1-Borneol

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. 

Present in citronella and valerian oils, tur penline, ginger, rosemary and spike oils. It is produced artificially by the elimination of hydrogen chloride from bornyl chloride (artifi cial camphor) or from isobornyl chloride, by the dehydrogenation of borneol and isobor-neol and by the action of elhanoic anhydride on bornylamine. Chiral. 

The structure of the bicychc monoterpene borneol is shown in Figure 26 7 Isoborneol a stereoisomer of borneol can be prepared in the labora tory by a two step sequence In the first step borneol is oxidized to camphor by treatment with chromic acid In the second step camphor is reduced with sodium borohydride to a mixture of 85% isoborneol and 15% borneol On the basis of these transformations deduce structural formulas for isoborneol and camphor... 

The glucosides of menthol, citronellol, nerol, geraniol, cw-myrtenol, L-borneol, linalool and a-terpineol yielded yellow-green fluorescent chromatogram zones in long-wavelength UV light (2 = 365 nm). The same applied to arbutin (hRf 45 — 50). 

Reduction of l-methyl-2-alkyl-.d -pyrroline and l-methyl-2-alkyl-.d -piperideine perchlorates with complex hydrides prepared in situ by partial decomposition of lithium aluminum hydride with the optically active alcohols (—)-menthol and (—)-borneol affords partially optically active l-methyl-2-alkyl pyrrolidines (153, n = 1) and 1-methy 1-2-alkyl piperideines (153, n = 2), respectively (241,242). 

Thin-Layer Chromatography TLC) The function of TLC in organic synthesis is primarily one of allowing the experimenter to follow the progress of the reaction without actually interrupting the reaction. Since successful TLC can be carried out on a minute scale, only a very small fraction of the reaction mixture need be withdrawn and subjected to analysis. The following example of the TLC analysis of the chromic acid oxidation of borneol, described by Davis (3), is a useful model. 

One milliliter each of the borneol solution and the oxidizing solution are mixed in a test tube and briefly shaken. A TLC slide is spotted with the borneol solution, the camphor solution, and the ether layer of the reaction mixture. Spotting is done by means of a capillary melting point tube used as a dropper and filled with a 5 mm sample. The slide is developed in a wide-mouth jar containing a filter paper liner and a few milliliters of chloroform (Fig. A3.20). After development (the solvent front rises to within 1 cm of the top), the slide is removed, the solvent is allowed to evaporate, and the slide is placed in a covered wide-mouth jar containing a few crystals of iodine. The spots readily become visible and the progress of the reaction can easily be followed. With periodic shaking, the oxidation is complete in about 30 minutes. 

The acc-tie c.-tur of eraniol is more yi odounned ui the leaf oils than is that of borneol. and it couiiciai .- to meriiasii io the several tuember.a leseclion, until a maximum of OTri 00 rr ( / ni. is reached tn ibe... 

This oil contains about -IQ per cent, of terpenes, priuoipally terpinooe, terpineol, terpineuol-J, and small ijuantitics ol caters. Possibly borneol aod camphor nre present io tcacea. 

The oil was found to conlain about 6 per cent, of piuene, 60 per cent-Of euoalyptol, 9 per cent, of borneol, 19 per ceul. of linalyl acetate, with a little camphor, meth. i salicylate, and sesqnitci-pene alcohol. 

The sharp (camphoraceous ) alcohols of the terpene alcohols of the borneol type. 

It is best prepared, however, by converting the alcohol, borneol, into bomyl chloride. The bornyl chloride is carefully dried and then gently warmed with an equal weight of aniline. The mixture is then heated to the boiling-point of aniline when the reaction, which is suddenly violent, 18 quickly completed. The reaction mass is neutralised by hydrochloric acid and distilled over in a current of steam. Gamphene is rapidly condensed and solidifies to a crystalline mass. 

Borneol forms crystalline compounds with chloral and bromal, the. former melting at 55° and the latter at 104° to 105°. 

Pickard and Littlebury have carried out a series of investigations on the separation of the optically active borneols and isobomeols, which is of particular interest, as the method of separation can probably be applied to various other similar bodies. This method depends on the... 

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