A-Camphene

It is possible, however, that camphene hydrochloride is not a uniform body, but that some of the terpene suffers some rearrangement in the molecule by the action of hydrochloric acid, and that the hydrochloride consists of a mixture of a-camphene hydrochloride and /8-camphene hydrochloride there is, however, no evidence to suggest that camphene itwlf is a mixture of two terpenes, so that the two camphenes are not known to exist. Aschan obtained an alcohol, camphene hydrate, by acting on camphene hydrochloride with milk of lime, a reagent which does not produce molecular rearrangement in the terpene nucleus. 

The LIS (Lanthanide Induced Shift) NMR technique is useful for such analysis25 and the separation of olefin enantiomers such as limonene, a-camphene and /J-pinene has been performed upon addition of silver salts such as Ag(fod) or Ag(hfc) to the commonly used lanthanide chiral salts such as Ln(tfc )3 or Ln(hfc)3, where fod = 6,6,7,7,8,8,8-heptafluoro-2,2-dimethyloctanedione, hfc = heptafluoro-3-butyrylcam-phorato and tfc = trifluoroacetylcamphorato. 

Figure 3 - Initial activity as a function of Nai and Al-Na. ,0 - a-pinene A, A - camphene.

Plagiochila acanthophylla ssp. japonic a Camphene a-Pinene P-Pinene... 

Borneol and isoboineol are respectively the endo and exo forms of the alcohol. Borneol can be prepared by reduction of camphor inactive borneol is also obtained by the acid hydration of pinene or camphene. Borneol has a smell like camphor. The m.p. of the optically active forms is 208-5 C but the racemic form has m.p. 210-5 C. Oxidized to camphor, dehydrated to camphene. 

Ordinary commercial camphor is (-i-)-cam phor, from the wood of the camphor tree. Cinnamonum camphora. Camphor is of great technical importance, being used in the manufacture of celluloid and explosives, and for medical purposes, /t is manufactured from pinene through bornyl chloride to camphene, which is either directly oxidized to camphor or is hydrated to isoborneol, which is then oxidized to camphor. A large number of camphor derivatives have been prepared, including halogen, nitro and hydroxy derivatives and sulphonic acids. 

By oxidation with permanganate it forms pinonic acid, C,oH,<503, a monobasic acid derived from cyclobutane. With strong sulphuric acid it forms a mixture of limonene, dipentene, terpinolene, terpinene, camphene and p-cymene. Hydrogen chloride reacts with turpentine oil to give CioHijCl, bomyl chloride, artificial camphor . 

This involves the formation of a carbenium ion which is best described as a hybrid of the two structures shown. This then rearranges by migration of a bond, and in so doing forms a more stable tertiary carbenium ion. Elimination of a proton yields camphene. 

Chlorinated Terpenes. A group of incompletely characterized insecticidal compounds has been produced by the chlorination of the naturally occurring terpenes. Toxaphene [8001-35-2] is prepared by the chlorination of the bicycHc terpene, camphene [79-92-5] to contain 67—69% chlorine and has the empirical formula C QH QClg. The technical product is a yellowish, semicrystalline gum (mp 65—90°C, d 1.64) and is a mixture of 175 polychloro... 

Uses ndReactions. a-Pinene (8) is useful for synthesizing a wide variety of terpenoids. Hydration to pine oil, acid-catalyzed isomerization to camphene, thermal isomerization to ocimene and aHoocimene, and polymerization to terpene resins are some of its direct uses. Manufacture of linalool, nerol, and geraniol has become an economically important use of a-pinene. 

Acid-cataly2ed isomerization of a-pinene is carried out by heating with catalysts or other activated clays. Camphene (13) and tricydene... 

Camphene Manufacture. Camphene (13) is produced by the reaction of a-pinene (8) with a Ti02 catalyst (80). Preparation of the catalyst has a great influence on the product composition and yield. Tricydene (14) is formed as a coproduct but it undergoes the same reactions as camphene thus the product is generally used as a mixture. They -menthadienes and dimers produced as by-products are easily removed by fractional distillation and the camphene has a melting poiat range of 36—52°C, depending on its purity. Camphene is shipped ia tank cars, deck tanks, and dmms. 

Uses ndReactions. Camphene is used for preparing a number of fragrance compounds. Condensation with acids such as acetic, propionic, isobutyric, and isovaleric produce usehil isobomyl esters. Isobomyl acetate (41) has the greatest usage as a piae fragrance (81). The isobomyl esters of acryhc and methacrylic acids are also usehil ia preparing acryUc polymers. 

