Ion-Cyclotron Resonance Studies of Alkylsilyl Ions. I. The Reactions Between Alcohols and the Trimethylsilyl Cation

1979 ◽  
Vol 32 (1) ◽  
pp. 59 ◽  
Author(s):  
IA Blair ◽  
G Phillipou ◽  
JH Bowie
Keyword(s):  
Proton Transfer ◽  
Transition State ◽  
Cyclotron Resonance ◽  
Nucleophilic Attack ◽  
Ion Cyclotron Resonance ◽  
Trimethylsilyl Cation ◽  
Ion Cyclotron ◽  
Decomposition Pathway ◽  
Membered Transition State

Nucleophilic attack of an alcohol (ROH) at the electrophilic silicon centre of the trimethylsilyl cation (Me3Si+) produces the 1 : 1 adduct Me3-O+(H)R(1). The adduct may fragment by loss of methane to yield Me2Si+-O-R; and this elimination is most pronounced when R = Me. When R ≥ C2H5, the major decomposition pathway of (1) involves elimination of the alkene [R-H] to produce Me3Si-O+H2, which may undergo further reaction with the neutral alcohol to reform (1). The proton transfer which accompanies the elimination of [R- H] from (1) originates predominantly from C2 of the alcohol; this suggests the intermediacy of a four-membered transition state in this reaction.

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+.

Proton transfer as a first step in ion-molecule reactions of diethyl ether and tetrahydrofuran

1976 ◽  
Vol 29 (8) ◽  
pp. 1837
Author(s):  
T McAllister
Keyword(s):  
Proton Transfer ◽  
Mass Spectrometer ◽  
Diethyl Ether ◽  
Cyclotron Resonance ◽  
Double Resonance ◽  
Ion Cyclotron Resonance ◽  
Ion Molecule Reactions ◽  
Ion Cyclotron

Mechanisms may be written for several of the ion-molecule reactions in tetrahydrofuran and diethyl ether for which the first step is protonation to give the ion (M+l)+. This hypothesis was tested inan ion cyclotron resonance mass spectrometer by double-resonance experiments on mixtures of each of the ethers with methane. It was shown that CH5+ is a precursor for the tetrahydrofuran reactions,but not, with one exception, for the diethyl ether reactions.

scholarly journals Fourier transform ion cyclotron resonance MS reveals the presence of a water molecule in an enzyme transition-state analogue complex

2004 ◽  
Vol 101 (43) ◽  
pp. 15341-15345 ◽  
Author(s):  
C. H. Borchers ◽  
V. E. Marquez ◽  
G. K. Schroeder ◽  
S. A. Short ◽  
M. J. Snider ◽  
...  
Keyword(s):  
Fourier Transform ◽  
Water Molecule ◽  
Transition State ◽  
Cyclotron Resonance ◽  
Ion Cyclotron Resonance ◽  
Transition State Analogue ◽  
Ion Cyclotron
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