatives and solvents, usually in liquid form, used to give the human body, animals, food, objects, and living-spaces an agre ...

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.{{cite journal , author=Demole, E. , author2=Enggist, P. , author3=Ohloff, G. , year = 1982 , title = 1-p-Menthene-8-thiol: A powerful flavor impact constituent of grapefruit juice (Citrus parodisi MACFAYDEN) , journal = Helvetica Chimica Acta , volume = 65 , issue = 6 , pages = 1785–1794 , doi = 10.1002/hlca.19820650614

References

Thiols Flavors Perfume ingredients Monoterpenes Cyclohexenes

See also

References