ISOMERIC CHANGE 623 



with water (or with sulphuric acid) in both of the two possible 

 ways : 



CH\ 

 CH 3 ;£ >CH.CH..OH 



CH/ 



Primary isobutyl alcohol 



Amylene and Amyl Alcohol. — Although this important obser- 

 vation was made in 1873, it was not until four years later that 

 Butlerow was able to make a clear pronouncement on the 

 subject of reversible isomeric change. The paper, " Ueber 

 Isodibutylen" (Annalen, 1877, ^9, 44-83), in which his views were 

 first fully developed, will always hold rank as a classic, and can 

 be regarded as second in value only to the papers in which 

 Liebig and Wohler announced their discoveries of isomerism 

 and of isomeric change half a century earlier. 



A part of the paper is devoted to observations on the 

 hydrocarbon amylene, C 5 H 10 , a compound intermediate in com- 

 plexity between isobutylene C 4 H 8 and isodibutylene C 8 H 16 . 

 Although very ready to undergo polymerisation, the hydro- 

 carbon could be prepared in a fairly pure form by heating 

 tertiary amyl alcohol in a sealed tube at ioo° with two or three 

 volumes of a mixture of equal weights of sulphuric acid and 

 water ; under these conditions it separated as an oil on the 

 surface of the acid, but when the mixture was allowed to cool 

 and shaken repeatedly, the oil re-dissolved in the acid (by 

 conversion into the alcohol or its sulphate), leaving only a 

 small residue of diamylene, C 10 H 20 , on the surface — 



HO . C(CH 3 ) 2 C(CH 3 ) 3 



I $ II -t-HX) 



CH,.CH 3 CH.CH 3 



Tertiary amyl alcohol Amylene 



By heating and cooling alternately these changes could be 

 repeated to any desired extent. In this way the reversibility 

 of the hydration and dehydration, postulated in the case of 

 isobutylene, was experimentally demonstrated as a general 

 action which might be assumed to take place to a greater or 

 less extent whenever an alcohol or an define was brought into 

 contact with a sulphuric acid of moderate strength. 



Isodibutylene. — Isodibutylene, the main subject of the memoir, 

 was prepared by the action of 50 per cent, sulphuric acid on 



