| Aromatic nitro compounds are important organic synthesis reagent.They have been widely used as chemical raw materials for medicine,spices,dyes,explosives and other industrial production.The investigation on the electron transfer mechanism can help us understanding the nature of aromatic nitro compounds and provide a reliable basis for biodegradation and synthesis of the compounds.In this thesis,the mechanism of electrochemical redox of p-nitrophenol?PNA?,p-nitrophenol?PNP?and 1,5-dinitro-naphthalene?DNN?in different solvents were explored by means of in situ FT-IR spectroelectrochemistry,cyclic voltabsorptometry?CVA?and derivative cyclic voltabsorptometry?DCVA?method.The main work is summarized as follows:1.The electrochemical behavior of p-nitroanisole?PNA?and p-nitrophenol?PNP?in acetonitrile?1?The cyclic voltammetry?CV?of p-nitroanisole?PNA?shows a pair of redox peaks.During CV scan,a series of IR absorption bands at 1272 cm-1,1341 cm-1,1518cm'1 tracing to PNA were observed simultaneously.In addition,IR absorption peaks(1156 cm-1,1241 cm-1,1487 cm-1 and 1595 cm-1)assigned to PNA·-were alsofound.Based on the results of CV and in situ FT-IR spectroelectrochemistry,we can conclude that the electron transfer mechanism of p-nitroanisole?PNA?in acetonitrile is a simple one-step electron transfer,i.e.,PNA + e???PNA ·-?2?The cyclic voltammetry?CV?of p-nitrophenol?PNP?shows complex redox peaks in the range of-0.3?-2.1?1 V.It was found that the two types of IR absorption bands at 1279 cm-1,1318 cm-1 which are related to intermediate.The absorbance value of 1279 cm-1 shows "increasing-increasing-decreasing-1 and other shows "increasing-decreasing-increasing" in the 3D spectra.The two types of IR absorption bands indicated that the PNP electrochemical process is accompanied by chemical reactions.First,PNP generates the anionic radical,and then protonation occurs.The energy of the two possible products was calculated by theoretical arithmetic,and the radical anion was found to be-OC6H4NOOH.It was found that the whole electrochemical process is chemically reversible by the consecutive scan.Based on the results of CV and in situ FT-IR spectroelectrochemistry,we can conclude that the protonated product reacts to produce dimer in the second step of the reduction process when the concentration of PNP is high.The structure of the dimer was confirmed by theoretical calculation.When the concentration of p-nitrophenol was decreased,the electron transfer mechanism will also change,that is,the dimerization phenomenon disappeared,and the anion free radical will continue to reduce.When the concentration of PNP is high,the possible reaction mechanism is as follow:HOC6H4NO2 + e???-OC6H4NOOH·HOC6H4NOOH·+-OC6H4NOOH· e???Dimer-OC6H4NO2+e???-OC6H4NO2·-Dimer?HOC6H4NOOH·-?-OC6H4NOOH'HOC6H4NOOH·--e?HOC6H4NOOH·When the concentration of PNP is low,the possible reaction mechanism is as follow:HOC6H4NO2 + e???-OC6H4NOOH·-OC6H4NOOH·+e???-OC6H4NOOH·--OC6H4NO2+e???-OC6H4NO2-2.The electrochemical behavior of 1,5-dinitronaphthalene?DNN?in acetonitrile and acetonitrile-proton donor mixed solvents?1?The cyclic voltammetry?CV?of 1,5-dinitronaphthalene?DNN?shows two pairs of redox peaks in acetonitrile.During CV scan,an IR absorption band at 1533 cm-1 tracing to DNN were observed simultaneously.IR absorption preaks(1018 cm-1,1143 cm-1,1249 cm-1)assigned to DNN·-were also found.In addition,the absorption peaks of DNN2-were observed at 1226 cm-1,1335 cm-1,1356 cm-1.Based on the results of CV and in situ FT-IR spectroelectrochemistry,we can learn that the electron transfer mechanism of 1,5-dinitronaphthalene?DNN?in protonated acetonitrile solution is a two-step single electron transfer,namely DNN + e???DNN·-,DNN ·-+e???DNN2-.?2?In the acetonitrile-ethanol mixed solvent,the cyclic voltammetry?CV?shows a pairs of redox peaks when the concentration of ethanol is low.In addition,it involves the formation of hydrogen bonding.The new redox peak is observed when the the concentration of ethanol is high,a little of DNN will form hydrogen bonds with ethanol,and then get an electron.When the concentration of ethanol is added to 20%,it can be seen from the 3D spectra that the absorption peaks of all the substances do not return to the base value,and the entire electrochemical behavior of the DNN becomes irreversible.When the concentration of ethanol is low,the possible reaction mechanism is as follow:DNN + e + mC2H5OH???DNN·-...· C2H5OHm DNN·-…C2H5OHm + e +?n-m?C2H5OH???DNN2-...?C2H5OH?nWhen the concentration of ethanol is high,the possible reaction mechanism is as follow:DNN...C2H5OHx + e???DNN-...2H5OHx DNN + e + mC2H5OH???DNN-·...C2H5OHm DNN-...C2H5OHm + e +?n-m?C2H5OH???DNN2-...?C2H5OH?n... |
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