J. P. Denhez

Intramolecular hydrogen atom abstraction with an eight-membered cyclic transition state in open-chain aliphatic aminium radicals

Abstract Hydrogen abstraction by the nitrogen in long-chain aliphatic gas-phase aminium radicals (amine molecular ions) takes place via six-, seven-, and eight-membered cyclic transition states. The subsequent fragmentation is particularly facile after eight-membered ring hydrogen transfer.

Reactions of silyl cations with ketones in the gas phase

In the gas phase, (CH(3))(3)SiOSi(+)(CH(3))(2) and (CH(3))CH(2)SiOSi(+)(CH(3))(2) ions 1 and 2 were formed in the external source of a Fourier transform ion cyclofrom resonance (FT-ICR) spectrometer by electron impact ionization of (CH(3))(3)SiOSi(CH(3))(3). In the FT-ICR cell, the electrophilic center of these ions reacts with acetone to give product ions whose structures are probed by comparison with those of the products formed by reaction with water. The mechanisms of formation of these products, studied by labeling, involve facile 1,3-methyl transfer from silicon to silicon and cyclic intermediates. Copyright 1999 John Wiley & Sons, Ltd.

Gas-phase reaction of acetaldehyde with silicon-containing ions

CH2=Si(CH3)OSi(CH3)2+ ions 1 were formed in the external source of a Fourier-transform ion cyclotron resonance (FT-ICR)mass spectrometer by fragmentation of (CH)3SiOSi(CH3)3. In the cell, their reactions with acetaldehyde were studied by using labeled reactants and compared with those with acetone, studied in previous work, which gives a general view of the reactions of ion 1 with carbonyl compounds. In contrast with the behavior of the corresponding carbon-containing ions, the results confirm facile 1,3-methyl group transfers from silicon to silicon. Otherwise, the silicon-containing adducts often eliminate C n H2n. This process, not observed in (C,O,H)-containing ions, is studied by using selectively deuterated reactants.

Gas phase reactions of silyl cations with water

Abstract In the gas phase, the (CH 3 )) 3 SSiOSi(CH 3 )) 2 + and (CH 3 )) 2 SSi + OOSi(CH 3 ))CH 2 ions were formed in the external source of a FT-ICR mass spectrometer by fragmentation of (CH 3 )) 3 SSiOSi(CH 3 )) 3 + . In the c. In the cell, the electrophilic center of these ions reacts with water to give product-ions which undergo, spontaneously or upon collision, sequential losses of methane and water. The reactions of D 2 OO and H 2 8 OO indicate that a permutation of the oxygen atom of the reactant and that of water takes place prior to the dissociation of the productions. This means that both oxygens play a symmetric role in an intermediate step of the reaction pathway.