Properties Of [C_npy]Br(n=3,5)Aqueous Solutions And Effects On The Physiology And Biochemistry Of Rape Seedings

Ionic liquids（ILs）refer to a kind of ionic compound whose cations are organic and are usually liquid at room temperature.ILs have many advantages,such as low vapor pressure,strong solubility,great chemical and thermal stability,adjustable properties,etc.ILs are gradually being widely used in the area of synthesis,electrochemistry,and environmental engineering as substitutes for traditional organic solvents.The application value of ILs is influenced by their properties.Therefore it is important to determine the properties of ILs.In addition,with the mass application of ILs,they will unavoidable flow into the environment.Due to their non-degradability,ILs have potential risks to the ecological environment.Assessing the environmental safety of ILs has attracted widespread attention.As a common intermediate in chemical synthesis,1-alkylpyridine bromide ionic liquids will inevitably enter the environment along with the discharge of industrial wastewater.Nowadays,ILs with pyridine have been required to carry out toxicological tests by the National Toxicology Program in the United States.Therefore,1-propyl bromide pyridine[C₃py]Br and 1-amyl pyridine bromide[C₅py]Br are selected as the research objects.Firstly,[C_npy]Br（n=3,5）were synthesized by the one-step way and characterized by ¹H NMR.Then mix[C_npy]Br（n=3,5）with water and determine their physical and chemical properties under different temperature conditions to provide data support for applying.Finally,the influence of[C_npy]Br（n=3,5）was studied on the physiological and biochemical indexes of rape seedling to explore their environmental toxicology.The specific contents and achievements of the research are as follows:[C_npy]Br（n=3,5）were synthesized by the one-step way.Pyridine and1-bromoalkane were as reactants and ethyl acetate as solvent to perform reflux reaction.After the process of suction filter and vacuum distillation,[C_npy]Br（n=3,5）were confirmed by ¹H NMR.The purity of[C_npy]Br（n=3,5）was above 99%.A binary mixture system of[C_npy]Br（n=3,5）with water in the range of0.050-1.000 mol/kg was prepared by gravimetric method.Density,viscosity,surface tension,electrical conductivity and refractive index of the solutions were measured at intervals of 5K at T=288.15K-318.15K and P=0.1MPa.The results showed that the density,viscosity,electrical conductivity and refractive index of the solution increased with the increase of molar concentration,while the surface tension showed an opposite trend.With the increase of temperature,the four properties of density,viscosity,surface tension and refractive index all decreased,while electrical conductivity increased.With the increase of the number of carbon atoms in the side chain,the density,surface tension,electrical conductivity and refractive index decreased gradually while the viscosity showed the opposite trend.Mix[C_npy]Br（n=3,5）and Hogland to prepare soluions with concentrations of10,50,100,200,300,400mg/L.Culture some rapeseeds with these solutions respectively.The indexes including the root length,plant height,activity of antioxidant enzyme,content of malondialdehyde and photosynthetic pigment were tested after eight days.The results show significant differences compared to the control groups.Low concentration of[C_npy]Br（n=3,5）at 10mg/L promoted the growth of rape seedlings.When the concentration was above 50mg/L,the solutions inhibitd the activity of antioxidant enzymes of rape seedlings and lead to the accumulation of MDA,causing ROS damage.At the same time,50mg/L[C_npy]Br（n=3,5）can inhibit photosynthetic pigment content and influence the process of photosynthesis,eventually hindering the growth of rape seedlings.Compared to the stems,the inhibitory effect of[C_npy]Br（n=3,5）was more significant than the roots.It was also found that the toxicity of[C₅py]Br was more than[C₃py]Br to rape seedlings.