The Reactions of Alkoxide-Alkanol Negative Ions with Ketene. An ab initio and Ion Cyclotron Resonance Study

1985 ◽  
Vol 38 (3) ◽  
pp. 355 ◽  
Author(s):  
RN Hayes ◽  
JC Sheldon ◽  
JH Bowie
Keyword(s):  
Ab Initio ◽  
Cyclotron Resonance ◽  
Negative Ions ◽  
Ion Cyclotron Resonance ◽  
Reaction Sequence ◽  
Major Pathway ◽  
Stable Species ◽  
Product Ions ◽  
A Minor ◽  
Competing Reactions

Alkanol-alkoxide negative ions [RO----HOR] react with ketene to form stable species H-C≡C-O----HOR. The initial intermediate in the reaction sequence is produced by the formation of a hydrogen bond between the negatively charged oxygen of [RO----HOR] and a hydrogen of ketene. This intermediate decomposes by competing reactions, viz. ( i ) a minor pathway involving direct elimination of ROH, and (ii) a major pathway involving a rearrangement sequence. Intermediates and product ions have been defined by using ab initio calculations at the 4-31G level. The differences between the reactions of [RO----HOR]/ketene and [RO---- HOR]/acetaldehyde systems are discussed.

The reactions of alkoxide-alkanol negative ions with carbonyl compounds. An ion cyclotron resonance and ab initio study

1982 ◽  
Vol 35 (12) ◽  
pp. 2471 ◽  
Author(s):  
G Klass ◽  
JC Sheldon ◽  
JH Bowie
Keyword(s):  
Ab Initio ◽  
Carbonyl Compounds ◽  
Cyclotron Resonance ◽  
Negative Ions ◽  
Negative Ion ◽  
Reaction Pathways ◽  
Ion Cyclotron Resonance ◽  
Ab Initio Study ◽  
Reaction Sequence ◽  
Stable Product

Simple alkyl aldehydes, ketones and esters containing the unit >: CH-CO-react with alkoxide-alkanol negative ions [RO----HOR] to form stable [M+RO-] negative ions (neutral denoted by M). The initial intermediate in the reaction sequence is produced by the formation of a hydrogen bond between the negatively charged oxygen of [RO----HOR] and the hydrogen of the > >CH-CO- unit. This intermediate decomposes to the stable product ion by two reaction sequences: (i) by direct elimination of ROH, and (ii) by rearrangement to a decomposing 'doubly-solvated' negative ion in which the central hydrogen of [RO----HOR] and the hydrogen of the >CH-CO unit become identical. As both reaction pathways are complex, all intermediates and certain transition states have been properly defined by using ab initio calculations at the 4-31G level.

The reactions of [F----HOMe] and [MeCO2----HF] negative ions with acetaldehyde and acetone. An Ion Cyclotron Resonance and ab initio Study

1983 ◽  
Vol 36 (2) ◽  
pp. 289 ◽  
Author(s):  
JC Sheldon ◽  
JH Bowie
Keyword(s):  
Ab Initio Calculations ◽  
Ab Initio ◽  
Cyclotron Resonance ◽  
Methyl Formate ◽  
Negative Ions ◽  
Model System ◽  
Ion Cyclotron Resonance ◽  
Ab Initio Study ◽  
Mechanistic Pathway ◽  
System F

The ion [F-- - -HOMe] may be produced by the reaction of CF3O- with methyl formate, a reaction of a type widely used for the production of 'solvated' negative ions. The possible reaction mechanism for the model system F-/HCO2H has been explored by ab initio calculations. The reactions of acetaldehyde and acetone with [F-- - -HOMe] yield stable [M + F-] ions which are thought to correspond to 'solvated' enolate negative ions. Their formation in terms of a mechanistic pathway, recently proposed to account for the formation of [M + RO-] ions from [RO-- - -HOR]/ > CH-CO- systems, is supported by ab initio calculations.

Photodetachment of Negative Ions Using a Continuously Tunable Laser and an Ion Cyclotron Resonance Spectrometer

1971 ◽  
Vol 54 (6) ◽  
pp. 2758-2759 ◽  
Author(s):  
Kermit C. Smyth ◽  
Robert T. McIver ◽  
John I. Brauman ◽  
R. W. Wallace
Keyword(s):  
Cyclotron Resonance ◽  
Tunable Laser ◽  
Negative Ions ◽  
Ion Cyclotron Resonance ◽  
Ion Cyclotron

Ion Cyclotron Resonance Studies of Alkylsilyl Ions. II. The Reactions of Ketones, Carboxylic Acids and Esters with the Trimethylsilyl Cation

1979 ◽  
Vol 32 (6) ◽  
pp. 1389 ◽  
Author(s):  
IA Blair ◽  
JH Bowie
Keyword(s):  
Carboxylic Acid ◽  
Transition State ◽  
Lewis Acid ◽  
Cyclotron Resonance ◽  
Nucleophilic Attack ◽  
Ion Cyclotron Resonance ◽  
Deuterium Isotope Effect ◽  
Trimethylsilyl Cation ◽  
A Minor ◽  
Membered Transition State

Nucleophilic attack of a ketone, carboxylic acid or ester at the electrophilic centre of the trimethylsilyl cation (Me,Si+) produces a 1:1 adduct. This adduct does not decompose in the case of ketones. Acid adducts decompose primarily by loss of methane, but a minor pathway exists which involves elimination of a ketene. Ester adducts fragment primarily by this latter process through a four-membered transition state. The transfer of hydrogen was shown to arise solely from the acyl group and was shown to proceed with a small deuterium isotope effect. Further decomposition of the resulting ion by loss of methane provides unequivocal proof that esters react predominantly through the alkyl oxygen with the Lewis acid Me3Si+.

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