= NOTES. ON SCIENTIFIC RESEARCH. 135. 
In addition, there was to be expected that owing to the well-known great sensitiveness 
of hydrocarbons with semicyclic double bonds a transposition of the isopropylidene- 
cyclopentane (II) into its isomeride, 4*-isopropylcyclopentene (IV), would take place under 
the influence of zinc Chloride. Both the hydrocarbons (Ill) and (IV) are known, and it 
_ could be demonstrated without difficulty that the hydrocarbon from 1.1-methyl-«-hydroxy- 
ethyleyclopentane was nearly pure 1.2-dimethyl-4 t-cyclohexene (Ill). It boils at 135 to 137° 
and smells feebly of terpenes. The nitrosochloride congeals only with difficulty and 
q yields the nitrolpiperidide likewise difficultly; m.p. 120 to 121°. The hydrocarbon, was ' 
identified by its dibromide (m.p. 140°) and by its physical properties. 4A'-/sopropyl- 
cyclopentene was not present in the cyclohexene, in which case its presence would easily 
have been established by means of its difficultly soluble, stable nitrosochloride. Neither 
_ were any products obtained on ozonisation of the hydrocarbon, which would have 
pointed to the presence of eNO fa etal The neutral ozonisation product was 
pure 2.7-diketooctane: — : : : 
‘ye CH, GH. * Clas ; COCH, 
CH, 2. 7-Diketooctane. 
_1.2-Dimethyl-41-cyclohexene. 
This dehydration from 1. -methyl-a-hydroxyethylcyclopentane, with formation of - 
_1.2-dimethyl-41-cycJohexene, is perhaps one of the smoothest reactions leading from 
_ the cyclopentane to the cyclohexane series: — 
ee | CH, 
H.C CH ave 
pre. / CH(OH) CH: H.C A CCH 
| Sed ee ae 
: agave ae *\ ct H.C oe 
; H.C CH, : a CH, ‘ 
4 1. 1-Methyl-a-hydroxyethylcyclopentane. : ‘ Belo qh ie henene 
: In eacin’s Opinion, this easy transformation of a five-ring into a six-ring, also 
taking into consideration the ready passages of hexacyclic to pentacyclic systems, is 
a proof for the fact that in both systems there is no marked difference in the ring-tension. 
Strange to say, the abstraction of water from the homologues of 1.1-methyl-c-hydroxy- 
_ ethylcycopentane does not pass off in one single direction. With 3-zsopropyl-1.1-methyl- 
_«hydroxyethylcyclopentane, this phenomenon had been observed by Meerwein some time 
ago; in addition to 1.2-dimethy]-4-isopropyl-4*-cyclohexene, small quantities of 1.3-di- 
isopropylcyclopentene were formed. He now succeeded in proving that from 1.2.2.3-. 
tetramethyl-1.¢-hydroxyethylcyclopentane there were formed simultaneously, partly by 
extension of the ring system, partly with migration of a methyl group, 1.2.3.3.4-penta- 
methyl-4’-cyclohexene as well as 1.2.2-trimethyl-3-isopropyl-A?-cyclopentene : — 
-H,C-CH C(CH,) 3 We oe Hc CH | C(CHY 
‘Fig 2 3° ~Tig)2. 
Me HC AOC: CH sida a 
CH(OH) CH, 3 . 
= eS awe Wepre | cathe ™>C-CH(CH) 
Me CH, : Ma AC ACCH 
; 2 ; “ . 
oye Gea Ae all Sil 1.2.3.3.4-Pentamethyl- _ DEUTER et ‘i 
A? -cyclohexene. 
/ 
