Results

Degradation of compound 1, 2, or 3 at relatively high initial pH condition

As shown in Fig. 3-1 to 3-9, it shows the degradation of the compound 1, 2, and 3 both E and T isomer at an initial pH of 13.3, 128, or 11.9 with the final pH of 13.3, 12.5 and 11.5, respectively. The decreasing of the pH can mainly be attributed the formation of acidic reaction products. At pH 13.3, the stereo-preference was T over E isomer in the degradation of compound 1 and 3. By the way, the degradation of compound 2 showed no clear stereo-preference. In contrast, the stereo-preference of E over T isomer was observed in the degradation of any compound at an initial pH of 12.8 and 11.9 except the degradation of compound 3 at initial pH 11.9 which showed no stereo-preferential degradation. The results suggested that the degree of the stereo-preference was dependent on the structure of model compound employed. Moreover, the degree of the degradation of any compound became less with the decrease of the initial pH.

Degradation of compound 1 at relatively low initial pH condition

The stereo-preferential degradation of compound 1E or 1T was shown in Figure 3-10 to 3-13 with an initial pH of 11.5, 11.0, 10.5, or 9.5 and the final pH was 7.5, 6.0, 4.0, or 3.5, respectively. There was no clear stereo-preference observed between E and T isomers at any pH under these conditions.The degradation became clearly greater with the decrease of the initial pH.

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Degradation of compound 1 in Fenton’s reagent

The degradation of compound 1E or 1T under Fenton’s reagent is illustrated in Figure 3-14. Under the condition employed, the initial and final pH were 5.5 and 3.1, respectively. According to the observed result, there was no clear stereo-preference between E and T isomers, which is in accordance with the result in previous report. ^[6]

The amount of H2O2 used was 1/30 of that in the common reaction, because compound 1E or 1T already disappeared at a reaction time of 10 min after using the same amount of H2O2 as in the common reaction. This results can attributed to the difference in the H2O2

decomposition mechanism between Fenton’s and common reaction systems.Moreover, based on the results obtained, the generated HO and HO2 quite efficiently oxidized the compound rather than H2O2. Because the compound 1E was remained after the reaction using the same amount of H2O2 initially added at once (the ‘’ marks in Figure 3-14), it is at least certain that the oxidation power of H2O2 is efficiently utilized to oxidize the compound in the stepwisely reaction.

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FIGURE 3-1. Change in the yield of compound 1E or 1T when each compound was individually treated at the initial pH of 13.3. Each compound was run three times.

FIGURE 3-2. Change in the yield of compound 1E or 1T when each compound was individually treated at the initial pH of 12.8. Each compound was run three times.

60 70 80 90 100

0 10 20 30 40 50 60 70 80 90 100 110 120

Yield (mol%)

Reaction time (min)

1E 1T

60 70 80 90 100

0 10 20 30 40 50 60 70 80 90 100 110 120

Yield (mol%)

Reaction time (min)

1E 1T

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FIGURE 3-3. Change in the yield of compound 1E or 1T when each compound was individually treated at the initial pH of 11.9. Each compound was run three times.

FIGURE 3-4. Change in the yield of compound 2E or 2T when each compound was individually treated at the initial pH of 13.3. Each compound was run three times.

60 70 80 90 100

0 10 20 30 40 50 60 70 80 90 100 110 120

Yield (mol%)

Reaction time (min)

1E 1T

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0 10 20 30 40 50 60 70 80 90 100 110 120

Yield (mol%)

Reaction time (min)

2E 2T

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FIGURE 3-5. Change in the yield of compound 2E or 2T when each compound was individually treated at the initial pH of 12.8. Each compound was run three times.

FIGURE 3-6. Change in the yield of compound 2E or 2T when each compound was individually treated at the initial pH of 11.9. Each compound was run three times.

60 70 80 90 100

0 10 20 30 40 50 60 70 80 90 100 110 120

Yield (mol%)

Reaction time (min)

2E 2T

60 70 80 90 100

0 10 20 30 40 50 60 70 80 90 100 110 120

Yield (mol%)

Reaction time (min)

2E 2T

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FIGURE 3-7. Change in the yield of compound 3E or 3T when each compound was individually treated at the initial pH of 13.3. Each compound was run three times.

FIGURE 3-8. Change in the yield of compound 3E or 3T when each compound was individually treated at the initial pH of 12.8. Each compound was run only once.

60 70 80 90 100

0 10 20 30 40 50 60 70 80 90 100 110 120

Yield (mol%)

Reaction time (min)

3E 3T

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0 10 20 30 40 50 60 70 80 90 100 110 120

Yield (mol%)

Reaction time (min)

3E 3T

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Figure 3-9. Change in the yield of compound 3E or 3T when each compound was individually treated at the initial pH of 11.9. Each compound was run only once.

Figure 3-10. Change in the yield of compound 1E or 1T when each compound was individually treated at the initial pH of 11.5. Each compound was run three times. The

‘’ marks show the yield of compound 1E when treated with a low initial concentration of compound 1E (0.2 mmol/L). The reaction was run only once.

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0 10 20 30 40 50 60 70 80 90 100 110 120

Yield (mol%)

Reaction time (min)

3E 3T

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0 10 20 30 40 50 60 70 80 90 100 110 120

Yield (mol%)

Reaction time (min)

1E 1T

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Figure 3-11. Change in the yield of compound 1E or 1T when each compound was individually treated at the initial pH of 11.0. Each compound was run three times.

Figure 3-12. Change in the yield of compound 1E or 1T when each compound was individually treated at the initial pH of 10.5. Each compound was run three times.

0 20 40 60 80 100

0 10 20 30 40 50 60 70 80 90 100 110 120

Yield (mol%)

Reaction time (min)

1E 1T

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0 10 20 30 40 50 60 70 80 90 100 110 120

Yield (mol%)

Reaction time (min)

1E 1T

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Figure 3-13. Change in the yield of compound 1E or 1T when each compound was individually treated at the initial pH of 9.5. Each compound was run three times.

Figure 3-14. Change in the yield of compound 1E or 1T when each compound was individually treated in Fenton’s reagent. Each compound was run three times. The ‘’

marks show the yield of compound 1E when treated adding H2O2 initially all at once.

The reaction was run only once in this case.

0 20 40 60 80 100

0 10 20 30 40 50 60 70 80 90 100 110 120

Yield (mol%)

Reaction time (min)

1E 1T

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0 10 20 30 40 50 60 70 80 90 100 110 120

Yield (mol%)

Reaction time (min)

1E 1T

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TABLE 3-1: List of the initial pH, final pH, and stereo-preference observed in this study

Compound Initial pH Final pH Stereo-preference

1 13.3 13.3 T

12.8 12.5 E

11.9 11.5 E

11.5 7.5 no preference

11.0 6.0 no preference

10.5 4.0 no preference

9.5 3.5 no preference

5.5 3.1 no preference

2 13.3 13.3 no preference

12.8 12.5 E

11.9 11.5 E

3 13.3 13.3 T

12.8 12.5 E

11.9 11.5 no preference

*The grey line indicates Fenton’s reagent system

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