Rearrangements with retention of the carbon skeleton

Within each section, rearrangements of hydrocarbons are treated before those of compounds containing oxygen, nitrogen, halogen, or sulfur. 

In accord with the general principle laid down for this book, attention is focussed on the bonds that are broken or newly constituted on formal passage from a starting material to an end product. The material is arranged without regard to whether the reactions are intra- or inter-molecular and of whether they are of ionic or radical type. Specialist literature should be consulted on questions of reaction mechanism.33 

Wieland and Gornhardt6 allowed hydrogen chloride to react with dihydro-zymosteryl benzoate [5a cholest-8(9)-en-3/ -yl benzoate] in chloroform for 8 hours at room temperature and then isolated the cholest-8(13)-ene and -13(16)-ene derivatives from the reaction mixture. 

Hiinig and Eckardt7 found that the double bond wanders away from the end of the chain when 10-undecenoic acid is heated in 2N-potassium hydroxide solution in diethylene glycol at 200°, 50% of the acid being isomerized in 4.5 hours and 70% in 15 hours. 

1-Butene is isomerized within minutes when treated with potassium tert-butoxide in dimethyl sulfoxide at 55° 8 in this and other cases it has been observed that the isomerization leads preferentially to the thermodynamically less stable cw -isomer. 

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