From measurements of the chloride-36 exchange rate with various RPOCU compounds and spectroscopic determination of the donor strength of various phosphoryl compounds, it has been possible to examine the electronic effects present in bimolecular displacement reactions on four-coordinate phosphorus. The exchange reaction with RPOCh compounds has been shown to follow secondorder kinetics in the solvent 1,2-dichloroethane at -30°.The effect of substituent is to decrease the rate in the order C6tf5 > CH3 > OCH3 ~Cl > OC,Hb. The effect of substituent on the donor strength of the phosphoryl oxygen gives rise to the order (CH^N ~C3H5 > CH% > OCH3 > OC3Hs, > Cl.The relative importance of inductive and conjugative effects for these substituents has been discussed. These studies aid in the interpretation of some previously published n.q.r. data. Interpreting the donor strength(1) (a)
We have modified a standard Aminco-Bowman spectrophotofluorometer to allow collection of spectral data on punched paper tape. Using this tape, we have obtained high quality corrected spectra by postprocessing techniques on a digital computer. We have examined the errors associated with changes in the energy distribution of the excitation source.
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