Ion-molecule reactions in the gas phase. part XXII. Reactivity of the cis- and trans-indanediols with dimethyl ether ions

Specific reactivity of cis- and trans-indanediols has been investigated under dimethyl ether (DME) chemical ionization conditions. Several unusual species, such as [M + 29]+ and [M + 27]+ ions, are produced in high yield. From DME pressure variations and tandem mass spectrometry experiments (low-energy collisions with Ar and NH3) including some labeled compounds, it appears that [M + 29]+ ions are generated by nucleophilic substitution according to a SNi pathway from the proton bound[M + DMEH]+ adduct ion. On the other hand, [M + 27]+ ions are produced from the covalent [M + DME − H]+ adduct ions via a stepwise process inducing a water loss. This latter dehydration occurs from the adducts prepared by [DME − H]+ attachment to the homobenzylic hydroxy site, which allows internal proton transfer from the charged position to the benzylic hydroxy group, promotingthe loss of water. In addition, trans indanediol labeled with 18O has been used to obtain evidence for the regioselectivity of both water-loss mechanisms from the benzylic site.