Four‐centred rearrangements in the mass spectra of aliphatic ethers

The [CH3OCHCH3]+ ions observed in the mass spectra of ethers of formula CH3OCH (CH3)R(R = H or alkyl) undergo two rearrangement fragmentation reactions to form [C2H5]+ and [CH2OH]+. The scope of the rearrangements has been investigated and it is shown that enlargement of the alkyl group on either side of the ether linkage leads to alternative fragmentation routes. From a study of metastable intensities it is concluded that the fragmentations probably occur directly from the [CH3OCHCH3]+ structure through four centred rearrangements rather than through the intermediacy of the [C2H5OCH2]+ ion.