Iminium-ion formation and deuterium exchange by acetone in the presence of pyrrolidine, pyrazolidine, isoxazolidine, and their acyclic analogues

Journal Article · Tue Feb 26 23:00:00 EST 1980 · J. Am. Chem. Soc.; (United States)

DOI:https://doi.org/10.1021/ja00525a032· OSTI ID:5218656

Hine, J; Evangelista, R A

Equilibrium constants for iminium-ion-formation in the reaction of in acetone in aqueous solution at 35/sup 0/C with pyrazolidinium, isoxazolidinium, O,N-dimethylhydroxylammonium, and N,N'-dimethylhydrazinium ions were found to be 9.33, 8.96, 0.117, and 0.057 M/sup -1/, respectively. The kinetics of hydrolysis of the iminium ions were studied in every case except that of the N-isopropylidene-O,N-dimethylhydroxylammonium ion, whose hydrolysis is too fast to follow by the techniques used with the other iminium ions. The rate of hydrolysis of the N-isopropylidenepyrazolidinium ion is independent of the pH from about pH 3 to 6; it is hydrogen ion catalyzed at lower pHs and hydroxide ion catalyzed at higher pHs. The rate of hydrolysis of N-isopropylidenisoxazolidinium ions is Ph independent from pH 0.5 to about 2, increases until about pH 4, remains pH independent until pH 6.5, and has become too fast to measure above pH 8. Both reactions are general base catalyzed in all the buffers studied. A mechanism is described to fit the kinetics of each of these reactions. The dedeuteration of acetone-d/sub 6/ was studied pyridine buffers in the presence of each of the four hydrazine and hydroxylamine derivatives and also in the presence of the dimethylammonium and pyrrolidinium ion. All six of these secondary ammonium ions catalyze the dedeuteration by transforming the acetone-d/sub 6/ to an iminium ion that is dedeuterated by pyridine more rapidly than the ketone is. The iminium-ion formation is a relatively rapid equilibrium in all cases except that of pyrrolidinium ions, where the intermediate iminium ion loses deuterium and hydrolyzes at comparable rates, and possibly the case of dimethylammonium ions, where the amount of catalysis via iminium-ion formation is too small to reveal mechanistic details. The effect of structure on the efficiency of catalysis of dedeuteration via iminium-ion formation is discussed. 3 figures, 7 tables.

• Research Organization: Ohio State Univ., Columbus
• OSTI ID: 5218656
• Journal Information: J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 102:5; ISSN JACSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
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400303* -- Organic Chemistry-- Isotope Exchange & Isotope Separation-- (-1987)
ACETONE
AMINES
AZINES
AZOLES
CATALYSIS
CHEMICAL REACTION KINETICS
CHEMICAL REACTION YIELD
CHEMICAL REACTIONS
DECOMPOSITION
DEUTERIUM
EQUILIBRIUM
HETEROCYCLIC COMPOUNDS
HYDRAZINE
HYDROGEN COMPOUNDS
HYDROGEN ISOTOPES
HYDROLYSIS
HYDROXIDES
HYDROXYLAMINE
IMINES
ISOTOPES
ISOTOPIC EXCHANGE
KETONES
KINETICS
LIGHT NUCLEI
LYSIS
MEDIUM TEMPERATURE
NITROGEN COMPOUNDS
NUCLEI
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
OXYGEN COMPOUNDS
PH VALUE
PYRAZOLES
PYRAZOLINES
PYRIDINES
PYRROLES
PYRROLIDINES
REACTION KINETICS
SOLVOLYSIS
STABLE ISOTOPES
YIELDS