Camphor Chromic acid

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... 

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). 

Chromic acid and chromium Acetic acid, naphthalene, camphor, glycerol, turpentine, alcohol or... 

Chromic acid and chromium trioxide Chlorine Acetic acid, naphthalene, camphor, glycerol, turpentine, alcohol or other flammable liquids Ammonia, acetylene, butadiene, butane or other petroleum gases, hydrogen, sodium carbide, turpentine, benzene or finely divided metals... 

Scheme 34 shows the synthesis of the bc portion (336), which possessed three of the nine asymmetric centers present in cobyric acid. Retrosynthesis determined that (336) could be obtained, via sulfide contraction, from the two intermediates (337) and (338). Ring c was synthesized from (+)-camphor quinone (not shown). Ring b (337) was obtained from 8-methyl-j8-acetylacrylic acid (339), the two adjacent chiral centers being generated in the required relative orientation by a Diels-Alder cycloaddition with butadiene in the presence of tin(IV) chloride. Fractional crystallization served to resolve the diastereomeric a-phenethylamine salts derived from them, eventually affording the compound (340). Oxidation with chromic acid cleaved the double bond in (340) and one of the newly generated... 

A slightly modified procedure - oxidation with 100 per cent excess of chromic acid at 0 °C for a short period - is adopted for strained bicyclic alcohols (e.g. the oxidation of ( —)-borneol to ( —)-camphor, Expt 5.87) and gives excellent yields of the corresponding ketones. Cycle ketones which are susceptible to acid-catalysed epimerisation are moreover obtained by this procedure in a high degree of epimeric purity. 

Dinitropropane. CH3C(N02)2CH3 white crysts with a camphor-like odor mp 53° with subl bp 185.5° d 1.26g/cc subl at RT. V si sol in w and insol in alkalies. Was first prepd in 1876 by the oxidation of propylpseudonitrole, CH3C(N0)(N02)CH3, with chromic acid, or by simply heating it in air at 100° (Ref 2). Nef (Ref 3) prepd it, among other products, by treating Ag dinitroethane with methyl iodide... 

Pinene forms with one molecule of dry hydrogen chloride, an addition-product, which is called artificial camphor (m.p. 125°) on account of the fact that it resembles camphor in appearance and odor. When this compound is heated with alcoholic potash or with a mixture of anhydrous sodium acetate and glacial acetic acid, hydrogen chloride is eliminated and camphene, an isomer of pinene, is formed. Camphene, the structure of which is not known, melts at 50° it is converted into camphor CioHieO (649) when oxidized with chromic acid. d-Camphene is found in ginger Z-camphene, in turpentine and in citronella and other essential oils. 

By way of comparison it may be pointed out that camphene (4) with chromic acid in aqueous acid gives, as the chief product, camphor (135) and not camphenilanic acid (136), apparently due to fast prior hydration of camphene to isoborneol (83, R = H) (85). This reaction has not been observed with longifolene. Low conversions of camphene to the acid (136) can be, however, achieved by carrying out this oxidation in acetic anhydride-carbon tetrachloride (87), and under these conditions camphene epoxide has been demonstrated (88) as the primary oxidation product. 

A. J. Riban, from 1883 professor of physics and chemistry in the ficole des Beaux-Arts, continued Berthelot s work, and showed that chromic acid readily produces camphor from turpentine. Pelouze had obtained camphor by oxidising borneol. 

Steric Effects.—The consequences upon chemical reaction of non-bonded interactions between enantiomeric pairs of molecules have been discussed an antipodal interaction effect was observed in a reductive camphor dimerization and in a camphor reduction. The full paper on the correlation of the rates of chromic acid oxidation of secondary alcohols to ketones with the strain change in going from the alcohol to the carbonyl product has now appeared. It is concluded that the properties of the product are reflected in the transition state for the oxidation. High yields of hindered carbonyls are available from the corresponding alcohols by reaction with DMSO and trifluoroacetic anhydride (TFAA) indeed, the more hindered the alcohol, the higher the yield of carbonyl compound reported Since the DMSO-TFAA reaction occurs instantaneously at low temperatures (<—50°C), it is possible to oxidize alcohols that form stable sulphonium salts only at low temperature. Thus, ( )-isoborneol reacts at room temperature to give camphene, the product of solvolysis of the sulphonium salt the oxidation product, ( + )-camphor, was obtained by the addition of base at low temperature. 

Chromic(VI) acid Acetic acid, acetic anhydride, acetone, alcohols, alkali metals, ammonia, dimethylformamide, camphor, glycerol, hydrogen sulflde, phosphorus, pyridine, selenium, sulfur, turpentine, flammable liquids in general... 

Bomeol is oxidized to camphor with chromic or nitric acid dehydration with dilute acids yields camphene. Bomeol is readily esterified with acids, but on an industrial scale bornyl esters are prepared by other routes. For example, levorotatory bomeol is synthesized industrially from levorotatory pinenes by Wagner Meerwein rearrangement with dilute acid, followed by hydrolysis of the resulting esters [86]. 

Chromic Atfd vrith acetic acid naphthalene, camphor alcohol, glycerine turpentine and other flam-mabte liquids. 

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