The Prins reaction with formaldehyde, acetic acid, acetic anhydride, and camphene gives the useful alcohol, 8-acetoxymethyl camphene, which has a patchouli-like odor (83). Oxidation of the alcohol to the corresponding aldehyde also gives a useful iatermediate compound, which is used to synthesize the sandalwood compound dihydo- P-santalol. 

When camphene reacts with guaiacol (2-methoxyphenol), a mixture of terpenyl phenols is formed. Hydrogenation of the mixture results ia hydrogenolysis of the methoxy group and gives a complex mixture of terpenyl cyclohexanols (eg, 3-(2-isocamphyl) cyclohexanol [70955-71 (45)), which... 

Most synthetic camphor (43) is produced from camphene (13) made from a-piuene. The conversion to isobomyl acetate followed by saponification produces isobomeol (42) ia good yield. Although chemical oxidations of isobomeol with sulfuric/nitric acid mixtures, chromic acid, and others have been developed, catalytic dehydrogenation methods are more suitable on an iadustrial scale. A copper chromite catalyst is usually used to dehydrogenate isobomeol to camphor (171). Dehydrogenation has also been performed over catalysts such as ziac, iadium, gallium, and thallium (172). 

OC-Santalol. Sandalwood oil is comprised of mainly (90%) a- and P-santalol, which gives the oil the woody, tenacious sandalwood odor. An impure a-santalol [115-71 -9] (100) can be isolated by the distillation of the oil. P-Santalol [77-42-9] (101) is also isolated but ia much smaller amounts. The price of sandalwood oil, E. Indian, ia 1995 was 286/kg, and the oil from Indonesia was 187/kg (69). The high price of these oils has created the need to synthesize new materials with the sandalwood odor. The terpenophenols are manufactured by condensation of camphene with phenoHc compounds followed by hydrogenation to the cycloaUphatic alcohols (194). 

Camphene [565-00-4] M 136.2, m 51-52°, b 40-70 /10mm. Crystd twice from EtOH, then repeatedly melted and frozen at 30mm pressure. [Williams and Smyth J Am Chem 5oc 84 1808 1962.] Alternatively it is dissolved in Et20, dried over CaCl2 and Na, evaporated and the residue sublimed in a vacuum [NMR Chem Ber 111 2527 1978]. 

Fig. 6.8. Most metals solidify with a dendritic structure. It is hard to see dendrites growing in metals but they con be seen very easily in transparent organic compounds like camphene which - because they have spherical molecules - solidify just like metals.

Both acetolyses were considered to proceed by way of a rate-determining formation of a carbocation. The rate of ionization of the ewdo-brosylate was considered normal, because its reactivity was comparable to that of cyclohexyl brosylate. Elaborating on a suggestion made earlier concerning rearrangement of camphene Itydrochloride, Winstein proposed that ionization of the ero-brosylate was assisted by the C(l)—C(6) bonding electrons and led directly to the formation of a nonclassical ion as an intermediate. 

Carbocation rearrangements occur in the reactions of some secondary alco hols with DAST, thus isobutyl alcohol gives a mixture of isobutyl fluoride and tert-hxAy] fluonde [95] (Table 6), and both bomeol and isoborneol rearrange to the same 3-fluoro-2 2,3-tnraethylbicyclo[2 2 IJheptane (72-74%) accompanied by camphene [95]... 

Figure 10.11 Comparison of the mass spectra of a neroli oil peak (camphene) obtained by HPLC-HRGC-MS (a) and GC-MS (b) with a library specti um of the same compound (c). Reprinted from Perfumer and Flavorist, 21, L. Mondello et al., On-line HPLC- HRGC in the analytical chemistiy of citms essential oils , pp. 25-49, 1996, with permission from Allured Publishing Coip.

A 1-liter three-necked flask equipped with a mechanical stirrer and two dropping funnels is charged with a solution of 42 g (0.176 mole) of sodium periodate in 145 ml of acetone and 180 ml of water. To the stirred solution, camphene (6.7 g, 0.049 mole) is added in small portions. The reaction vessel is then flushed with nitrogen and is main-... 

Tardy ha.s examined an Algerian oil of specific gravity 0 991 and optical rotation +62°. He found present pinene, pliellandrcne, isnehone, mcthyl-chavicol, auethol, a sesquiterpene, and a little thymo-hydroquinotie. Scliimmcl A Co. find camphene in fennel oil, but are not able to confirm the presence of cymene. Traces ol basic com-ponnds were also detocted. 

Camphene is the only well-recognised terpene which occurs in nature in the solid condition. It occurs, like pinene, in both optically active forms. The constitution of this terpene has been a matter of considerable difference of opinion, and the constitution assigned to it by Semmler based on its similarity to bomylene was thought by many to be finally accepted. Recent researches, however, have clearly established that the formula assigned to it by Wagner is the correct one. 

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