Anionic migration effected by collisional activation. Hydride ion mobility in keto substituted alkoxide anions

Keto alcohols of the formula MeCO(CH2)nOH (n = 3–5) are deprotonated by HO− at both –OH or α to the carbonyl group. The various deprotonated species interconvert under the conditions of collisional activation. The fragmentations of (M–H)− ions are varied and complex, with most fragmentations being directed from the alkoxide centre. These fragmentations have been investigated by product ion and deuterium labelling studies. An interesting hydride transfer reaction occurs when n = 3 and 4, i.e. H− transfer occurs from the CH2 group next to the alkoxide centre to the carbon of the carbonyl group to form −CH2CHO as the product anion. This reaction does not occur when n = 5. The corresponding Me− transfer from deprotonated MeCO(CH2)n–1C(Me)2OH (n = 2 and 3) is not observed.