A DFT evaluation of molecular reactivity of volatile organic compounds in support of chemical ionization mass spectrometry

Gas phase H+, H3O+ and NH4+ affinities of oxygen-bearing volatile organic compounds; DFT calculations for soft chemical ionisation mass spectrometry

“…All quantum chemistry calculations are carried out using ORCA 5.0.1 software. 42 Molecular geometries of all neutral reactant molecules, their protonated forms and the adduct ion forms were first drawn using AVOGADRO 43 software and then further optimised using ORCA with the B3LYP hybrid functional using 6-311++G(d,p) basis set (somewhat wider than 6-31+G(d,p) used previously 39 ) and additionally with the D4 correction. 44 This level of theory was also used to calculate the normal mode vibrational frequencies and thermodynamic quantities of the neutral molecules and the ion structures.…”

“…34,35 Several studies were recently carried out in an attempt to predict PA of organic molecules using ab initio or DFT computational approaches. [36][37][38] Additionally, PA was calculated for indole 39 as a benchmark using ab initio MP2 (Moller-Plesset with second-order energy correction) and DFT with two functionals B3LYP and M06-2X and five different basis sets to compare their agreement with available experimental values revealing that B3LYP is optimal in terms of computational cost and accuracy, even with a relatively restricted basis set 6-31+G(d,p). PA and IE were then calculated for several classes of molecules using this level of theory.…”