Gas-phase measurements of the influence of stepwise solvation on the kinetics of SN2 reactions of solvated F− with CH3Cl and CH3Br and of solvated Cl− with CH3Br

1985 ◽  
Vol 63 (11) ◽  
pp. 3007-3011 ◽  
Author(s):  
Diethard K. Bohme ◽  
Asit B. Raksit
Keyword(s):  
Gas Phase ◽  
Room Temperature ◽  
Specific Rate ◽  
Flowing Afterglow ◽  
Phase Measurements ◽  
Sn2 Reactions ◽  
Energy Profiles ◽  
Nucleophilic Displacement ◽  
Displacement Reactions ◽  
Kinetics Of

Flowing afterglow measurements are reported which reveal the influence of stepwise solvation on the nucleophilicity of F− and Cl− in the gas phase at room temperature. The specific rates of nucleophilic displacement reactions with CH3Cl and CH3Br are followed for additions of up to three molecules of solvent for F− solvated with D2O, CH3OH, and C2H5OH and for Cl− solvated with CH3OH, C2H5OH, CH3COCH3, HCOOH, and CH3COOH. The observed precipitous response of the specific rate to solvation is attributed to intermediate features of plausible reaction energy profiles.

Gas-Phase Ion Chemistry of Siloxide and Silamide Ions by Using the Flowing Afterglow. Unusual Rearrangements Involving SiO and SiS Bond Formation

1989 ◽  
Vol 42 (4) ◽  
pp. 489 ◽  
Author(s):  
RAJ Ohair ◽  
JC Sheldon ◽  
JH Bowie ◽  
R Damrauer ◽  
CH Depuy
Keyword(s):  
Gas Phase ◽  
Exchange Reactions ◽  
Ion Chemistry ◽  
Simple Correlation ◽  
Flowing Afterglow ◽  
Gas Phase Ion Chemistry ◽  
Nucleophilic Displacement ◽  
Displacement Reactions ◽  
Gas Phase Ion ◽  
Sulfur Containing

Siloxide ions undergo O/S exchange reactions with suitable sulfur-containing neutrals, e.g. H3SiO-+CS2 → H3SiS-+COS. Silamide ions similarly undergo NR/O and NR/S exchange reactions together with nucleophilic displacement reactions, e.g. Me3SiNMe + CO2 → Me3SiO-+MeNCO →No simple correlation between rate and mechanism is observed for all the studied reactions.

Bridging the gap between the gas phase and solution: transition in the kinetics of nucleophilic displacement reactions

1981 ◽  
Vol 103 (4) ◽  
pp. 978-979 ◽  
Author(s):  
Diethard K. Bohme ◽  
Gervase I. Mackay
Keyword(s):  
Gas Phase ◽  
Nucleophilic Displacement ◽  
Displacement Reactions ◽  
Kinetics Of

Acid catalysis in the gas phase: dissociative proton transfer to formate and acetate esters

1979 ◽  
Vol 57 (22) ◽  
pp. 2996-3004 ◽  
Author(s):  
A. C. Hopkinson ◽  
G. I. Mackay ◽  
D. K. Bohme
Keyword(s):  
Proton Transfer ◽  
Gas Phase ◽  
Major Product ◽  
Flow Tube ◽  
Flowing Afterglow ◽  
Phase Measurements ◽  
Ion Flow ◽  
Intrinsic Kinetics ◽  
Selected Ion Flow Tube ◽  
Kinetics Of

The flowing afterglow and selected ion flow tube techniques are employed in gas-phase measurements of the intrinsic kinetics of protonation of methyl formate, n-propyl formate, ethyl acetate, and n-propyl acetate and subsequent fragmentation according to[Formula: see text]with R = H and CH3, R′ = CH3, C2H5, and (CH2)2CH3, and A = H2, CH4, CO, and H2O. Protonation by the acids, AH+, with relative strengths spanning a range of 65 kcal mol−1, is observed to proceed extremely rapidly with rate constants at 299 ± 2 K encompassing values of 2.9 to 8.5 × 10−9 cm3 molecule−1 s−1. Fragmentation is observed for HCOOCH3 only with the strongest acid, H3+, to produce CH3OH2+. For HCOO(CH2)2CH3, fragmentation is observed to produce C3H7+ with H3O+, and also HCOOH2+ with H3+. Little fragmentation of CH3COOC2H5 occurs with H3O+ but with H3+ the major product is CH3COOH2+ with smaller amounts of CH3CO+ and C2H5+. Proton transfer from H3O+ to CH3COO(CH2)2CH3 results in considerable dissociation to form CH3COOH2+. The fragmentation of these esters is discussed in terms of known reaction energetics and in terms of mechanisms for unimolecular acyl–oxygen, AAc1, and alkyl–oxygen, AA11, fission often invoked for analogous reactions in solution as well as modifications of these mechanisms which have been proposed in the context of recent gas-phase measurements.

