High-Field Rapid Injection NMR: Observation of Unstable Primary Ozonide Intermediates

Article abstract of DOI:10.1021/jo00197a027

A "rapid injection" NMR system is described for use on a 360-MHz superconducting spectrometer.The major advantages of the high-field sytem over our original system are increased sensitivity, resolution, and rapidity.The technique was used to study the ozonolysis of tetramethylethylene and (briefly) cis-but-2-ene, particularly the decomposition of the corresponding primary ozonides 2 and 4, with half-lives of 0.74 and 0.06 s, respectively, at -92 deg C.It was found that the decomposition of 2 in CD2Cl2 (a) had Δ H(excit) = 39 kJ/mol and Δ S(excit) = 28 J/(molK), (b) was unaffected by the presence of TCNE, but (c) was acid-catalyzed.The effects of substituents, solvent, and acid catalysts on the decomposition of primary ozonides are discussed.