Reactions of CH3CHO*+ and of CH 3COH*+ with water upon Fourier transform ion cyclotron resonance conditions

Abstract : The reactions of CH3CHO+ and of CH 3COH+ with water yield the same products, at almost the same rate. It is shown, by using a characteristic reaction of the carbene structure, that a molecule of water converts CH3COH+ into its more stable isomer CH3CHO+, which is a new example of catalyzed 1,2-H transfer. The dominant product is the proton-bound dimer of water which, in fact, comes from the [H2OH+...CH 3] and [H2OH+...CO] primary products whose observed abundances are poor. In a related system, ionized formamide/water, a water molecule catalyzes the 1,3-transfer leading from the solvated carbene to the [H2O...H+...H2N-C=O ] stable intermediate, which eliminates CO without back energy. In contrast, such a process does not take place in the studied system since the cleavage of the so formed [H 2OH+...CH3CO] transient intermediate involves a high back energy; this is explained by the charge repartition within this intermediate. In fact, a different pathway takes place. The solvated acetaldehyde ion isomerizes into a terbody intermediate in which protonated water is bonded to a CO molecule on the one hand and to a methyl radical on the other hand. Simple cleavages of this complex yield the observed products.
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Submitted on : Wednesday, December 11, 2013 - 9:21:31 PM
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Hristo Nedev, Guillaume van der Rest, Philippe Mourgues, Henri Audier. Reactions of CH3CHO*+ and of CH 3COH*+ with water upon Fourier transform ion cyclotron resonance conditions. European Journal of Mass Spectrometry, IM Publications, 2003, 9 (4), pp.319. ⟨10.1255/ejms.564⟩. ⟨hal-00917378⟩

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