英语翻译
Ionic liquids,which are also referred to as room temperature ionic liquids,room temperature molten salts(RTILs),organic ionic liquids,etc.refer to an ionic system which takes on a liquid state at the room temperature or slightly warmer.They are salts composed of organic nitrogen inorganic cations and inorganic anions [38–40].
As a promising class of new solvents,cation types of ionic liquids which have been studied (Fig.1) include:A) alkyl quaternary ammonium cation[NRXH4 .X]+; B) alkyl quaternary phosphonium cation [PRXH4 .X]+; C) N-alkyl pyridine cation[RPy]+; and D) N,N-2- alkyl imidazole cation[R1 R3im]+,in which im represents the imidazole structure,(if substituting group-R is at the 2-position,the structure would be indicated which is expressed with [R1R2Rim]+).As is shown in Fig.1,the cations are usually alkylsubstituted imidazole.Anions such as BF.4,PF.6,CF3 SO3 .,(CF3SO2) 2N.,C3F7CO0.,C4F9SO3 .,CF3COO.,ClO4 .can be used in combination with the above cations to form low melting point liquids [41].Most of the cations are 1-alkyl-3-methylimidazolium cations with the chemical structures as shown in Fig.2.The dissolution mechanismof cellulose in ionic liquids [42] involves the oxygen and hydrogen atoms of cellulose-OH in the formation of electron donor-electron acceptor (EDA) complexes which interact with the ionic liquid (Fig.3).For their interaction,the cellulose atoms serve as electron pair donor and hydrogen atoms act as an electron acceptor.In corresponding fashion,the cations in ionic
liquid solvents act as the electron acceptor center and anion as electron-donor center.