Characterization of Transition States in Dichloro (1,4,7-Triazacyclononane) Copper (II)-Catalyzed Activated Phosphate Diester Hydrolysis

Authors

Kim A. Deal
Alvan C. Hengge, Utah State UniversityFollow
Judith N. Burstyn

Document Type

Article

Journal/Book Title

Journal of the American Chemical Society

Publication Date

1996

Volume

118

First Page

1713

Last Page

1718

Abstract

The reaction mechanism for Cu[9]aneN₃Cl₂-catalyzed hydrolysis of ethyl 4-nitrophenyl phosphate was probed using kinetic isotope effects and isotope exchange experiments. The solvent deuterium isotope effect (^Dk = 1.14), combined with the absence of ¹⁸O incorporation into 4-nitrophenol, suggests that hydrolysis proceeds through intramolecular attack of the metal-coordinated hydroxide at the phosphorus center. The secondary ¹⁵N isotope effect (¹⁵k = 1.0013 ± 0.0002) implies that loss of the leaving group occurs at the rate-limiting step with approximately 50% bond cleavage in the transition state. This study is one of the first applications of the secondary ¹⁵N isotope effect to simple metal-promoted hydrolysis reactions, and the result is consistent with concerted bond formation and cleavage. A mechanism consistent with the isotope studies is presented.

Recommended Citation

K. A. Deal, A. C. Hengge, J. N. Burstyn. “Characterization of Transition States in Dichloro (1,4,7- Triazacyclononane) Copper (II)-Catalyzed Activated Phosphate Diester Hydrolysis.” J. Am. Chem. Soc, 1996, 118, 1713-1718.