Rate and Product Studies in the Solvolyses of Two Cyclic Phosphorochloridate Esters

Abstract

Kinetic and product studies of the solvolyses of acyclic phosphorochloridates are extended to two cyclic diesters, 2-chloro-1,3,2-dioxaphospholane-2-oxide (1) and 2-chloro-5,5-dimethyl-1,3,2-dioxaphosphorinane-2-oxide (2). Slightly faster solvolyses are observed for 1 than for the acyclic dimethyl phosphorochloridate (3), and 2 solvolyzes somewhat slower than 3. An extended Grunwald–Winstein equation treatment shows similar sensitivities to changes in solvent nucleophilicity and solvent ionizing power for 1, 2, and 3, and a concerted S_N2 attack is proposed in each case. Product studies for the solvolyses of 2 in aqueous alcohols are presented.

Keywords:

• Cyclic phosphorochloridates
• extended Grunwald–Winstein equation
• solvolysis

Acknowledgments

Presented, in part, at the 17th International Conference on Phosphorus Chemistry (ICPC-17), April 15–21, 2007, Xiamen, China, and briefly summarized in the proceedings of the conference: H. J. Koh, S. J. Kang, and D. N. Kevill, Phosphorus, Sulfur, and Silicon, 183, 364 (2008). H.J.K. thanks Chonju National University of Education for the granting of a sabbatical leave during the time that a portion of this research was carried out. Acknowledgment is made to the donors of the Petroleum Research Fund, administered by the American Chemical Society, for partial support of this research. D.N.K. thanks Professor H. Mayr (Universität München) for hospitality during the time this manuscript was being prepared.

Notes

^a Substrate concentration of 0.0065 mol dm⁻³.

^b Unless otherwise indicated, on a vol/vol basis, at 25.0°C, with the other component water.

^c With associated standard deviations.

^d From refs. 3 and 7.

^e From refs. 2 and 16.

^f Solvent prepared on a weight/weight basis.

^a With associated standard deviation.

^b Values at 25.0°C, from Table I, also used in the calculation; the activation parameters are accompanied by the standard error.

^c On a volume/volume basis at 25.0°C.

^d On a weight/weight basis.

^a With associated standard deviation.

^b Values at 50.0°C, from Table I, also used in the calculation; the activation parameters are accompanied by the standard error.

^c Calculated from the values at other temperatures, using the Arrhenius equation.

^d On a volume/volume basis at 25.0°C (the other component is water).

^a As defined in Eq. (3).

^b Aqueous ethanol and methanol on a volume/volume basis at 25.0°C and aqueous TFE on a weight/weight basis.

^c Molar percentage of ester formed in competition with the acid.

^d Values from ref. 10.

^e Only very small amounts of ester formed, and the S value was too low to be determined by the titration technique.

^a Number of data points.

^b From Eq. (1), and with associated standard error.

^c Multiple correlation coefficient.

^d From ref. 9.

^e From ref. 10.

^f From ref. 18.

^g This work.

^h From ref. 17.

ⁱ From ref. 11.

^a On volume/volume basis, except TFE-H₂O mixtures on a weight/weight basis.

^b The k(1) values from Table I, the k(2) values from Table III, and the k(3) values from ref. 10.