16331-64-9Relevant academic research and scientific papers
INFRARED STUDY OF THE ADSORPTION OF ETHYL ACETATE ON RUTILE
Graham, John,Rochester, Colin H.,Rudham, Robert
, p. 1973 - 1980 (1981)
Infrared spectra of ethyl acetate adsorbed on rutile at the solid/vapour interface are reported.Dissociative chemisorption gave surface acetate and ethoxide ions.Reactions involving surface hydroxyl groups generated acetic acid which was weakly adsorbed and could be removed by evacuation at room temperature.The relative reactivities towards ethyl acetate of four types of hydroxyl group characterized by distinguishable infrared bands are discussed.Hydroxyl groups responsible for a maximum at 3410 cm-1 are inaccessible to organic adsorbates an possibly exist at sub-surface lattice sites.Spectra of acetic acid adsorbed on rutile are briefly reported.
Acidity, basicity, and the stability of hydrogen bonds: Complexes of RO- + HCF3
Chabinyc, Michael L.,Brauman, John I.
, p. 10863 - 10870 (2007/10/03)
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.
Gas-Phase Nucleophilic Displacement Reactions
Olmstead, William N.,Brauman, John I.
, p. 1653 - 1662 (2007/10/03)
Displacement reactions of each of a variety of anionic nucleophiles reacting with each of a variety of neutrals have been studied by pulsed ion cyclotron resonance (ICR) spectroscopy.Rate constants for these reactions are interpreted in terms of a three-step reaction sequence.RRKM calculations are used to obtain information about the energy of transition states.The origin of the barrier to reaction in solution is discussed.
Reaction Rates of Trimethylethoxysilane and Trimethylmethoxysilane in Alkaline Alcohol Solutions
Jaeglid, Ulf,Lindqvist, Oliver
, p. 887 - 891 (2007/10/02)
The kinetics of the reaction (CH3)3SiOC2H5 + CH3O- (CH3)3SiOCH3 + C2H5O- have been investigated in both directions by means of FTIR spectroscopy.To obtain k1, trimethylethoxysilane was reacted with methoxide in a metha
Trimethylphosphine: Anion-Molecule Reactions and Acidity in the Gas Phase
Grabowski, Joseph J.,Roy, Paul D.,Leone, Robert
, p. 1627 - 1632 (2007/10/02)
Gas-phase acidity of trimethylphosphine has been investigated at ambient temperature by examining proton-transfer reactions in 40 Pa of helium buffer gas in a Flowing Afterglow instrument.On the basis of the occurence-non-occurence of a number of proton-transfer reactions and the observation of rapid H-D exchange between D2O and the conjugate base of trimethylphosphine, it has been determined that trimethylphosphine is more acidic than water.Quantitative measurements are reported for the reaction of trimethylphosphine with atomic oxygen anion and methoxide.These latter two anions exhibit multiple reaction pathways, one of which is proton transfer.From measurements of the rate coefficients of these two reactions and the relative product yields, it is concluded that the gas-phase acidity of trimethylphosphine is very similar to that of the hydroxyl radical; the recommended value is ΔGoacid(PMe3) 1577 +/- 13kJ mol-1.The derived acidity measurement is in slight contrast to recent theoretical and experimental estimates.Furthermore, it is found that anions which react only slowly with trimethylphosphine by proton transfer can undergo an alternative reaction which corresponds to addition of the neucleophilic anion to trimethylphosphine followed by loss of methane.
On the Mechanism of Base-Induced Gas-Phase Elimination Reactions of Ethers
Koning, Leo J. de,Nibbering, Nico M. M.
, p. 1715 - 1722 (2007/10/02)
For the base-induced gas-phase elimination reactions of diethyl ether and cis- and trans-1-tert-butyl-4-methoxy-cyclohexane the kinetic isotope and leaving group effects have been determined as functions of the base strength using the method of Fourier transform ion cyclotron resonance mass spectrometry.The results are interpreted in terms of a variable E2 transition-state structure.Increasing the base strength causes the transition state to shift toward the carbanion or E1cb region of the E2 spectrum, which is also a general phenomenon in the condensed phase.Moreover, it appears that the elimination reactions most readily proceed via a transition state in which the β hydrogen and leaving group are periplanar.If the substrate does not easily allow such a relationship, the transition state is found to shift toward the carbenium ion or E1 region of the E2 spectrum where the geometric restrictions of the substrate are less perceptible.The concept of syn/anti dichotomy is used to explain the formation of tree and solvated alkoxide anions in the reactions induced by OH-.Anti elimination is believed to result in the formation of free alkoxide.Syn elimination, which takes advantage of the electrostatic interaction between the base and leaving group, is held responsible for the formation of solvated alkoxide.The importance of base/leaving group association in the transition state of the syn elimination is demonstrated by the low yield of solvated alkoxide in the reaction of OH-, solvated by a dimethylamine molecule, with diethyl ether.Finally, it seems that the selectivity of gas-phase elimination reactions is determined by not only the relative heights of the intrinsic reaction barriers, but also the relative stabilities of the ion/molecule complexes preceding the reaction barriers.
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.
The Four-centre Reactions of Alkanol-Alkoxide Negative Ions with Alkyl Ethers and Orthoacetates. An Ion Cyclotron Resonance Study
Hayes, Roger N.,Paltridge, R. Lee,Bowie, John H.
, p. 567 - 572 (2007/10/02)
Alkoxide-alkanol negative ions 1O-...HOR2> react with carbon ethers (e.g., Me3COR3) by the four-centre reactions 1O-...HOR2> + Me3COR3 -> 2O-...HOR3> + Me3COR1, and 1O-...HOR2> + Me3COR3 -> 1O-...HOR3> + Me3COR2.The former reaction predominates when R1 2.In the case of di- and tri-ethers, the four-centre reaction can, in principle, compete with the alternative six-centre reaction.For example, for Me2C(OR3)2, 1O-...HOR2> + Me2C(OR3)2 -> Me2C=O + R1OR3 + 2O-...HOR3>.Evidence is presented which shows that the six-centre reaction does not occur.
