COOC 2 H E 



C 6 H 4 



x OC 3 H 5 

 i. 



O-allyl ethylsalicylate. 



Notes on scientific research. 



/COOC2H* 

 C 6 H 3 — OH 



^CH 2 CH:CH 2 

 II. 



C-a!lyI ethylsalicylate. 



145 



yCOOU 

 CeHo-OH 



CH:CHCH ;; 



in. 



Propenyl salicylic acid. 



Acids and lactones. 



Dehydrocamphoric acid. In a voluminous paper, J. Bredt 1 ) communicates the 

 result of his research into dehydrocamphoric acid and its derivatives. He has discovered 

 interesting manifestations of isomerism in this acid and its derivatives, and these he 

 explains with the aid of perspective illustrations. Bredt gives detailed directions 

 for the preparation of dehydrocamphoric acid and its derivatives, for the particulars 

 of which we must refer to the original paper. We can only mention here that from 

 the phenylester of chlorocamphoric acid with quinoline a satisfactory yield of phenyl 

 dehydrocamphorate is obtained as a result of the elimination of hydrochloric acid. 

 Free ^-dehydrocamphoric acid has m. p. 202 to 203°; [«] D2 io + 118,6° (12,98 p. c. solution 

 in chloroform) and +113,8° (7,83 p. c. solution in absolute alcohol), (d + I)- Dehydro- 

 camphoric acid melts at 228° (from acetic ether). 



CH:CC0 2 H 



I 



C(CH 3 ) 2 

 I 

 CH 2 C(CH 3 )-C0 2 H 



Dehydrocamphoric acid. 



When dehydrocamphoric acid is oxidised with nitric acid or potassium permanganate 

 it gives rise to camphoronic acid, and with potassium permanganate it is probable that 

 a keto-acid is formed as an intermediary product. A dibasic acid, probably a dihydroxy- 

 camphoric acid, also results from the permanganate-oxidation. When dehydrocamphoric 

 acid is distilled under ordinary pressure it is in part converted into the anhydride of 

 isodehydrocamphoric acid and in part decomposed into camphonenic acid 2 ) and into a 

 liquid acid of the same constitution, which latter, however, has not yet been obtained 

 in the absolutely pure state. Isodehydrocamphoricanhydride (m. p. 185,5°), when boiled 

 with water, is converted into wodehydrocamphoric acid (m. p. 181 to 182°). The reaction 

 of hydrobromic acid with ^-dehydrocamphoric acid gives rise to two stereo-isomeric 

 hydrobromides of dehydrocamphoric acid, namely, d-bromo-3-t'socamphoric acid (m. p. 232°) 

 and d-bromo-3-m-camphoric acid (m. p. 158 to 160°). When reduced with zinc-dust 

 in acid solution, the bromocamphoric acid with m. p. 232° afforded iso-camphoric acid 

 (cis-trans-camphoric acid, m. p. 173°) and the bromocamphoric acid with m. p. 158 to 160°, 

 gave m-camphoric acid admixed with a little cis-trans- acid. The action of hydrobromic 

 acid upon (d -+- ^-dehydrocamphoric acid led to (d-f 0-bromo-3-isocamphoric acid (m. p. 

 239 to 240°), which, when reduced with zinc dust, was converted into (d -j- 1)-cis-tnvis- 

 camphoric acid. Komppa's designation "/?-bromocamphoric acid" is not singular in its 

 meaning, because there must be two ^-bromocamphoric acids in isomeric position. 

 The compound might with equal appropriateness be called ;.'-bromocamphoric acid, and 

 for this reason Bredt proposes the designation bromo-3-camphoric acid. Bromo-3-ci$- 



x ) Liebigs Annalen 395 (1913), 26. 



2 ) For the nomenclature see below. 



10 



