On the formation of C2H5O2+ ions having the structure of hydroxy-protonated acetic acid

Molecular Drivers of Base Flipping During Sequence‐Specific DNA Methylation

“…The metastable ion spectrum of m/z 72 ions shows a prominent peak at m/z 45 (HCS + ) corresponding to the loss of HCN. The kinetic energy release measured from the width at half‐height, T 0.5 , was found to be 1.27 meV, and this low value suggests that HCS + ion formation involves a direct bond‐cleavage reaction from hydrogen‐bridged ions or protonated hydroxyl group 23,28. Both the CID spectra display abundant peaks at m/z 71 (loss of H .…”

Protonated silanoic acid HSi(OH)2+ and its neutral counterpart: a tandem mass spectrometric and CBS‐QB3 computational study

“…On the other hand, direct bond cleavage reactions from ion–dipole and/or hydrogen‐bridged ions that dissociate at the thermochemical threshold typically have T 0.5 values <5 meV. A case in point21 is the loss of H 2 O from the metastable ions CH 3 C(OH) 2 + and CH 3 C(O)OH 2 + : the dissociation from CH 3 C(OH) 2 + involves a high–energy barrier and is associated with a large energy release ( T 0.5 = 300 meV), whereas the ion–dipole complex CH 3 C(O)OH 2 + loses H 2 O with a T 0.5 value of ∼1 meV. Thus, if the m / z 63 ions generated from I and II (see Scheme ) consist of a mixture of ions 1a + and 1b + , the above analysis predicts that the metastable peak for H 2 O loss would be a composite consisting of a fairly broad component, indicative of the dissociation of 1a + and a narrow component indicative of the dissociation of 1b + .…”

“…The elaborate computational study of Cheung and Li,20 which uses the Gaussian‐2 (G2) model chemistry, predicts that 2a + is the lowest energy isomer on the CH 3 O 2 + potential energy surface and that a substantial energy barrier separates the ion from its H‐shift isomer HC(O)OH 2 + , 2c + . The latter ion, unlike its methyl homologue CH 3 C(O)OH 2 + ,21 has not (yet) been experimentally characterized, but theory predicts it can easily communicate with the more stable proton‐bound dimer OC···H···OH 2 + , 2e + . The two ions may well serve as key intermediates in the two dissociations of low‐energy ions HC(OH) 2 + , 2a + , viz.…”

Structure, Thermochemistry and Reactivity of Protonated Glycolaldehyde

“…This ion has been claimed to be the origin of the loss of water observed from protonated acetic acid 19 and identified during a study of 2,4-dihydroxy-2-methylpentane. 20 We observe that, starting from [1Hd]…”