Mass spectral hydrogen rearrangements of 1,1′‐bicycloalkyldiols under electron impact

1,1′‐Bicycloalkyl‐2,2′‐diols (mixtures of stereoisomers) and 1,1′‐diols on electron impact give rise to strong peaks equivalent to [M‐1]⁺ions, corresponding to cycloalkenone fragments and obviously involving hydrogen atom migrations. Deuterium labelling and substitution techniques reveal the operation of different rearrangement mechanisms for the two series of isomeric compounds. Thus, in the 1,1′‐bicycloalkyl‐2,2′‐diols a ring hydrogen atom is involved in the rearrangement, whereas in the 1,1′‐bicycloalkyl‐1,1′‐diols (pinacols) the hydroxylic hydrogen atoms migrate.