ON DYNAMIC ISOMERISM. 205 
The relative stability of the isomerides, depending as it does on the ratios 
of the velocities of change, is greatly influenced by substitution. The 
introduction of negative groups appears always to favour the production of 
the more acid isomeride. 
1. Ketones.—The mono-ketones are almost wholly ketonic, but their 
behaviour on bromination! and possibly their phosphorescence when 
exposed to Tesla radiation, or after exposure at low temperatures to ultra- 
violet light, indicates that even here a trace of enol may be present, The 
introduction of the CO,Et group in ethylic acctoacetate makes its chemical 
properties entirely different from those of acetone, but does not introduce 
any large proportion of enol into the equilibrium.” Amongst the 
diketones, however, ethyl acetylacetone, CH;,.CO.CHEt.CO.CH;, though 
almost wholly ketonic at 95°, contains about one-third of enol at 19° ; 
methyl acetylacetone, CH,.CO.CH.Me.CO.CH;, contains about one-eighth 
of enol at 96°, and one-half at 16°; whilst acetylacetone itself, 
CH,.CO.CH,.CO.CH,, contains about three-fourths of enol at 93° and 
at 17° appears to contain a certain amount of a dienolic form 
CH;.CO.CH,.CO.CH, 2 CH;.CO.CH : C(OH).CH; 2 
CH, :C(OH).CH : C(OH).CH, 
Similarly Claisen * found amongst the triketones an increasing tendency 
to enolisation, as benzoyl was displaced by acetyl in the series 
CHBz,, CHAcBz,, CHAc,.Bz, CH Ac. 
Camphor, like acetone, is almost wholly ketonic, though it yields an 
enolic benzoate, OHS | 
NO.OBz 
CHBr 
a-Bromocamphor,0sH,. | , is only known in the ketonic form, but the 
CO 
flash of light that appears when the crystals are crushed is perhaps 
an indication of the presence of a trace of the enolic form. 
CH.CO,Et, 
Hy, | 
‘co 
acetoacetate, is also mainly ketonic,’ but solutions of a-benzoyleamphor, 
a ee: 
CoH. | , contain 60 per cent. of the enolic isomeride.® 
co : 
, When boiled with benzoyl chloride.* 
Ethyl camphocarboxylate, C, the analogue of ethyl 
2. Aldehydes.—Enolisation of aldehyde only occurs when negative 
radicles are introduced into the methyl group, as in ethers of pheny!- 
formylacetic acid,’ 
oes oils 
H.CO.CH{  _ @HO.CH : C 
COR Nco.R 
and formylacetoacetic acid.® 
1 Lapworth, Trans. 1904, 85, 30. 2 Perkin, Zrans. 1892, 61, 801. 
3 Ann. 1896, 291, 25. 4 Lees, Zrans. 1903, 88, 152. 
5 Briihl, Ber. 1902, 35, 3510. 6 Forster, loc. cit. 
7 Wislicenus, Ann. 1896, 291, 147; Lapworth and Hann, Trans. Chem. Soc. 1502, 
81, 1491. 8 Ber, 1893, 26, 2730. ~ 
