全氟和多氟型有机化合物的化学特性——全氟叔丁基碘以及全氟烷基的诱导效应顺序

CHEMISTRY OF THE PERFLUORO AND POLYFLUORO ORGANIC COMPOUNDS——PERFLUORO-t-BUTYL IODIDE AND THE INDUCTIVE ORDER OF PERFLUOROALKYL GROUPS

利用Krespan法合成全氟叔丁基碘(I),并证明它的结构.以溴代碘可进一步发展Krespan法,合成全氟叔丁基溴(II).碘化物(I)[或溴化物(II)]与二乙基胺或乙醇-氢氧化钾反应时,其第一步为亲核试剂直接对碘(或溴)原子进攻的类S2型反应,产物与由全氟异丁烯和有关试剂直接反应所得者相同.

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 SN2-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))_(3)CI,(CF_(3))_(2)CFI,and CF_(3)CF_(2)CF_(2)I.Theδ(H-B)values provide evidence for an electron-withdrawing inductive order for perfluoro alkyl groups such as:(CF_(3))_(3)C->(CF_(3))_(2)CF->CF_(3)CF_(2)->CF_(3)-.Arguments for the above order and against the generally accepted views are presented.