15520-32-8Relevant academic research and scientific papers
Acidity, basicity, and the stability of hydrogen bonds: Complexes of RO- + HCF3
Chabinyc, Michael L.,Brauman, John I.
, p. 10863 - 10870 (1998)
Ion-molecule complexes of RO- (R = Me, Et, i-Pr) and HCF3 have been studied with Fourier transform ion cyclotron resonance spectrometry. The RO- complexation energies with HCF3 were measured relative to RO-·H2O. These complexes, [ROHCF3]-, have complexation energies on the order of -20 kcal/tool and have low deuterium fractionation factors and are, therefore, hydrogen bonded. The structure of the complexes was studied by isotopic equilibrium experiments and ab initio calculations. All of the complexes studied have the structure RO-·HCF3 even when HCF3 is a stronger acid than ROH. The structure of the complexes can be understood through electrostatic arguments rather than the difference in acidity between the ion and neutral.
Bond strengths of ethylene and acetylene
Ervin, Kent M.,Gronert, Scott,Barlow,Gilles, Mary K.,Harrison, Alex G.,Bierbaum, Veronica M.,DePuy, Charles H.,Lineberger,Ellison, G. Barney
, p. 5750 - 5759 (1990)
Negative ion photoelectron spectroscopy and gas-phase proton transfer kinetics were employed to determine the CH bond dissociation energies of acetylene, ethylene, and vinyl radical: D0(HCC-H) = 131.3 ± 0.7 kcal mol-1, D0(CH2CH-H) = 109.7 ± 0.8 kcal mol-1, and D0(CH2C-H) = 81.0 ± 3.5 kcal mol-1. The strengths of each of the other CH and CC bonds in acetylene and ethylene and their fragments were derived. The energy required to isomerize acetylene to vinylidene was also determined: HC≡CH → H2C=C: ΔHisom,0 = 47.4 ± 4.0 kcal mol-1. As part of this study, proton transfer kinetics in a flowing afterglow/selected-ion flow tube apparatus were used to refine the acidities of ethylene, acetylene, and vinyl. The gas-phase acidity of acetylene was tied to the precisely known values for hydrogen fluoride, ΔGacid,298(HF) = 365.6 ± 0.2 kcal mol-1, and water, ΔGacid,298(H2O) = 383.9 ± 0.3 kcal mol-1, yielding ΔGacid,298(HCC-H) = 369.8 ± 0.6 kcal mol-1. The gas-phase acidity equilibria of acetylene with isopropyl alcohol and tert-butyl alcohol were also measured. Combined with relative acidities from the literature, these measurements yielded improved acidities for the alcohols, ΔGacid,298((CH3)2CHO-H) = 370.1 ± 0.6 kcal mol-1, ΔGacid,298((CH3)3CO-H) = 369.3 ± 0.6 kcal mol-1, ΔGacid,298(C2H5O-H) = 372.0 ± 0.6 kcal mol-1, and ΔGacid,298(CH3O-H) = 375.1 ± 0.6 kcal mol-1. The gas-phase acidity of ethylene was measured relative to ammonia, ΔGacid,298(NH3) = 396.5 ± 0.4 kcal mol-1, giving ΔGacid,298(C2H4) = 401.0 ± 0.5 kcal mol-1. The gas-phase acidity of vinyl radical was bracketed, 375.1 ± 0.6 kcal mol-1 ≤ ΔGacid,298(CH2C-H) ≤ 380.4 ± 0.3 kcal mol-1. The electron affinities of ethynyl, vinyl, and vinylidene radicals were determined by photoelectron spectroscopy: EA(HCC) = 2.969 ± 0.010 eV, EA(CH2CH) = 0.667 ± 0.024 eV, and EA(CH2C) = 0.490 ± 0.006 eV.
Generation, Thermodynamics, and Chemistry of the Diphenylcarbene Anion Radical (Ph2C.-)
McDonald, Richard N.,Gung, Wei Yi
, p. 7328 - 7334 (2007/10/02)
Dissociative electron attachment with Ph2C=N produced Ph2C.- (m/z 166).The reactions of Ph2C.- with potential proton donors of known gas-phase acidity were used to bracket PA(Ph2C.-) = 380 +/- 2 kcal mol-1 from which ΔHf0(Ph2C.-) = 81.8 +/- 2 kcal mol-1 was calculated.The reactions of Ph2C.- with CH3OH and C2H5OH proceeded with major and minor amounts, respectively, of a H2.+-transfer channel, forming Ph2CH2, RCHO, and an electron.The kinetic nucleophilicity of Ph2C.- in SN2 displacement reactions with CH3X and C2H5X molecules was shown to be medium, which requires a significant intrinsic barrier in these reaction.The reactions of Ph2C.- with various aldehydes, ketones, and esters were fast and established two principal product-forming channels: (1) H+ transfer if the neutral reactant contains activated C-H bonds and (2) carbonyl addition followed by radical β-fragmentation of one of the groups originally attached to the carbonyl carbon.The order for the ease of radical β-fragmentation in the tetrahedral intermediates was RO > alkyl >> H, and CO2CH3 > CH3.Since the reactions of Ph2C.- with the simple esters HCO2CH3 and CH3CO2CH3 were fast, it should now be possible to examine the reactions of carbonyl-containing organic molecules, which are expected to react slower than these esters and obtain their relative reactivities.
Gas-Phase Elimination Reactions of Ethers Induced by Amide and Hydroxide Ions
DePuy, C.H.,Bierbaum, Veronica M.
, p. 5034 - 5038 (2007/10/02)
The flowing afterglow technique has been employed to study the gas-phase reactions of a series of dialkyl ethers with amide and hydroxide ions.Ethers with β-hydrogens react rapidly by elimination rather than substitution mechanisms, and they demonstrate considerable specificity in the direction of elimination.With amide ion elimination proceeds primarily by removal of the most acidic hydrogen with little or no evidence of alkoxide stability playing a role.With hydroxide ion as the base the stability of the leaving groups appears to be of some importance, and cluster ions between water and the alkoxide ions are the major products.Evidence is presented for a long-lived complex of reaction products which can react further before separating.
