ON DYNAMIC 1SOMERISM. 201 
dynamic isomerism but also because it proves that the interchange of H 
and OH depends on the separation of a molecule of water. Changes of this 
type frequently occur when alcohols are dissolved in sulphuric acid, as, 
for instance, in the production of tertiary butyl derivatives from isobutyl 
alcohol 
HO.CH,.CHMe,2CH, : CMe, + H,O2CH;.CMe,.0H. 
In the conversion of pinacone into pinacoline the reversible separation of 
a molecule of water would account for the interchange of CH; and OH. 
CMe,,OH Nr _,CHs.CMe, 
| H,0 + ; ZH,O + CMe,.CO.CH,. 
OMe,.0H HO.CMe% ~*~ HO.CMc OH ~ . ‘ 
A similar separation of HBr may be involved in the conversion, in 
presence of aluminium bromide, of propyl into isopropyl bromide 
CH,.CH,.CH,Br2 HBr + CH;.CH : CH,.2CH;.CHBr.CH, 
whilst in the conversion of «a into y-bromoacetoacetic ester the inter- 
mediate product would be a ring compound : 
CH 
CH, CO.CHBr.CO,Et? HBr + | *oH..CO,8t2.CH,Br.00.0H,.CO,Et. 
co 
2. Isomeric Change of Unsaturated Compounds.—This is merely 
another phase of the preceding case, for the isomeric change depends on 
association with H,O, H,SO,, or HBr, instead of on dissociation, and takes 
place under similar conditions. Thus the undecyclenes, like Butlerow’s 
octylenes, are in equilibrium in presence of sulphuric acid, the proportions 
being indicated in the equation ! 
(49) CH, : CH.CH,.C,H,;2 CH,.CHOH.CH,.C,H,,2CH,.CH : CH.C,H,, (96 %). 
At high temperatures changes of this type take place readily in contact 
with platinum black or alumina, for instance,? 
OH, 
cH, | 2OCH,.CH:CH,; 
\CH, 
under conditions such as these the conversion probably depends on asso- 
ciation with water, the activity of a trace of moisture being greatly 
increased by the high temperature and the presence of the contact 
substance. Isomeric changes of this kind are very frequent, especially 
amongst the terpenes. They may lead either to the shifting of a double 
bond, as in the conversion of dihydrocarvone into carvenone 
CO.CH 00.CH 
CH,.CHC : CHMe : CH, 2.CH,.CHZ No.cHMe, 
CH,.CH, \GH,.CH,” 
or to a rearrangement of the ring-system in the molecule, as when pinene 
1 Thoms and Mannich, Ber. 1903, 36, 2544. 
a Tanatar, Zeit. phys. Chem. 1902, 41, 735; Ipatieff and Huhn, Ber, 1903, 36, 
