2-METHYLUNDECANAL

Description

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.

Chemical properties

clear colourless to yellowish liquid

Chemical properties

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.

Occurrence

Reported found in kumquat peel oil.

The Uses of 2-METHYLUNDECANAL

Perfumery, flavoring.

Preparation

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 threshold values

Taste characteristics at 2 ppm: waxy, fatty, metallic with a citrus nuance.

Flammability and Explosibility

Non flammable

Safety Profile

Low toxicity by ingestion and skin contact. When heated to decomposition it emits acrid smoke and irritating fumes.

Synthesis

By cracking the corresponding glycidic acid; from α-nonyl acrolein; from methyl nonyl ketone and ethyl monochloroacetate in the presence of sodium ethylate

Metabolism

See monograph on aldehyde C-8*.