Structural Effects in Phosphates. 1. Comparison of 4-Nitrophenyl 1-Naphthyl and 4-Nitrophenyl Quinolin-8-yl Phosphates

Article abstract of DOI:10.1021/jo00213a017

Crystal and molecular structures of quinolin-8-yl bis(p-nitrophenyl) (4), quinolin-8-yl p-nitrophenyl (4a), and 1-naphthyl bis(p-nitrophenyl) phosphates (5) have been determined and compared.In 4 the donor-acceptor nitrogen-phosphorus interactions change the geometry of the molecule from tetrahedral to quasi-tbp, so the structure can be considered as an "early stage" of the intramolecular displacement of the PNPO group.In 4a this interaction is replaced by intramolecular N:H:O hydrogen bonding.The intramolecular nonbonded potential energies of 4 and 5 were calculated, and the minimum-energy conformations obtained were compared with those determined by X-ray diffraction.The results of calculations confirm the observed differences in the intramolecular interactions operating in 4 and 5.The mass spectra of 4 and 5 reveal a dramatic difference between these two phosphates with respect to the fragmentation involving the expulsion of the p-nitrophenoxy radical and the formation of the corresponding phosphorylium ion by the nitrogen atom.Rate measurements for the base-catalyzed hydrolysis of the P-OPNP linkage show that 4 is not significantly more reactive than 5 and provide no evidence for the intramolecular nucleophilic catalysis in the hydrolysis of 4.