Of carvones

As a further application of the reaction, the conversion of an endocyclic double bond to an c.xo-methylene is possible[382]. The epoxidation of an cWo-alkene followed by diethylaluminum amide-mediated isomerization affords the allylic alcohol 583 with an exo double bond[383]. The hydroxy group is eliminated selectively by Pd-catalyzed hydrogenolysis after converting it into allylic formate, yielding the c.ro-methylene compound 584. The conversion of carvone (585) into l,3-disiloxy-4-methylenecyclohexane (586) is an example[382]. 

Enantiomers can have striking differences however m properties that depend on the arrangement of atoms m space Take for example the enantiomeric forms of carvone (R) (—) Carvone is the principal component of spearmint oil Its enantiomer (5) (+) carvone is the principal component of caraway seed oil The two enantiomers do not smell the same each has its own characteristic odor... 

Decision on the view of the possible inclusion of carvone m Annex I to Council Directive 91/... 

Examine actual three-dimensional structures for the twc enantiomers of carvone. One occurs naturally in carawa> while the other is found in spearmint oil, and are responsible for the characteristic odors of these materials. Determine which form, R or S, is responsible for which odor. 

Are the energies and dipole moments for the twc enantiomers of carvone (ibuprofen and limonene) the same or are they different Explain your result. 

Dihydrocarveol, Cj H gO, is a natural constituent of caraway oil, and is also obtained by the reduction of carvone. 

To prepare it artificially, 20 grams of carvone are dissolved in 200 c.c. of absolute alcohol and 24 grams of sodium are added. Towards the end of the reaction water is added, and the product is then distilled with steam. 

The above values apply to natural dihydrocarveol from caraway oil. A specimen prepared by the reduction of carvone had a specific gravity 0-927 at 20° and refractive index 1-48168. i (r.ii4.j... 

Dihydrocarveol is obtained from both optical forms of carvone, and is optically active in the same sense as the ori nal carvone. It has the following constitution —... 

G. Vavon has examined the hydrogenation of carvone, in presenc of platinum black as a catalyst, and shown that it takes place in three entirely distinct phases. Carvone fixes successively three molecules of hydrogen, giving dextro-carvotanacetone, then tetrahydrocarvone, and finally carvomenthol. 

It is an oil having an odour resembling those of carvone and menthone. Its characters are as follows —... 

It results, artificially, from the treatment of carvone by potash or phosphoric acid, and by heating camphor with iodine. 

Carvone, a substance responsible for the odor of spearmint, has the following structure. Tell how many hydrogens are bonded to each carbon, and give the molecular formula of carvone. 

Carvone is the major constituent of spearmint oil. What products would you expect from reaction of carvone with the following reagents ... 

Numerous examples of the different biological effects of enantiomers are available. One of the enantiomers of limonene smells of lemons, the other of oranges one of carvone smells of caraway, the other of spearmint These differences obviously have important... 

The main constituents of spearmint oil are /-carvone (Fig. 13.12.7) and /-limonene (Fig. 13.12.8). Oil of spearmint contains from 45 to 60% l-carvone, 6 to 20% of alcohols, and 4 to 20% of esters and terpenes, mainly /-limonene and cineole (see Fig. 13.12.4)J2J The optically isomeric form of carvone, d-carvone, is found in oil of caraway and oil of dill. Carvone appears to co-occur with limonene when present in a plant. 

Heating of carvone in water at 210 °C for 10 min afforded 8-hydroxy-p-menth-6-en-2-one, the equilibrium position favoring the starting material by a factor of 4 1. The hydroxymenthenone, although in equilibrium with the starting material, also underwent elimination of water and isomerization to carvacrol, giving a 1 1 1 mixture of these three substances at 230 °C after 10 min. At 250 °C, for 10 min, carvone isomerized to carvacrol almost quantitatively (Scheme 2.11) [47]. 

By a traditional method, a- and /i-iononcs can be converted to ionene, catalyzed by HI along with small amounts of phosphorus. A cleaner cydization occurred by heating /i-ionone in water at 250 °C in the MBR [50]. In the workup the usual exhaustive washing procedures were unnecessary. Similarly, as mentioned above, carvacrol was prepared almost quantitatively, by isoaromatization of carvone in water at 250 °C for 10 min [47]. A conventional, literature method utilized acidic conditions, took a longer time and proceeded in lower conversion. The above examples show that elevated temperatures under neutral pH conditions can offer advantages over acidic (or basic) reagents at lower temperatures. 

Other reactions shown to occur at the same rate under the two heating methods include the acid-catalyzed isomerization of carvone 40 to carvacrol 41 [33], and ene reactions involving carbonyl enophiles (Scheme 4.21) [32], The former reaction was performed in a mixture of chlorobenzene (slightly polar) and dioxane (nonpolar) and in the latter reaction a large excess of 1-decene was used and so the reaction was effectively performed in a solution of low polarity. 

The Wilkinson catalyst reduces external double bonds much faster than the internal ones as in the hydrogenation of carvone (equation l)7. 

Literature examples include one-, two-, and three-step hydrogenation reactions, hi each case, the reactant and product concentrations were monitored, as were intermediates or side reaction products as necessary. Simple peak height or area measurements were sufficient to generate reaction profiles for the reduction of cyclohexene [116] and of l-chloro-2-nitrobenzene [117]. However, for more spectrally complex systems, such as the reduction of carvone and of 2-(4-hydroxyphenyl) propionate, multivariate curve resolution (MCR) was required [117]. 

Humans,mole rats" and squirrel monkeys" can distinguish between suprathreshold concentrations of the two enantiomers of carvone. The (47 )(—)-carvone is detected at lower concentrations than the (45) (-l-)-carvone by humans. At equivalent suprathreshold concentrations some individuals perceive (45) (-f)-carvone to be more intense than its... 

Bouwmeester HJ, Davies JAR, Toxopeus H, Enantiomeric composition of carvone, limonene, and carveols in seeds of dill and annual and biennial caraway YiLnexies, JAgricFood Chem 43 3057-3064, 1995. 

Hormann CA, Cowart BJ, Olfactory discrimination of carvone enantiomers, Chem. Senses 18 573, 1993. 

Pike LM, Enns MP, Hornung DE, Quality and intensity differences of carvone enantiomers when tested separately and in mixtures, Chem Senses 13 307—309, 1988. 

Limonene is a liquid with lemon-like odor. It is a reactive compound oxidation often yields more than one product. Dehydrogenation leads to / -cymene. Limonene can be converted into cyclic terpene alcohols by hydrohalogenation, followed by hydrolysis. Nitrosyl chloride adds selectively to the endocyclic double bond this reaction is utilized in the manufacture of (—)-carvone from (+)-limonene (see p. 61). 

The preferred industrial method of carvone synthesis utilizes the selective addition of nitrosyl chloride to the endocyclic double bond of limonene. If a lower aliphatic alcohol is used as solvent, limonene nitrosochloride is obtained in high yield. It is converted into carvone oxime by elimination of hydrogen chloride in the presence of a weak base. Acid hydrolysis in the presence of a hydroxylamine acceptor, such as acetone, yields carvone [88]. 

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