ON THE CONSTITI'TION OF CAMPHOR. 319 



represents a substituted adipic acid, derivatives of which are almost 

 invariably incapable of affording anhydrides when treated by the ordinary 

 processes. Using the Perkin-Bouveault formula, homocamphoric acid 

 would have the structure 



/CH2.CH.CH0.COOH 



r / 



CMe, / 



\7 



• CMe.COOH 



which is that of a glutaric acid, and should therefore be expected to yield 

 an anhydride fairly readily, unless the structure is that of a trans-acid, an 

 assumption which appears to be excluded by the fact that d-camphorie 

 acid from which it is easily obtained is a cis-acid, the corresponding 

 ti'ans-aciA being represented by iso camphoric acid. 



(c) T/ie Formation of Camphor in larf/c Amount by distillimj the Barium Salt of 

 ' Homocamphoric Acid (compare B. 2. c). 



As pointed out by Bredt and Kosenburg,' Wislicenus - and Perkin 

 and Crossley,-' the formation of considerable quantities of ketones by 

 distillation of the barium or calcium salts of dibasic acids, in the simple 

 manner here observed, is met with only amongst the derivatives of adipic, 

 pimetic, and suberic acids, and never amongst those of glutaric acid, so 

 that here again the Perkin-Bouveault formula appears inadmissible. 



(d) The extraordinarij Readiness with which p-Ci/mene and its Derivatives are 



ohtained from Camphor. 



This change, a knowledge of which assisted Bredt in devising his 

 formula, is very readily understood by means of it : 



/CH C.CHMea 



' \ /\ 



CH2 CH. CH CH 



I CMe. I " -> II 



CH2 CO CH CH 



^ CMe CMe 



Camphor. ;7-Cymene. 



(e) The readu Formation of the Lactonic Acid, Camphanic Acid from Bromocam- 

 phoric Acid or its Anhydride, and of it^ Ethyl Fster by heatiny Biethjl 

 Bromocamphorate. 



When ^.t'-bromocamphoric acid or its anhydride (obtained by the direct 

 bromination of camphoric acid) is treated with water, alkalis, or sodium 

 acetate dissolved in glacial acetic acid, it yields camphanic acid, a very 

 stable lactonic acid. The ijreat stability of the lactone ring of camphanic 

 acid excludes the idea that it is of the nature of a /3-lactone, so that it 

 must be a y-lactone. ?f;-Bromocamphoric acid would therefore appear to 

 be a y-bromo-acid, and, in accordance with Yolhardt's rule, it should also 



' Annalen, 28?, 1.3. 

 2 Ibid., 275,309. • Trans. Chem. Soc, IB, 6. 



