表面张力测定用于监测N-烷基全氟烷基磺酰胺的纯化

Measure of surface tension applied to monitor the purification of n-alkyl perfluoroalkanesulfonamides

N-烷基全氟烷基磺酰胺(RfSO2NHR,RfSO2NR2,Rf为全氟烷基,R为烷基)是一类重要的油溶性氟表面活性剂,通过全氟烷基磺酰氟和相应的胺制备。本文提供一种简单易行的纯化方法。将反应后的混合物首先经稀盐酸洗涤,除去未反应的胺,然后用去离子水洗涤。在水洗过程中,通过测定表面张力监控水洗过程:若水洗液的表面张力基本不再随水洗次数变化,则可判定杂质已经除去。以此可简单的检测N-烷基全氟烷基磺酰胺的纯化过程。该方法也可推广到其他多种类型的油溶性表面活性剂的纯化。以N-正丁基全氟辛基磺酰胺[CF3(CF2)7SO2NH(CH2)3CH3]的合成为例说明该反应后混合物经去离子水洗涤后水洗液的表面张力达到约53 mN/m后不再变化,判定杂质已除去,进一步通过红外、1HNMR、19FNMR、元素分析方法确认其结构。

N-Alkyl perfluoroalkanesulfonamides（RfSO2NHR and RfSO2NR2,in which Rf and R represent the perfluoroalkyl and alkyl groups,respectively） are an important category of fluorinated surfactants applied in organic solvents.They were prepared from perfluoroalkanesulfonyl fluoride and corresponding amines.A simple and convenient method of purification was provided in this work.The resulted mixture after reaction was washed with dilute hydrochloric acid to remove the amine that was not reacted.Then the raw product was washed by deionized water.The washing process was monitored by the measure of surface tension：if the surface tension of washing water was no longer changed with the times of washing,it denoted that the impurities were removed.Therefore,the purification process could be easily controlled.This method could be extended in the purification of other oil-soluble surfactants.The preparation of N-butyl perfluorooctanesulfonamide（C8F17SO2NHC4H9） was taken as an example.During the purification of product,the surface tension of washing water was increased to about 53 mN/m and no longer changed,which indicated that the removal of impurities was complete.The structure of purified product was further confirmed by IR,1HNMR,19F NMR and elemental analysis.