— 192 — 



solution. In the latter case the reaction usually takes a normal course. 

 Basing themselves upon the results thus obtained, Bredt and Sandkuhl 1 ), 

 for the purpose of preparing the /?-hydriodo-bornylene carboxylic acid 

 solution, saturated the bornylene carboxylic acid in a solution of glacial 

 acetic acid with hydriodic acid. The free /2-hydriodo-bornylene carboxylic 

 acid occurs in beautiful needle-shaped crystals, m. p. 129 to 130°. Its 

 sodium salt, in analogy with /?-hydrobromo-bornylene carboxylic acid, 

 yields, when boiled with soda-liquor, bornylene carboxylic acid together 

 with small proportions of bornylene (m. p. 113°; b. p. 146° at 745,5 mm.; 

 Hd2oo — 23,68° in toluene solution). When heated with glacial acetic 

 acid + sulphuric acid, bornylene yields a body with an odour reminding of 

 isobomyl acetate, b. p. 103 to 104° (14 mm.) which upon saponification 

 afforded a borneol with a not very sharp m. p. 



Bornylene carboxylic acid yields a dibromo-derivative, m. p. 159 to 160°. 

 When /?-hydriodo-bornylene carboxylic acid is reduced it yields hydro- 

 bornylene carboxylic acid (b. p. 171° at 22 mm.). The chloride boils bet- 

 ween 114 and 115° (14 mm.), and the amide has m. p. 166 to 167°. 



Cinnamic Acid. Several detailed investigations into the conditions 

 of isomerism in cinnamic acid have again been published, and to these 

 we will briefly refer in connection with our previous notes 2 ). E. Erlenmeyer 3 ) 

 in his paper on labile interconvertible isomerides of similar structure, dis- 

 cusses the conditions of isomerism which have been observed in the various 

 cinnamic acids. Investigation of the labile cinnamic acids of the iso-series 

 showed that here we have to deal with cases of isomerism which cannot 

 be explained either by the atomic structure or stereo-chemically, and of 

 which the differences must be assigned to a still unknown difference in 

 the position of some parts or other of the molecules. Although the labi- 

 lity of the acids is not so great as to cause the differences in the modi- 

 fications to disappear in the melting, it would yet seem that certain con- 

 ditions exist in which the lability is very considerable, and this explains 

 why Stobbe 4 ) (see p. 195) in one case obtained from the three acids solutions 

 in which by his experimental method he was unable to detect any dif- 

 ferences. The conditions referred to above, however, cannot as yet be 

 experimentally determined. In forming a judgment of the conditions of 

 isomerism which exist in this case the fact is of great importance that the 

 tfZfo-acid, by being brought under the influence of heat, is finally converted 

 into the most labile of all acids, — the iso-acid of Erlenmeyer sen. Th| 



*) Journ. f. prakt. Chem. II. 84 (1911), 778. 



2 ) Comp. Report April 1907, 155; April 1909, 138; October 1909, 210: April 1910, 188; 

 October 1910, 203. 



3 ) Biochem. Zeitschr. 34(1911), 306. Copies of this and the other reprints here referred 

 to were kindly sent to us by the authors. 



4 ) Berl. Berichte 43 (1911), 506. 



