Study On The Interactions Of Ionic Liquid With P-aminophenol And Hydroquinone

Phenolic compounds are an important class of chemical and pharmaceutical intermediates,which have a wide range of applications in many fields,leading to the presence of phenols in industrial waste water,causing irreversible damage to the environment and human body.Therefore,the detection of phenols in water has attracted comprehensive attention.The molecular structures of p-aminophenol hydrochloride?PAH?and hydroquinone?HQ?are relatively simple and electrochemical actively,therefore,electrochemical methods can be applied to detect them.There exist inevitablely interactions of them?PAH and HQ?with solvents or other substances.Ionic liquids are a new type of excellent solvent,which have unique physicochemical properties and are widely applied in the fields of catalysis,extraction,separation,adsorption and electrochemistry.Ionic liquids have been usually used to fabricate various modified electrodes or electrochemical sensors to detect the PAH?HQ?content in wastewater.At the same time,ionic liquids can also be used as an alternative to traditional organic solvents for other studies of the two phenols,such as adsorption,extraction and separation,etc.The interactions between the ionic liquid and the above two phenols are the bases for theirs application,meanwhile,the performances of ionic liquids and phenols can be affect by the interactions.Therefore,studying the interactions between ionic liquids and PAH or HQ in aqueous solution can not only provide certain help for the phenols detection,extraction and adsorption in wastewater,but also improve the ionic liquids performances in other solutes extraction properties.In this paper,the interactions in three mixed systems?PAH-water,PAH-imidazole ionic liquid-water,HQ-imidazole ionic liquid-water?were investigated in detail.The specific details are as follows:1.The interactions of PAH and water were studied by UV-visible absorption spectroscopy,cyclic voltammetry?CV?,and nuclear magnetic resonance spectroscopy?NMR?.The results indicated that the formation of hydrogen bonds existed between-OH,-NH₃⁺in PAH and water molecules,which results in the electrochemical oxidation process of PAH changed more difficult and a hypsochromic shift in the UV-visible absorption spectra.The results of density functional theory?DFT?,atoms in molecules theory,and natural bond orbital analyses also indicated that hydrogen bonds existed in the system,which was consistent with the experimental results.In addition,the?-?stacking was also existed between PAH benzene rings from the NMR spectra at higher concentrations.2.The interactions of PAH and imidazole ionic liquids were investigated using NMR and CV.The experimental results indicated that the?-?stacking existed between PAH and ionic liquids,which enhanced the electrochemical activity of hydroxyl groups on the benzene ring in PAH,making it easier to oxidize.In addition,the interactions were also influenced by the structures of the cations and anions of the ionic liquids.3.Base on the interactions between HQ and water,the interactions of HQ and imidazole ionic liquid were studied by NMR and CV methords.According to the results of CV and NMR,it was found that when the ionic liquid were greater than the HQ concentrations,the mainly interactions were?-?stacking,on the contrary,hydrogen bond interactions were dominate.Quantum chemical calculations further confirmed the existence of hydrogen bonds and?-?stacking in the system.Furthermore,the structures of the anions and cations in ionic liquids also have different effects on the interactions.