Chemical Properties
clear colourless liquid
Definition
ChEBI: The tertiary alcohol arising from addition of water across the C2C double bond of citronellal.
Description
Hydroxycitronellal has an intense, sweet, floral, lily-type odor. It
may be prepared by hydration of natural citronellal obtained from
Java citronella or from Eucalyptus citriodora; P-pinene is converted to myrcene, which on hydration may yield either linalool
or a mixture of geranoil and nerol; the latter mixture can be
hydrogenated to citronellol and subsequently converted to citronellal and hydroxycitronellal; also by hydrogenation of 3,7-dimethyl-
7-hydroxy-2-octen-2-al over palladium carbon in ethyl acetate
solution.
Occurrence
Reported found in pepper
Uses
7-Hydroxycitronellal shows fungicide activity the strains of Candida tropicalis.
Uses
Hydroxycitronellal is a fragrance for use in various perfumes, antiseptics, insecticides and household products; some perfumery uses (sweet pea Pois De Senteur; gardenia; cherry; melon; mint).
Preparation
The most important synthetic routes to hydroxydihydrocitronellal
are listed as follows.
1) Synthesis from citronellal: One of the oldest routes to hydroxydihydrocitronellal
is the hydration of the citronellal bisulfite adduct (obtained at low
temperature) with sulfuric acid, followed by decomposition with sodium
carbonate. A more recent development is hydration of citronellal enamines
or imines, followed by hydrolysis.
2) Synthesis from citronellol. Citronellol is hydrated to 3,7-dimethyloctane-1,7-
diol, for example, by reaction with 60% sulfuric acid. The diol is dehydrogenated
catalytically in the vapor phase at low pressure to give highly pure
hydroxydihydrocitronellal in excellent yield.The process is carried out in the
presence of, for example, a copper–zinc catalyst; at atmospheric pressure,
noble metal catalysts can also be used.
3) Synthesis from 7-hydroxygeranyl/-neryl dialkylamine: The starting material
can be obtained by treatment of myrcene with a dialkylamine in the
presence of an alkali dialkylamide, followed by hydration with sulfuric
acid. The 7-hydroxygeranyl/-neryl dialkylamine isomerizes to the corresponding
7-hydroxyaldehyde enamine in the presence of a palladium(II)-
phosphine complex as catalyst. Hydrolysis of the enamine gives 7-hydroxydihydrocitronellal
[151].
Taste threshold values
Taste characteristics at 50 ppm: sweet, waxy, green, floral and melon notes.
Flammability and Explosibility
Notclassified
Trade name
Laurinal® (Takasago).
Synthesis
By hydration of natural citronellal obtained from Java citronella or from Eucalyptus citriodora; β-pinene is converted
to myrcene, which on hydration may yield either linalool or mixture of geranoil and nerol; the latter mixture can be hydrogenated
to citronellol and subsequently converted to citronellal and hydroxycitronellal; also by hydrogenation of 3,7-dimethyl-7-hydroxy-2-
octen-2-al over palladium carbon in ethyl acetate solution.
