CHEMISTRY OF THE PERFLUORO AND POLYFLUORO ORGANIC COMPOUNDS——PERFLUORO-t-BUTYL IODIDE AND THE INDUCTIVE ORDER OF PERFLUOROALKYL GROUPS
CHEN Ching-Yun; JIANG Hsi-Kwei; CHEN Bing-Qi; LIANG Meng-Lan Institute of Organic Chemistry, Academia Sinica
Perfluoro-t-butyl iodide (I) was synthesized by the application of the method of Krespan. It was found that this method can be extended by the use of bromine in place of iodine for the synthesis of the corresponding bromide (II). The first step in the reactions of the iodide (I) with diethyl amine and ethanolic potassium hydroxide is shown to involve an S_N2-like attack on the iodine atom by the nucleophile. The products of the above reactions were identical with those from the reactions between perfluoro-isobutene and the corresponding nucleophiles. Ultraviolet solvent shifts, δ(H-B), were determined for (CF_3)_3CI, (CF_3)_2CFI, and CF_3CF_2CF_2I. The δ(H-B) values provide evidence for an electron-withdrawing inductive order for perfluoro alkyl groups such as: (CF_3)_3C-(CF_3)_2CF-CF_3CF_2-CF_3-. Arguments for the above order and against the generally accepted views are presented.