On the gas‐phase reaction of C₃O₂^+. with C₃O₂

Abstract

The gas-phase, ion molecule reaction between C,O:' and C,O, has been studied by both double-focusing and ion trap mass spectrometry, rationalized by the formation of a dimeric, odd electron cation IC6041+" which decomposes extensively through sequential CO losses giving rise to IC,O,l+. and IC,O,l+' ions. The thermodynamics of this process have been investigated by means of ab initio calculation performed on the above species using different basis sets (STO-3G, 3-21G and 6-31G*).t Present address:

Modeling the Chemistry of Gaseous Cations Derived from Tricarbon Dioxide

“…Ab initio computations have been reported for C 2 O + and for C 2 O +• and C 3 O +• . Pandolfo et al used HF and MP2/6-31G*, hypothesizing an unobserved acyclic dimeric ion C 6 O 4 +• as an intermediate undergoing sequential CO losses leading to C 5 O 3 +• and C 4 O 2 +• . (As discussed in Section , this intermediate and reactions 2 and 3 are not supported by the present work.…”

“…• is now found to be linear at its minimum E, a previous study using lower-level theory reported it as quasilinear C 2h . 12 For p even, the calculated electron spin density (Table S7) is nearly equal for all atoms, both C and O, indicating full delocalization of the unpaired electron occupying the highest, partially occupied MOs, π x 1 π y 0 . Spin for CO 2 +• is primarily on the O atoms, but for the other odd-p (3, 5, 7) ions, spin density is localized mainly on C atoms at the even positions.…”

“…Its E is 46.9 kJ/mol below that of the recalculated cyclo-C 3 isomer e + previously taken as the most stable. 12 Isomer d + has electron spin mainly at C3 (Table S2) with A(C2,C3,C4) = 143°, close to the angle at C2′ in a + . Isomer e + • contrary to experimental observations as argued above.…”

“…Each of these dimeric geometries a + −c + is at a local minimum E and stable with respect to dissociation, but since C 6 O 4 +• is not detected, if it is formed in a mass spectrometer, it must have a shorter lifetime than the approximately 1 μs minimum needed for detection. 12 As considered in the next section, it may not be produced here at all.…”

Quadrupole ion trap studies of fundamental organic reactions

“…For example, O'Hair (Reid et al, 1998, Reid, Simpson, & O'Hair, 1999 and Brodbelt (Felix, Reyzer, & Brodbelt, 1999) have demonstrated the ability of ion traps to do H/D exchange experiments with protonated peptides and nucleoside analogs, respectively. Traldi and co-workers have presented a series of ion trap studies focused on the gas-phase ion chemistry of carbon suboxide (Pandolfo et al, 1994(Pandolfo et al, , 1995Bortolini et al, 1999) as well as the reactions of unusual electrophilic ions formed during chemical ionization (Moneti et al, 1996(Moneti et al, , 1999Bortolini et al, 1998). In addition, Lovejoy (1999) has explored the reactions of protonated H 2 SO 4 /H 2 O clusters with small organic molecules and observed proton transfer as well as H 3 O þ transfer and hydride abstraction.…”