Improvements in or related to organic compounds The invention relates to flavour or fragrance compositions containing 6-fluoro-alkenes, in particular substituted 6-fluoro-2, 6-heptadienals and to methods of flavouring or of adding fragrance to a food, beverage or a consumer product or household product using these compounds.

The flavour and fragrance industry is continuously interested in new ingredients that may impart to a product a green, lemony and citral-like character.

3, 7-dimethyl-2, 6-octadienal, well known as citral, a mixture of neral and geranial, is an important ingredient in the flavour industry and has found use in flavour compositions to impart citrus notes. However, the use of citral in the flavour industry is limited to products that do not have a low pH value, because of its instability under such conditions whereupon it degrades into aromatic ring systems, e. g. p-cresol, p-cymene and p-methylaceto-phenone, described for example by Schieberle et al. (Lebensm. - Wiss. u-Technol., 21, 158-162, 1988). These degradation products are responsible for undesirable off-notes in food products that lead to the reduction of the flavour quality. neral geranial Surprisingly, we have now found that substituted 6-fluoro-2, 6-heptadienals are very stable under acidic conditions, e. g. under conditions wherein the pH value is below 7, in particular below 4, particularly below 3. In addition these compounds show similar organoleptic properties as citral.

Accordingly, the invention provides in one of its aspects a flavour or fragrance composition comprising a compound of formula I

I wherein R, R and R3 are independently hydrogen, methyl, or ethyl.

Particularly preferred are compositions according to the invention comprise 6-fluoro-3, 7, dimethyl-2, 6-octadienal (i. e. R', R2 and R3 = methyl).

Accordingly, compounds of formula I may find use in particular in acidic flavour and fragrance applications to achieve a constant flavour quality over a long period of time, e. g. up to 10 days, more preferably up to 100 days, without degrading into undesirable off-notes.

The compounds of formula I may contain one or more prochiral centres and as such may exist as a mixture of cis-trans-isomers, or they may be resolved as isomerically pure forms. Resolving stereoisomers adds to the complexity of manufacture and purification of these compounds and so it is preferred to use the compounds as mixtures of their stereoisomers simply for economic reasons. However, if desired to prepare individual stereoisomers, this may be achieved according to methodology known in the art, e. g. column chromatography.

In a further aspect the present invention refers to food products comprising a compound of formula 1. Particular preferred are acidic food products such as beverages, e. g. carbonated soft drinks and juice drinks, such as lemon juice, orange juice or lime juice.

In a food product, a compound of formula I may be present in amounts ranging from 0.001 to 100 ppm, more preferably from 0.01 to 10 ppm, most preferred 0.1 to 7 ppm. A compound of formula I or a mixture thereof may be added to a food product alone or by adding a flavour or fragrance composition comprising a compound of formula I to a food product. The compounds of formula I are particularly well suited in flavour or fragrance

compositions where enhancement of citrus notes are required, such as lemon, orange and lime compositions.

In a further aspect the present invention refers to fragrance applications, e. g. any field of fine and functional perfumery, such as perfumes, household products, laundry products, body care products and cosmetics, comprising a compound of formula I or in combination with other known odourant molecules selected from the extensive range of natural and synthetic molecules currently available, such as essential oil, alcohols, aldehydes and ketones, ether and acetals, ester and lactones, macrocycles and heterocycles, and/or admixtures with one or more ingredients or excipients conventionally used in conjunction with odourants in fragrance compositions, for example carrier materials, and other auxiliary agents commonly used in the art.

In fragrance applications compounds of the present invention may be present in amounts ranging from 0.001 to 20 weight percent depending upon the specific application and on the nature and quantity of other odourant ingredients.

6-fluoro-2, 6-heptadienals may be synthesised starting from an appropriate fluorinated ester by Claisen rearrangement followed by Cope rearrangement, as described for example by F. Camps et al., Tetrahedron Vol. 44, No. 16, pp. 5161-5167,1988. The resulting fluorinated acid may then be reduced to the corresponding fluorinated alcohol in the presence of LiAIH4, which may further converted to the corresponding fluorinated aldehyde in the presence of Mn02, as described for example by C. Arbonés et al., Heterocycles, Vol. 31, No. 1, pp 67-78,1990.

The following example is set forth to illustrate the invention. This example is illustrative only and is not intended to limit the scope of the invention in any way.

Example 1: The acid stability of 6-fluoro-3, 7-dimethyl-2, 6-octadienal (6-F-citral) is tested in direct comparison to citral. 200 ppm solutions of 6-F-citral and citral in an acid (pH 2. 8) beverage base is made. The solutions is stored at room temperature in the dark for 111 days. Time points are analyzed by Fast-GC using an internal standard to quantify the amounts of each compound. Within 20 days, all of the citral is degraded. In

contrast, no degradation of 6-F-citral is detected. Even after 111 days, 6-F-citral is just about 100 % intact, accordingly no degradation of 6-F-citral occurs.

It should be understood that the embodiments of the present invention shown and described in the specification are only preferred embodiments of the inventors who are skilled in the art and are not limiting in any way. Therefore, various changes, modifications or alterations to these embodiments may be made or resorted to without departing from the spirit of the invention and the scope of the following claims.