| For the last few decades,the field of non-linear chemical dynamics has significantly grown in breadth and depth.Oscillating chemical reaction is one of the best kind of non-linear chemical dynamics,which has been widely and thoroughly investigated.The parameters of oscillating chemical reactions includes,changes in the period of oscillations?AT?,changes in the oscillation amplitudes??A?,inhibition time?tin?,variation in the duration of oscillations?N?.All of these parameters were directly related to the concentrations of additives?reactants,products or intermediate species?with respect to time.The mechanism of oscillating chemical reaction is often very complex,consisting various intermediates species and kinetic determination steps.The achievement of famous mechanisms?FKN and FCA?for oscillating reactions?Belousov-Zhabotinsky and Briggs Rauscher?respectively by the few years struggle of great well-known scientists?Field,Koros,Noyes?made the oscillating reactions much expressly to researchers and readers.However,my "Thesis" is based on"Research based on the analytical applications of a novel Briggs Rauscher?BR?and a Belousov-Zhabotinsky?BZ?chemical oscillator.This "Thesis" is classified into 7 chapters.The first chapter is based on introduction while 2-7 chapters are my experimental work.The introductory section is based on the detail overview of literature i.e.the study of non-linear chemical dynamics and its detail classifications?chemical oscillation,chaos,waves,and patterns?.The historical background and progress in the oscillating reactions in both research and mechanism have been discussed.In the 2nd chapter,a study on the determination of an antioxidant ethyl vanillin?EV?built on its perturbation effects on a Briggs-Rauscher?BR?oscillator was reported.A tetraazamacrocyclic Ni???complex,[NiL]?ClO4?2,was used as a catalyst in such a oscillator,and the ligand L in the complex is 5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene.The pH value for the BR reaction was kept at 2,which is analogous to the pH of the fluids of the human stomach.It has been concluded from the experimental data that the addition of EV into BR system could cause the temporary cease in the oscillation after inhibition time?tin?depending on the concentration of EV added.It was found that,as the concentration of EV were increased,the tin were increased.Thus,a polynomial regression curve was achieved over a range 7.50×10-6 to 3.50×10-5mol/L of EV with a correlation coefficient of 0.98.The obtained RSD from six measurements of 2.50×10-5 mol/L of EV is 0.159%.On the basis of the FCA model,the reaction mechanism involving HOO· radical has been proposed.A suitable and convenient method for the analytical determination of morin was established by using Briggs-Rauscher chemical matrix?BR?in the 3nd chapter.The macrocyclic Ni-complex[NiL]?ClO4?2 was used as catalyst.The ligand L in the complex is 5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene.Experimental data has absolutely indicated the inhibitory effect caused by morin on the active BR system.Different concentrations of morin ranging 2.44×10-6 mol/L to 1.30×10-5 mol/L have been tested.As a result,oscillating system stopped to oscillate for some instant and then successfully regenerated.Such phenomenon has concentration dependent,meaning as the concentration of morin were increased,the inhibition time?tin?of the system were increased and vice versa.Thus,by plotting tin against concentrations of morin,a linear regression curve was obtained over a concentration range from 2.44×10-6 mol/L to 1.30×10-5mol/L of morin with correlation coefficient of 0.98.The calcuated RSD value is 2.56%,which was obtained by the 5-measurements of 1.30×10-5 mol/L morin.Although the reaction of morin and KIO3 was confirm through cyclic voltammetry experiment,actually the tin was caused due to the reaction of morin with HOO· radical?produced during oscillatory reaction?.Briggs-Rauscher?BR?reaction is one of the best thoroughly investigated chemical oscillator,and it has been utilized for the determination of p-coumaric acid?antioxidant?in 4th chapter.The macrocyclic Ni complex[NiL]?ClO4?2 was used as catalyst in the BR oscillator where ligand L in the complex is 5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene.Experimental results have shown that,the addition of p-coumaric acid into the