Structure, reactivity and thermochemical properties of protonated lactic acid. - École polytechnique Access content directly
Journal Articles Journal of Mass Spectrometry Year : 2004

Structure, reactivity and thermochemical properties of protonated lactic acid.

Abstract

The protonation energetics of lactic acid (LA) were experimentally determined by the kinetic method including the entropy effect. The values (proton affinity, PA(LA) = 817.4 +/- 4.3 kJ mol(-1); protonation entropy, DeltaS degrees (p)(LA) = -2 +/- 5 J K(-1) mol(-1); gas-phase basicity, GB(LA) = 784.5 +/- 4.5 kJ mol(-1)) agree satisfactorily with computed G2(MP2) expectations (PA(LA) = 811.8 kJ mol(-1); DeltaS degrees (p)(LA) = -7.1 J K(-1) mol(-1); GB(LA) = 777.4 kJ mol(-1)). The fragmentation behaviour of protonated lactic acid (LAH(+)) is dominated by carbon monoxide loss followed by elimination of a water molecule. Direct dehydration of LAH(+) is only a high-energy process hardly competitive with the CO loss. A complete mechanistic scheme, based on MP2/6-31G* calculations, is proposed; it involves isomerization of the various protonated forms of LA and the passage through the ion-neutral complex between the 2-hydroxypropyl acylium cation and a water molecule. Copyright 2004 John Wiley & Sons, Ltd.

Dates and versions

hal-00916221 , version 1 (09-12-2013)

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Cite

F. Berruyer-Penaud, Guy Bouchoux, Olivier Payen, Michel Sablier. Structure, reactivity and thermochemical properties of protonated lactic acid.. Journal of Mass Spectrometry, 2004, 39 (6), pp.613-620. ⟨10.1002/jms.627⟩. ⟨hal-00916221⟩
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