ON THE CONSTITUTION OF CAMPHOR. 



315 



u-Dihydroxydihydrocampholenic acid is dextrogyrate and on oxidation 

 with chromic acid yields inactive isoketocamphoric acid, and with nitric 

 acid gives isodiketocamphoric acid. Both of these latter contain acetyl 

 groups, and isoketocamphoric acid is converted into bromoform and iso- 

 camphoronic acid (E. 1. a. ii.) on treatment with cold hypobromite. These 

 changes are expressed by Tiemann ^ as follows : — 



CMe,— OH— CE, 



CH, 

 CMe =CH COOH 



n-Camplioleuic Acid. 



OMe,— OH— CH,. 



1 

 OH, 



-CH C 



CJIe„ — CH — CH, 



OH,. 



CMe„ — CH CHj 



CH.. 



CMe — CH COOH 



I I 



OH OH 



o-Uihydroxydihyilro- Isoketocamphoric 



campholenic Acid. Acid. 



4- ^4 



CMe^ — CH — CH^ CMe,, — CH — CH. 



COMe COOH COOH COOH COOH COOH 



Isocamplioronic 

 Acid. 



CMe, — CH - 



-OH, 



CH, 



CHMe— CO COOH 

 Pinouic Acid. 



CO 



C!OMe COOH COOH 



Isodiketocamplioric 



Acid. 



COOH COOH COOH 

 Diinethyltricarballylic 

 Acid. 



This scheme expresses the foregoing facts in a highly satisfactory 

 manner, including the cessation of inactivity with the passage from 

 fi-dihydroxydihydrocampholenic acid to isoketocamphoric acid, and 

 appears, moreover, to be the only mode of doing so. The inadequacy of 

 any formula for campholenic acid or pinonic acid which does not 

 contain the group 



. CMe . CMea 

 C C 

 is shown by the fact that one of the products obtained by oxidising pinonic 

 acid is hydroxytrimethylsuccinic acid, COOH . CMe(OH) . CMe., . COOH. 

 /3-Dihydroxydihydrocampholenic acid (of course inactive, since /3-cam- 

 pholenic acid has this property) on further oxidation with dilute per- 

 manganate yields oxalic and y-acetyldimethylbutyric acid, which affords 

 a-dimethylglutaric acid on treatment with alkaline hypobromite. Tiemann 

 expresses these facts in the following way : — 



CMe. — CH-- 



CJie. — CH— CH. 



! ' Jh i ' 



CHMe CH COOH 

 /3-Camplioleuic Acid. 



-CH,. 



CH . OH I 



I I 



CHMe — CH . OH COOH 

 ^-Diliydroxydihydro- 

 campliolcnic Acid. 



CMC— CH,.— CH.. 



+ COOH. COOH 



COMe COOH 



y-Acetyldimethyl- ^q^^^^^ ^^id. 

 butyric Acid. 



Such 



change 



as that assumed in the transformation of the di- 

 hydroxy-acid is obviously inadequate without furtlier proof. Moreover 

 the inactivity of /j-campholenic acid receives no explanation whatever, as 

 it is scarcely conceivable that the asymmetry of the carbon atom to which 

 the activity of « -campholenic acid is clue has been in any way destroyed. 

 Proceeding backwards in a logical manner from the fact of the 

 formation of y-acetyldimethylbutyric acid and oxalic acid, we are led 

 almost inevitably to the formula for /3-campholenic acid which was first 

 suggested by Bouveault,'- namely — 



CMe=C 



-CH, 



CH, 



I 

 CMe.,— CH, COOH 



Her., 29, 3000, iind 30, 40!». 



■' Bull. Soc. Chem. [iii.], 19, S65. 