An experimental study of the reactivity of the hydroxide anion in the gas phase at room temperature, and its perturbation by hydration

1981 ◽  
Vol 59 (11) ◽  
pp. 1615-1621 ◽  
Author(s):  
Scott D. Tanner ◽  
Gervase I. Mackay ◽  
Diethard K. Bohme
Keyword(s):  
Experimental Study ◽  
Proton Transfer ◽  
Gas Phase ◽  
Rate Constants ◽  
Room Temperature ◽  
Gas Phase Reactions ◽  
Flowing Afterglow ◽  
Hydroxide Anion

Flowing afterglow measurements are reported which provide rate constants and product identifications at 298 ± 2 K for the gas-phase reactions of OH− with CH3OH, C2H5OH, CH3OCH3, CH2O, CH3CHO, CH3COCH3, CH2CO, HCOOH, HCOOCH3, CH2=C=CH2, CH3—C≡CH, and C6H5CH3. The main channels observed were proton transfer and solvation of the OH−. Hydration with one molecule of H2O was observed either to reduce the rate slightly and lead to products which are the hydrated analogues of the "nude" reaction, or to stop the reaction completely, k ≤ 10−12 cm3 molecule−1 s−1. The reaction of OH−•H2O with CH3—C≡CH showed an uncertain intermediate behaviour.

The gas phase reactivity of the dimethylchloronium ion with alkylbenzenes

1981 ◽  
Vol 59 (15) ◽  
pp. 2412-2416 ◽  
Author(s):  
John A. Stone ◽  
Margaret S. Lin ◽  
Jeffrey Varah
Keyword(s):  
High Pressure ◽  
Gas Phase ◽  
Mass Spectrometer ◽  
Aromatic Hydrocarbons ◽  
Relative Rate ◽  
Ion Source ◽  
Nucleophilic Displacement ◽  
Rate Of Reaction ◽  
Displacement Reactions ◽  
Bonded Complexes

The reactivity of the dimethylchloronium ion with a series of aromatic hydrocarbons has been studied in a high pressure mass spectrometer ion source using the technique of reactant ion monitoring. Benzene is unreactive but all others, from toluene to mesitylene, react by CH3+ transfer to yield σ-bonded complexes. The relative rate of reaction increases with increasing exothermicity in line with current theories of nucleophilic displacement reactions.

Di-imide: Some Physical and Chemical Properties, and the Kinetics and Stoichiometry of the Gas-phase Decomposition

1973 ◽  
Vol 51 (21) ◽  
pp. 3605-3619 ◽  
Author(s):  
C. Willis ◽  
R. A. Back
Keyword(s):  
Gas Phase ◽  
Room Temperature ◽  
Chemical Properties ◽  
Phase Decomposition ◽  
Important Intermediate ◽  
Long Lifetime ◽  
Physical And Chemical ◽  
Text Formation ◽  
Kinetics Of

Preparation of di-imide by passing hydrazine vapor through a microwave discharge yields mixtures with NH3 containing typically about 15% N2H2, estimated from the gases evolved on decomposition. The behavior of the mixture (which melts at −65 °C) on warming from −196 to −30 °C suggests a strong interaction between the components. Measurements of magnetic susceptibility and e.p.r. experiments showed that N2H2 is not strongly paramagnetic, which with other observations points to a singlet rather than a triplet ground-state.Di-imide can be vaporized efficiently, together with NH3, by rapid warming, and the vapor is surprisingly long-lived, with a typical half-life of several minutes at room temperature. The near-u.v. (3200–4400 Å) absorption spectrum of the vapor was photographed; it shows well-defined but diffuse bands, with εmax = 6(± 3) at 3450 Å.Di-imide decomposes at room temperature in two ways:[Formula: see text][Formula: see text]Formation of NH3 was not observed but cannot be ruled out. The decomposition of the vapor is complicated by a sizeable and variable decomposition that occurs rapidly during the vaporization. The stoichiometry of this and the vapor-phase decomposition depends on total pressure and di-imide concentration. The kinetics of the decomposition of the vapor were studied from 22 to 200 °C by following the disappearance of N2H2 by absorption of light at 3450 Å, or the formation of N2H4 by absorption at 2400 Å, and by mass spectrometry. The kinetics are complex and can be either first- or second-order, or mixed, depending on surface conditions. The effect of olefin additives on the decomposition was studied, and is also complex.Mechanisms for the decomposition are discussed, including the possible role of trans-cis isomerization. The relatively long lifetime found for di-imide in the gas phase suggests that it may be an important intermediate in many reactions of hydronitrogen systems.

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