_ NOTES ON SCIENTIFIC RESEARCH. 127 
= Carvotanacetone (4®-menthenone-2) used for preparing its dibromide (/,6-dibromo- 
‘menthanone-2) may be obtained after various methods, in the simpliest way by 
abstracting hydrogen bromide from monobromocarvomenthone. The dibromide, on 
shaking with aqueous potash, dissolves nearly entirely, the principal product of the 
reaction being an acid C,)H,sO3, 9-acetyl-8-isopropyl valeric acid. 
* _—_ 1,2-Dibromomenthanone-3 is obtained by brominating 4'-menthenone-3 from 
peppermint oil. On shaking with aqueous potash it yields a solid monobromo- 
_menthanone-3, m. p. 42 to 43°, thymol being formed as by-product. On heating the 
_monobromide- alone or with sodium methoxide thymol is obtained. It is noteworthy 
~ that the monobromide adds bromine only with great difficulty; it is, therefore, not 
_ improbable that the body contains a diagonal bond in lieu of a ethylene bond. At 
any rate, the constitution of the monobromide is not yet ascertained. 
4 4,5-Dibromomenthanone-3, prepared by brominating A*-menthanone-3, yields on 
shaking with aqueous potash a ketonic acid with 10 carbon atoms. 
___ The experimental details on the transformation of hexacyclic ketones into cyclo- 
_ pentanones are to be found in Wallach’s*) 124th paper “On Terpenes and Essential 
" Oils”. In supplementing our abstract”) from the short notice on the same subject 
published in the Nachrichten der K. Gesellschaft der Wissenschaften, Gottingen, we add 
the following. In the nine transpositions of cyclohexanones in to cyclopentanones 
_ described by Wallach via the dibromides of the former, pentacyclic hydroxycarbonylic 
acids are formed as intermediate products. Nothing is yet established as to the 
e further course of the reaction. At any rate Wallach revokes his former assumption 
that merely orthoketones are formed which then undergo the benzilic-acid-transposition. 
3 On the contrary it may be taken for granted that a rather complicated reaction takes 
"place where the hydroxy ketones primarily assumed or reformed from their isomerides 
Suffer at first a ring-rupture and form acids which by intramolecular condensation 
pass over into pentacyclic «hydroxy acids. Such intermediate acids could in some 
cases be proved to be present, but could not yet purified sufficiently for analysis. 
_ As to the further reaction of the dibromides, an excess of 4 per cent. aqueous caustic 
& ‘potash solution was employed. In case of liquid bromides, or of such reacting easily, 
- shaking with the potash solution was sufficient; the higher melting bromides, however, 
_ could be brought to react only with simultaneous heating: For such cases, Wallach employed 
Ss a Beprer vessel, the construction of which is illustrated in the original paper by a drawing. 
The intermediate hydroxy acid resulting in the treatment of cyclohexanone vid 
its dibromide into cyclopentanone, m. p. 103 to 104°, proved to be «-hydroxy cyclo- 
_ pentanone carboxylic acid. 
The dibromide occurring on bromination of 1,.2-methyl- cyclohexanone, m. p. 42 to 
43°, was identical with dibromo-/,3-methyl-1-cyclohexanone-2. 
% ' The acid formed as intermediate product on transforming 17, 4-methyl- -cyclohexanone 
e 1, 3-methyl-cyclopentanone is, in Wallach’s present opinion, methyl-/-e-hydroxy- 
meses 
copentane-3-carboxylic acid; probably, it is formed in various stereoisomeric forms, 
ich would account for the unsharp melting point. 
The acid occurring on formation of 1,3-dimethyl-cyclopentanon-4 from 1,3-dimethyl- 
ini m.p.92 to 93°, is a dimethyl-1, 5-«-hydroxycyclopentanone-4-carboxylic acid. 
___ On transforming trimethyl-1, 3, 3-cyclohexanone-5 into trimethyl-1, 3, 3-cyclopentanone-é, 
2. acid C,H,,O;, m. p. 88 to 89°, occurs, which according to Wallach’s present state- 
n ent, is a trimethyl-1, 3, 3-«-hydroxycyclopentanone-5-carboxylic acid. 
1) Liebig’s Annolen 414 (1918), 296. — ,*) Report 1916, 127. 
