Camphenic acid

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 . 

CAMET catalyst 14C-Amino acids Camolar [609-78-9] Camoquin [6398-98-7] Camouflage Campesterol [474-62-4] Camphene [79-92-5]... 

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... 

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. 

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). 

Of synthetic importance is the Wagner-Meerwein rearrangement especially in the chemistry of terpenes and related compounds." For example isoborneol 5 can be dehydrated and rearranged under acidic conditions to yield camphene 6 ... 

Camphene is prepared artificially by the isomerisation of pinene with sulphuric acid or by the withdrawal of HCl from pinene monohydrochloride, or by the action of heat in the presence of acetic anhydride on bornylamine, CjjHj7NH2, which causes the withdrawal of ammonia and leaves camphene, as follows —... 

The identification of camphene is best carried out by its conversion into isobomeol under the influence of acetic acid in the presence of sulphuric acid. In order to effect this conversion, 100 grams of the fraction containing the terpene in substantial quantity are mixed with 250 grains of glacial acetic acid and 10 grams of 50 per cent, sulphuric acid. Tne mixture is heated for two to three hours on a water-bath to a temperature of 50° to 60°. At first the liquid separates into two layers, bat soon becomes homogeneous and takes on a pale red colour. Excess of water is added, and the oil which is precipitated, and which contains the isobomeol in the form of its acetate, is well washed with water repeatedly. It is then saponified by heating with alcoholic potash solution on a water-bath. The liquid is then evaporated and extracted with water, and the residue recrystallised from petroleum ether. 

Camphene hydrochloride, Cj(,H gHCl, is prepared by passing dry hydrochloric acid into an alcoholic solution of camphene. When re-ctystallised from an alcoholic solution containing excess of hydrochloric acid, it melts at 155° (or possibly a few degrees lower).- Melting-points from 149° to 165° have been recorded for this compound, but the products examined were probably not in a state of purity. 

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. 

Camphene forms a well-defined nitrite, and a nitroso-nitrite, when treated in the following manner A well-cooled solution of camphene in petroleum ether is mixed with a saturated solution of sodium nitrite, and dilute acetic acid is added. The mixture is well stirred, being kept cool all the time. Camphene nitrosonitrite, CuHi NjOj, separates and on recrystallisation forms crystals which decompose at about 149°. The petroleum ether solution, which has been filtered off from this compound, is shaken with a concentrated solution of pK)tassium hydroxide, which removes camphene nitrosite, CjQHigNjOj, in the form of its potassium salt. When this is decomposed with acids it yields the free nitrosite. This compound is a greenish oil, with a pleasant odour, easily decomposing when heated to 50°. 

Pinene hydrochloride is treated by one of the reagents which abstract-HCl, and so converted into camphene q.v.). This is heated with acetic and sulphuric acids, and so converted into isobornyl acetate. Canmhor results in the usual manner. 

After addition of a few milliliters at 15°C, the thick slurry thins slowly and the remainder of the sulfuric-glacial acetic acid mixture was added at 0° to 2°C. A total of about 2 hours was required for the addition. After addition, stirring was continued for 15 minutes. Then dropwise, over an hour, a solution of 178 g (1.3 mols) of dl-camphene in 50 ml of glacial acetic acid was added while keeping the temperature at about 0°C ( 3°C). 

Isoborneol (Problem 27.37) is converted into camphene on treatment with dilute sulfuric acid. Propose a mechanism for the reaction, which involves a carbocation rearrangement. 

Melilotic acid 3. Dihydroxy-stearic acid 3. Camphene 3. Phloretin... 

The dehydration of d-2-endo- and i-2-ca o-bornanols was studied by Watanabe et al. (73) at 275° using an acidic alumina and the same alumina modified by the introduction of piperidine to the hydrocarbon solution of the bornanols. Under nonacidic conditions of dehydration, 2-exo-bornanol formed 4.3% tricyclene, 95.2% camphene, and 0.5% camphor. 2-ewdo-Bornanol under similar conditions formed 12.5% tricyclene and 86.5% camphene. 

The function of piperidine was to neutralize the relatively strong acidic sites of the alumina and still leave the weak acidic sites to act catalytically. In the presence of acidic alumina a reversible isomerization of camphene to tricyclene occurs. 

The retention of optical activity of camphene rules out methyl migration (Nametkin rearrangement) (71) or a symmetrical intermediate. On the acidic alumina at low contact time the retention of optical activity is high, about 80%. At longer contact time, however, there is essentially complete racemization. Hence, the dehydration mechanism seems to be the same on the acidic and on the base-modified alumina. The acidic alumina, however, causes the readsorption of the dehydration product leading to isomerization and equilibration. 

Butyne, see 1,1,1-Trichloroethane Butyric acid, see Butane Camphenilone, see Camphene Carbamic acid, see Asulam. Carbofuran... 

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