Terpene limonene

When a bowl containing fresh oranges is placed on the dining room table, the room acquires their fragrance within a few hours. The organic substance we smell after its release from the oranges is the organic terpene (+)-limonene (I), each molecule of which is small and relatively non-polar. I readily evaporates at room temperature to form a vapour. 

Terpenes (limonene, ce-pinene) Scented deodorizers, polishes, fabrics, fabric softeners, cigarettes, food, beverages... 

Problem 9.35 Pick out the isoprene units in the terpenes limonene, myrcene and a-pheliandrene, and in vitamin A, shown below,... 

Italian mandarin oils are characterised by the terpenes limonene (app. 70%) and y-terpinene (app. 20%). Apart from a-sinensal and long-chain saturated aldehydes there is a number of sensorially important unsaturated aldehydes with citrus-like, aldehy-dic, fatty and waxy flavour. Also the potent C-11-hydrocarbons (l,3E,5Z)-undeca-triene, (1,3E,5E,8Z)-, (l,3E,5Z,8Z)-undecatetraene and methyl N-methylanthranilate characterise the typical taste and odour of red mandarin [76]. The latter compound, which also causes the fluorescent character of mandarin oil, is a main constituent of mandarin leaf oils (see Petitgrain oils). 

Key Words Ethylene oxide, Propylene oxide. Epoxybutene, Market, Isoamylene oxide. Cyclohexene oxide. Styrene oxide, Norbornene oxide. Epichlorohydrin, Epoxy resins, Carbamazepine, Terpenes, Limonene, a-Pinene, Fatty acid epoxides, Allyl epoxides, Sharpless epoxidation. Turnover frequency, Space time yield. Hydrogen peroxide, Polyoxometallates, Phase-transfer reagents, Methyltrioxorhenium (MTO), Fluorinated acetone, Alkylmetaborate esters. Alumina, Iminium salts, Porphyrins, Jacobsen-Katsuki oxidation, Salen, Peroxoacetic acid, P450 BM-3, Escherichia coli, lodosylbenzene, Oxometallacycle, DFT, Lewis acid mechanism, Metalladioxolane, Mimoun complex, Sheldon complex, Michaelis-Menten, Schiff bases. Redox mechanism. Oxygen-rebound mechanism, Spiro structure. 2008 Elsevier B.V. 

Sometimes the abrasive is given as an optional ingredient in an otherwise completely liquid cleaning formula. In one example of this type, the abrasive is combined into a terpene/limonene solvent-based cleaner while remaining stable [45], In another example, the surfactant instead of the abrasive is largely eliminated [46],... 

Snider has found dialkyl aluminium halides to be excellent catalysts for this reaction and they can be used to stop the reaction after the first step. This is a real advance in the Prins reaction that otherwise tends to give a mixture of products by multiple addition of the aldehyde and intervention by various nucleophiles. A simple example is the addition of formaldehyde to the terpene limonene 208 catalysed by BF3. A single monoadduct 210 is formed in good yield.34 This must be a Lewis acid catalysed carbonyl ene reaction on the external double bond 209. Notice the excellent chemoselectivity in that the internal alkene is not attacked and the excellent regioselectivity in that hydrogen atoms at four other sites might have taken part in the reaction, but do not. 

Table 11.2 contains some data that exemplify the above comments. It cites values of the activity coefficient for an ester (benzyl acetate), an alcohol (heptan-2-ol) and a terpene (limonene) in different environments encompassing a range of polarities water (highly polar), an aqueous surfactant (as used in shampoos) and a moderately polar solvent used in perfumery (diethyl phthalate, DEP). It can be seen that heptanol and limonene have values of y in DEP, which are similar and also greater than that of benzyl acetate, but in water limonene has a very large activity coefficient. Limonene is not able to participate in any strong cohesive interactions with water molecules, and the high y is a consequence... 

The syntheses in Schemes 10.6,10.7, and 10.10 are stereoselective. In Scheme 10.6, the starting material is an optically active terpene, limonene. The chiral center leads to modest stereoselectivity in the hydroboration (step A), there is a 3 2 preference for the desired stereoisomer,- and the intermediate is obtained stereochemically pure after crystallization of a solid derivative. These chiral centers are not involved in any of the further transformations, so the stereochemistry is established early in the synthesis, and all further reactions are free of complications due to separation of stereoisomers. In Scheme 10.7, the stereochemistry is controlled by virtue of the bicyclic nature of the intermediate Diels-Alder adduct. The isomeric... 

These are almost universal in essential oils, acting also as precursors of the more complex, oxidised terpenes. Limonene, for example, is the precursor of the main constituents of the monoterpenes in mints, Mentha spp. (Lamiaceae), including carvone and menthol... 

Singh, P., R. Shukla, B. Prakash et al., 2010b. Chemical pro le, antifungal, antia atoxigenic and antioxidant activity of Citrus maxima Burm. and Citrus sinensis (L.) Osbeck essential oils and their cyclic mono-terpene, -limonene. FoodCjwmCTQ j., 48(6) 1734 1740. 

ISO standard 3475 shows character and data for that oil. This oil often is produced not only from the fruits but also from the whole aerial part. Values of cis- and tran -anethole are then reduced in smaller amount. Adulteration with star anise oil can be easily detected. Anise fruit oil does not contain any foeniculin, but star anise oil contains up to 3% (ISO 11016). On the other hand pseudo-isoeugenol-2-methylbutyrate is a component of anise fruit oil (0.3%-2%, ISO 3475) and does not appear in star anise oil. The midratio of cA-anethole to frani -anethole in anise seed oil in relation to star anise oil is 0.3% 0.6%. Synthetic anethole, fennel terpene limonene (80°), and terpineol were used for blending. 

FIGURE 23.12 Mechanism of the formation ofthe mono-terpene limonene from geranyl diphosphate. 

The principal difference between English and French oil of lavenda is that the former contains only a very small quantity of linalyl esters whilst cineol appears to be a normal constituent of English oil. Semmler and Tiemann have isolated from English oil the terpene limonene, linalol, and i-linalyl acetate. Cineol and a sesquiterpene are also normal constituents of the oil. 

The known constituents of the oil are the terpene, limonene, terpineol, and traces of citronellal. 

The structure of the terpene limonene is shown below (see also Exercise 5-29). Identify the two 2-methyl-l,3-butadiene (isoprene) nnits in limonene. (a) Treatment of isoprene with catalytic amonnts of acid leads to a variety of oligomeric products, one of which is limonene. Devise a detailed mechanism for the acid-catalyzed conversion of two molecules of isoprene into limonene. Take care to nse sensible intermediates in each step, (b) Two molecnles of isoprene may also be converted into fimo-nene by a completely different mechanism, which takes place in the strict absence of catalysts of any kind. Describe this mechanism. What is the name of the reaction ... 

---