2-Methylundecanal has a characteristic fatty odor assuming a floral
note on dilution. It has an acrid, fatty unpleasant flavor at high
levels. At low levels, the flavor is honey- and nut-like. It may be
prepared by cracking the corresponding glycidic acid; from
α-nonyl acrolein; from methyl nonyl ketone and ethyl monochloroacetate
in the presence of sodium ethylate.
clear colourless to yellowish liquid
2-Methylundecanal has a characteristic fatty odor assuming a floral note on dilution. At high levels, it has an acrid, fatty,
unpleasant flavor. At low levels, the flavor is honey and nut-like.
Reported found in kumquat peel oil.
2-Methylundecanal is reported as being
found in nature. It is a colorless liquid, with an odor markedly different from that
of the isomeric dodecanal. It has a fatty odor with incense and ambergris notes.
2-Methylundecanal is produced by two routes:
1) 2-Undecanone is converted into its glycidate by reaction with an alkyl
chloroacetate. Saponification of the glycidate, followed by decarboxylation,
yields 2-methylundecanal.
2) The second synthesis is based on the conversion of undecanal into 2-
methyleneundecanal by reaction with formaldehyde in the presence of
catalytic amounts of amines. Hydrogenation of 2-methyleneundecanal
yields methylnonylacetaldehyde (MNA). A convenient process starts
from 1-decene: hydroformylation gives a mixture consisting mainly of
undecanal and 2-methyldecanal. Reaction of the crude product with
formaldehyde in the presence of dibutylamine yields a mixture containing
over 50% 2-methyleneundecanal. After hydrogenation of the double bond,
pure 2-methylundecanal is separated from the by-products by fractional
distillation.
In comparison with other fatty aldehydes, 2-methylundecanal is used in perfumery
in rather large amounts to impart conifer notes, particularly fir impressions,
but frequently also in fantasy compositions.
Taste characteristics at 2 ppm: waxy, fatty, metallic with a citrus nuance.
Flammability and Explosibility
Non flammable
Low toxicity by
ingestion and skin contact. When heated to
decomposition it emits acrid smoke and
irritating fumes.
By cracking the corresponding glycidic acid; from α-nonyl acrolein; from methyl nonyl ketone and ethyl monochloroacetate in the presence of sodium ethylate
See monograph on aldehyde C-8*.
