Isomer-selected ion–molecule reactions of acetylene cations with propyne and allene

Abstract

One of the fundamental goals of chemistry is to determine how molecular structure influences interactions and leads to different reaction products. Studies of isomer-selected and resolved chemical reactions can shed...

Isotope-specific reactions of acetonitrile (CH3CN) with trapped, translationally cold CCl+

“…Unwanted ions were ejected from the trap by sweeping over resonance frequencies of the specific mass-to-charge ratio (m/z) of undesired ions. 43 This provided a clean sample of either CCl + or C 37 Cl + with minimal impurities, as demonstrated in Fig. 1.…”

“…The skimmed molecular beam was overlapped with a focused beam (216 nm) from a pulsed dye laser (LIOPTEC LiopStar; 10 ns pulse, 100 µJ/pulse) in the center of the trap. Non-resonant multiphoton ionization of TCE resulted in several frag- Cl + (hereafter, the more abundant isotope 35 Cl will be referred to as simply Cl, while 37 Cl will be specified when appropriate). Unwanted ions were ejected from the trap by sweeping over resonance frequencies of the specific mass-to-charge ratio (m/z) of undesired ions.…”

“…Additional higher order calculations were carried out at the CCSD(T)/CBS//CCSD/aug-cc-pVTZ level of theory for reactants and predicted products to provide accurate energetics for the thermodynamic limits of the reaction within 0.04 eV. Even though 37 Cl and D isotope substitutions were used experimentally to determine the chemical formulas of the products, calculations accommodating these substitutions are outside the scope of this work. Density functional theory (DFT) calculations and relaxed potential energy surface scans were done using Gaussian 16, 46 while the higher order MP2 and CCSD computations were done using Psi4 v1.3.2.…”

“…The cold, low-pressure environment provided by using a linear Paul ion trap (LIT) is excellent for elucidating ion-neutral chemical reactions. 31,32 This experimental setup affords a significant amount of control, including the manipulation of collisional energy, 33,34 nuclear spin, 35 and the measurement of isomer, 36,37 isotope, 38,39 and quantum state 40,41 dependencies. Ions of interest are co-trapped and sympathetically cooled with laser-cooled Ca + , forming a mixed species Coulomb crystal, achieving translationally cold, trapped ions.…”

Reactivity Trends in the Gas Phase Addition of Acetylene to N-protonated Aryl Radical Cations

“…Since all reactions have significantly exothermic addition pathways, and both reaction and product formation rates are essentially matched for each reaction, this points to a decisive kinetic bottleneck along the early stages of the reaction pathway. 40 As outlined in this section, it is possible to rationalise the kinetic trends of each target radical by considering the forward barrier to acetylene addition following the formation of a pre-reactive complex. A generalised scheme showing the key aspects of the pre-reactive complex formation and fate for 2Pyr + C2H2 is shown in Fig 8, Quantum chemical calculations for the entrance channel of each target radical encountering C2H2 were performed using M06-2X-D3(0)/6-31++G(2df,p) optimised geometries followed by DSD-PBEP86-NL/aug-cc-pVQZ single point energies.…”