Oscillatory reactions in the acetone-glucose-sodium bromate-sulfuric acid system with a tetraazamacrocyclic copper ( II ) complex as a catalyst

The behavior of glycolysis concerning the biochemical reaction was thought to be similar to the oscillatory reaction with glucose being the substrate. The objective of this research is to find a new oscillatory system and study its relevant properties, so new Cu (II)-catalyzed oscillating reaction involved glucose and acetone as the double substrates was investigated systematically. As a function of reaction temperature and concentration of glucose, bromate, and acetone, the features in this novel oscillation system was studied. The results showed that the activation energy reached up to 90.839 KJ/mol and the oxidized product of the double substrates provided the impetus in the course of the new oscillating reaction. A tentative mechanism was considered on the basis of FNK.


Introduction
Nature is the best teacher showing us how to effective use energy.Most creatures on the Earth, including animal, plant as well as yeast has shown an example of successful pathway taking energy from glycolysis [1].
Glycolysis that is the ultimate source of energy keeping creatures survive is the metabolic pathway that converts glucose into pyruvate and releases free energy to form the high-energy compounds ATP and NADH .It was first found that glycolysis is a determined sequence of ten enzyme-catalyzed complex reactions resulting in oscillation of NADH concentration in yeast in 1968 [2].
The Belousov-Zhabotinskii oscillating reaction was found long ago and studied thoroughly.The classical BZ oscillatory systems consist of malonic acid, Ce(IV)/Ce(III) or Mn(III)/Mn(II) redox catalyst and KBrO 3 in solutions of H 2 SO 4 [3].With regard to the catalyst in the BZ oscillatory systems, many researchers paid much attention to metallic ion in the past and further research on Ce(IV)/Ce(III) [4][5][6][7][8][9].In 1982, the tetraazamacrocyclic complexes of Cu(Ⅱ) and Ni(Ⅱ) were first found to act as a catalyst for BZ oscillating reactions.The design and synthesis of macrocycles and their metal complexes attract great attention, resulting from their widespread applications in biology, chemistry and in other applications of science [10].The features of the oscillating reactions catalyzed by tetraazamacrocyclic complex differ from the classical oscillating reaction in accordance with relevant literature [11][12][13][14].The tetraazamacrocyclic complex and organic substrate play a crucial role in the new oscillation reaction because the tetrazamacrocyclic complex is similar to some enzymes, so the newly oscillating reaction is deemed DOI: 10.1051/ 01005 (2016) to be a man-made biochemical scillation.It is significant to study the chemical oscillation on the basis of glucose as the analogy to glycolysis.

Result and discussions
As a result, this newly oscillatory system catalyzed by As shown from Fig. 1, the three conclusion can be made: Firstly,the oscillation can not exist without acetone in the whole oscillatory system.Secondly, when glucose is not added to the system,the oscillatory reaction still happen.Thirdly ,the double substrate can make the oscillatory amplitude bigger and the oscillatory period shorter than without glucose.
-  The reaction was also studied at different temperature , and the oscillation period (tp) was found to be inversely related to temperature.As the temperature increased, the oscillation period (tp) decreased.From the Arrhenius plot (Fig. 6) of l n (1/t p ) v s 1/T, the activation energy was calculated as 90.839 kJ/mol.
0.00325 0.00330 0.00335 0.00340 0.00345 0.00350 - LN(k) Fig. 6.The plot of ln(1/t p ) vs 1/T: The relationship between the potential of the platinum electrode and the potential of the bromide ion electrode is described iconically in the Fig. 7.In order to investigate whether free radical steps were involved, we tested H 2 O 2 [18][19][20].When the oscillations were held up briefly, the amplitude and oscillations decreased as soon as the concentration of H 2 O 2 in the oscillation system reached 9.7×10 -3 M.
This indicates that there are free radical steps involved in the mechanism of oscillation.
When the concentration of vitamin C in the oscillation system reached up to 1.0×10 -2 M, the chemical oscillations could be restrained momentarily, similar to the effect of vitamin C in the Ce(Ⅲ) catalyzing B-Z oscillation system [21][22] .This phenomenon makes it clear that HBrO 2 is a very important intermediate in the system.
By adding Ag + to the oscillation system, bromate ions concentration decreased due to the formation of AgBr precipitate, and the potentiometric oscillation of bromide selective electrode could be temporarily suppressed [23].From this, it can be seen that the concentration of Br -also acts as an on-off switch in the Therefore, the following reactions occur during the oscillation: Glucose is the energy source for human being.
The analogical research on the oscillatory reaction with glucose being substrate will help man to make clear the complex and significant biochemical mechanism.

Conclusion
New Cu(Ⅱ)-catalyzed oscillating reaction involved glucose and acetone as the double substrates is proved to be effective.This oscillation can not exist without acetone in the whole system but do without glucose.When the concentration of glucose increase to be 0.04M, the amplitude of oscillation is minimum, when the concentration of glucose increase to be 0.06, the amplitude of oscillation is maximum, but with the concentration of glucose increasing ,the period of oscillation reduce constantly.When it comes to the effect of the concentration of acetone , sodium bromate and tetraazamacrocyclic copper(Ⅱ) complex to the oscillatory parameters, there are the maximal of concentration respectively .the activation energy was calculated as 90.839 kJ/mol and this tentative mechanism is proved to be based on FNK through adding H 2 O 2, vitamin C and Ag + to the system respectively.

potentiometric oscillation traces of platinum electrode and bromide selective electrode are shown in Fig. 7 .
During the oscillations, the solution color changed periodically between orange and faint yellow, indicating the oscillation between [Cu L] 2+ and [Cu L] 3+ .At the same time ,the relationship between the potential of the platinum electrode and the potential of the bromide ion electrode is also studied in detail, through their potential respectively.

[Fig. 1 .
Fig.1.the effects of substrate on the oscillation

Fig. 2 .Fig. 3 .Fig. 4 .Fig. 5 .DOI
Fig.2.The effects of [Glucose] 0 on the oscillation period (tp),the amplitude of oscillation (A) at 30℃: [Acetone] 0 =0.65 M, [H 2 SO 4 ] 0 =1.05 M [CuL 2+ ] 0 =0.05 M ,[NaBrO 3 ] 0 =0.08 M As shown from the figure.2,oscillation still takes place without the glucose.The amplitude of oscillation decreased with increasing glucose concentration and reached a minimum at [glucose] 0 ca.0.04 M, then rose with further increasing the glucose concentration until the glucose concentration was 0.06 M, finally decreased as the glucose concentration increased.The oscillation period (tp) became increasingly shorter with increasing glucose concentration throughout the experiment.The effect of the concentration of acetone on oscillation parameter is shown in Fig.3.When the concentration of acetone was 0.85M, the oscillatory amplitude achieves the maximum.when the concentration of acetone increased to 1.05M,the oscillatory period is the longest.The effect of the concentration of CuL 2+ and NaBrO 3 oscillation parameter are shown in Fig.4 and Fig.5,respectively.Like the effect of acetone, the trend for the curve of the effect of CuL 2+ and NaBrO 3 on the oscillation