Halides and the carbon-carbon double bond: Interactions of ethylene with bromide and iodide

Halide–propene complexes: validated DSD-PBEP86-D3BJ calculations and photoelectron spectroscopy

“…These neutral interactions can also be compared to those of previously studied halide-alkene systems, namely the halide–ethene complexes. 26 In these complexes, where the interaction dominated by the perturbation of the π-system, the strength of interaction is lower than when a purely hydrogen bonding environment is available. The E stab values for the halide–ethene complexes are 0.21 eV (19.5 kJ mol −1 ) and 0.13 eV (12.6 kJ mol −1 ) for bromide and iodide respectively.…”

“…21,22 The complexes selected are the halide complexes with O 2 , N 2 , acetylene, ethene and both the syn-and anti-formic acid isomers. 17,20,[23][24][25][26][27] As these complexes have been investigated previously, starting geometries were chosen from those already optimised using ab initio methods rather than a traditional search of conformer space.…”

Spectroscopic Study of the Br−+CH3I→I−+CH3Br SN2 Reaction

“…Using computational methods such as ab initio calculations, it is possible to determine vertical detachment energies (VDE) that can be compared to experimental photodetachment peaks in a photoelectron spectrum, based on an optimised chemical structure. The Wild group has previously utilised anion photoelectron spectroscopy in conjunction with high‐level CCSD(T) calculations to elucidate the structure and binding motifs of van der Waals complexes observed in the gas‐phase, with good agreement to experimental data [28,29,38–40] …”

“…The $${{{\rm e}}_{{\rm B}{\rm E}}}$$ can yield information about intermolecular interaction strength of a van der Waals complex. For example, the $${{{\rm \ }}^{2}{{\rm P}}_{3/2}}$$ and $${{{\rm \ }}^{2}{{\rm P}}_{1/2}}$$ photodetachment peaks in a bare bromide spectrum can be found at approximately 3.36 eV and 3.82 eV respectively, [37] however upon complexation with a molecule the two photodetachment peaks shift to higher energy [38–40] . This shift in binding energy relative to the bare nucleophile is called a stabilisation energy ($${{E}_{stab}}$$ ) and is indicative of the strength of the intermolecular forces binding the complex.…”

“…The Wild group has previously utilised anion photoelectron spectroscopy in conjunction with high-level CCSD(T) calculations to elucidate the structure and binding motifs of van der Waals complexes observed in the gas-phase, with good agreement to experimental data. [28,29,[38][39][40] In this study, we present the photoelectron spectrum assigned to the S N 2 reaction intermediates Br À � � � CH 3 I and I À � � � CH 3 Br, formed from the bare constituents Br À and CH 3 I. The pre-reaction and post-reaction adducts of the S N 2 reaction were observed and identified using a combination of mass spectrometry, anion photoelectron spectroscopy, and high-level CCSD(T) calculations.…”