Cis-3-Methyl-4-octanolide

cis-3-Methyl-4-octanolide, also called cis-β-methyl-γ-octalactone or 5-butyldihydro-4-methylfuran-2(3H)-one, is a chemical compound of the lactone family with formula C
₉H
₁₆O
₂. It exists in two optical isomers: 3R,4R ("+") and 3S,4S ("−").

cis-3-Methyl-4-octanolide

(3R,4R)-isomer
(3S,4S)-isomer
Names
Preferred IUPAC name rel-(4R,5R)-5-Butyl-4-methyloxolan-2-one
Other names Whisky lactone; Quercus lactone; cis-β-Methyl-γ-octalactone
Identifiers
CAS Number	39212-23-2 (racemate) Y 80041-00-5 (3S,4S) Y 55013-32-6 (3R,4R) Y
3D model (JSmol)	(3R,4R): Interactive image (3S,4S): Interactive image
ChemSpider	37679 (3R,4R) 9270013 (3S,4S)
PubChem CID	41285 (3R,4R) 11094871 (3S,4S)
UNII	HKX8Y5BUAO (racemate) Y DR7KRE2AJV (3S,4S) Y O93PZ85MTG (3R,4R) Y
InChI InChI=1S/C9H16O2/c1-3-4-5-8-7(2)6-9(10)11-8/h7-8H,3-6H2,1-2H3/t7-,8-/m1/s1 (3S,4S): InChI=1S/C9H16O2/c1-3-4-5-8-7(2)6-9(10)11-8/h7-8H,3-6H2,1-2H3/t7-,8-/m0/s1
SMILES (3R,4R): O=C1O[C@H](CCCC)[C@@H](C1)C (3S,4S): CCCC[C@@H]1OC(=O)C[C@@H]1C
Properties
Chemical formula	C9H16O2
Molar mass	156.225 g·mol−1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

The 3S,4S isomer, commonly known as whisky lactone or quercus lactone is an important ingredient in the aroma of whiskey (where it was first identified by Suomalainen and Nykänen in 1970) and other alcoholic beverages that have been aged in oak barrels. It is sometimes added to the liquor as a flavoring agent.^[1][2][3][4] It has a coconut, celery or fresh wood aroma, that can be detected by humans at the concentration of 1 μg/L in air.^[5] A mixture of the cis and trans isomers is repellent for mosquitos and flies.^[6]

The 3S,4S isomer is extracted by the alcoholic beverage from some precursor substances in the oak wood.^[5][7][8] It can be synthesized from a cyclopentane derivative.^[6]

See also

• trans-3-Methyl-4-octanolide, a stereoisomer also found in oak-aged beverages.

3-Methyl-4-octanolide, cis and trans isomers.