A structure-reactivity study of selected phosphate esters

Bond, Dianne Ruth

A structure-reactivity study of selected phosphate esters

Doctoral Thesis

1985

Publisher

University of Cape Town

Department

Department of Chemistry

Faculty

Faculty of Science

Abstract

A comparative X-ray analysis study of bis(4-nitrophenyl)-8-quinolinyl phosphate (4), 1-naphthyl-bis(4-nitrophenyl) phosphate (5) and 4-nitrophenyl -8-quinolinyl phosphate (5) was undertaken. In compound (4) donor-acceptor nitrogen-phosphorus interactions change the geometry of the molecule from tetrahedral to quasi trigonal bipyramidal, thus the structure may be considered as an "early stage" of the intramolecular displacement of the 4-ni trophenoxide group. In the diester (6) this interaction is replaced by intermolecular N+ -H...O- hydrogen bonding. In addition the intramolecular non-bonded potential energies of (4) and (5) were calculated and the minimum-energy conformations were compared with those determined by X-ray diffraction. These results confirm the differences observed in the intramolecular interactions operative in (4) and (5). The mass spectra of (4) and (5) are dramatically different with respect to the fragmentation involving expulsion of the 4-nitrophenoxy radical and formation of the corresponding phosphorylitum ion by nitrogen participation. Rate measurements for the base-catalysed hydrolysis of the first P-OPNP linkage show that (4) is not significantly more reactive than (5) and provide no evidence for intramolecular nucleophilic catalysis in the hydrolysis of (4). The crystal and molecular structure of 1-naphthyl acetate (7) was determined. Attempts to grow suitable crystals of 8-quinolinyl acetate (8) failed and therefore its structure could not be elucidated. Possible intramolecular nitrogen - carbonyl carbon interactions operative in (8) could therefore not be established.

Description

Bibliography: pages 201-208.

Keywords

Physical Chemistry

Chemistry

Reference:

Collections

PhD / Doctoral

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