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Separation by /sup 23/Na NMR of the unimolecular and bimolecular components of the dissociation kinetics of 18-crown-6-Na/sup +/ in some nonaqueous solvents

Journal Article · · J. Am. Chem. Soc.; (United States)
DOI:https://doi.org/10.1021/ja00226a016· OSTI ID:5837394
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The kinetics of dissociation of (18-crown-6, Na/sup +/)/sup 1/ in propylene carbonate (PC), acetonitrile (AN), pyridine (PY), and acetone (AC) have been determined by /sup 23/Na NMR. Two mechanisms of exchange, namely unimolecular dissociative and bimolecular, have been shown to be in competition in the first three solvents. In acetone, the exchange mechanism is almost exclusively unimolecular. The activation parameters for the unimolecular exchange have been determined in all four solvents. /Delta/H/sub uni//sup /double dagger// follows the trend AN < AC < PY /approx equal/ PC. A compensation effect between /Delta/H/sup /double dagger// and /Delta/S/sup /double dagger// was observed. As a result, /Delta/G/sub 300K//sup /double dagger// is in the range 50-58 kJ/center dot/mol/sup /minus/1/ (AC and PY, respectively). No direct relationship between the Gutmann donicity number and /Delta/G/sup /double dagger// or /Delta/H/sup /double dagger// could be established, showing that several factors, including conformational rearrangement of the ligand and reorganization of the solvent cage, contribute to the barrier of exchange. The activation parameters were also determined for the bimolecular exchange mechanism in PC: /Delta/H/sub bi//sup /double dagger// = 35 /plus minus/ 1 kJ/center dot/mol/sup /minus/1/ and /Delta/S/sub bi//sup /double dagger// = /minus/16 /plus minus/ 3 J/center dot/K/sup /minus/1//center dot/mol/sup /minus/1/.

Research Organization:
Ottawa-Carleton Chemistry Institute, Ontario (Canada)
OSTI ID:
5837394
Journal Information:
J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 110:18; ISSN JACSA
Country of Publication:
United States
Language:
English

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Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400105 -- Separation Procedures
400201* -- Chemical &amp; Physicochemical Properties
ACETONE
ACETONITRILE
ACTIVATION ENERGY
ALCOHOLS
ALKALI METAL COMPOUNDS
ALKALI METAL ISOTOPES
AZINES
CARBONIC ACID ESTERS
CHEMICAL REACTION KINETICS
DATA
DISSOCIATION
DISSOCIATION HEAT
ENERGY
ENTHALPY
ESTERS
EXPERIMENTAL DATA
GLYCOLS
HETEROCYCLIC COMPOUNDS
HYDROXY COMPOUNDS
INFORMATION
ISOTOPES
KETONES
KINETICS
LIGHT NUCLEI
MAGNETIC RESONANCE
NITRILES
NMR SPECTRA
NUCLEAR MAGNETIC RESONANCE
NUCLEI
NUMERICAL DATA
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANIC POLYMERS
PHYSICAL PROPERTIES
POLYETHYLENE GLYCOLS
POLYMERS
PYRIDINE
PYRIDINES
REACTION HEAT
REACTION KINETICS
RESONANCE
SODIUM 23
SODIUM COMPOUNDS
SODIUM ISOTOPES
SOLVENT PROPERTIES
SPECTRA
STABLE ISOTOPES
THERMODYNAMIC PROPERTIES
THERMODYNAMICS