active BR oscillator could cause the temporary cease in the oscillation?inhibition time?.Such temporary termination of the system has directly proportional to the concentration of p-coumaric acid added.As the concentration of p-coumaric acid were increased the tin of the system were increased.Thus linear regression curve over a concentration range from 6.50 x 10-5 to 2.25×10-4 mol/L of p-coumaric acid Vs tin with a correlation coefficient 0.99 was achieved.The observed limit of detection?LOD?is 1.50 x 10-5 mol/L.The RSD calculated from 6 measurements of 1.0 x 10-4 mol/L of p-coumaric acid is 2.24%.The perturbation mechanism involving hydroperoxyl radical?HOO·?on the basis of FCA mechanism has been proposed.A suitable method by means of Briggs-Rauscher?BR?oscillating system as an analytical technique to identify the two positional isomers between ortho-vanillin?OV?and?para-?vanillin?PV?by their different perturbation effects has been proposed in 5th chapter.In BR system the macrocyclic Ni-complex,[NiL]?ClO4?2 was used as catalyst,in which ligand L is 5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene.The experimental data has proven that putting equal amount of same concentrations of these isomers?OV and PV?separately into the active BR system could cause the inhibition time?tin?.But the tiin initiated by OV is higher as compared to the tin produced by PV.Our predication for such.different inhibitory effects caused by these isomers may be due to their different existing strength of intermolecular hydrogen-bonding.Furthermore,by plotting tin against the concentration of OV or PV,two linear regression curves were achieved for these two isomers in their concentrations range 2.50 x 10-6 mol L-1 to 4.0 x 10-5 mol L-1 with correlation coefficients of 0.98,which obviously illustrated the different behaviors of isomers.The perturbation reaction mechanism,involving hydroperoxyl radical?HOO·?on the basis of FCA has been proposed.The description of the proposed mechanism is that these isomers react with hydroperoxyl radical to form a dimeric product?divanillin?.The Belousov-Zhabotinsky oscillator?BZ?is one of the thoroughly investigated chemical oscillator which was used for the identification of two functional group isomers?propanal and acetone?in the 6th chapter.The Cu-complex[CuL]?ClO4?2 was used as catalyst,where L in the complex is 5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene.Experimental analysis indicated the quite different behaviors of propanal and acetone toward BZ oscillator.The same amount of the same concentrations ranging(1.0×10-4 mol/L to 1.90×10-3 mol/L)of both isomers were used separately to perturb the active BZ system.It was found that,the perturbation effect of propanal could cause the decrease in the amplitude of oscillation whereas no influence has been observed by the addition of acetone into the active BZ system.It was further examined that,the increase concentrations of propanal within the system remarkably increases the change in the amplitude of oscillation?AA?while the increase amount of acetone has no effect over system.On the basis of FKN mechanism,the reaction perturbation mechanism has been proposed.A new method for identification of three isomers of mono hydroxy benzoic acid?HBA?was reported by using their different perturbation effects on two chemical oscillators:a Briggs-Rauscher?BR?oscillator and a Belousov-Zhabotinskii?BZ?oscillator.To the BR system,the 2-hydroxybenzoic acid?2-HBA?caused a decrease in potential?amplitudes?,an increase in period of oscillation??T?and a decrease in number of oscillation cycle?n?while no influences of 3-hydroxybenzoic acid?3-HBA?and 4-hydroxybenzoic acid?4-HBA?on the oscillations were observed.For the BZ system,the 3-HBA could temporarily quench and regenerate oscillations after inhibition time?tin?while 4-HBA could only change the amplitude of oscillation?AA?with no inhibition time.Thus,these three isomers of HBA were identified.Reaction mechanisms of BR and BZ have been proposed by FCA and FKN models,respectively.An explanation of perturbation mechanism on BR is that,only 2-HBA reacted with IO3-to form 1,2-quinone while the 3-HBA and 4-HBA didn't.The perturbation mechanism on BZ is that,although 3-HBA reacted with BrO2· while 4-HBA reacted with BrO3-,they all produced 1,4-quinone. |
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