Secondary formation

After completion of this diffusional process within a few /us, in other words after the consumption of S04 and formation of Py + or G+, interestingly, a larger amount of Py+ was formed for PyODNn with a shorter distance separation between the G-region and Py moiety in the time scale of 100 /is (Fig. 3a). This secondary formation of Py + was attributed to the hole transfer from G + to Py in DNA (Scheme 3, path b). Since the hole transfer from the G-region to the Py moiety is considered to be much slower for Py-ODN5 compared to the PyODNn (n=l 4), in the case of PyODN5 Py + was formed only from the initial collision process the time profile of Py+ at 470 nm for PyODN5 was subtracted from those for PyODNn (n=l 4). This... 

The pulse radiolysis of ODN conjugated with Py and Ptz showed a transient absorption spectrum with a peak at 470 or 520 nm, assigned to Py+ or Ptz + respectively (Fig. 9). The formation rates of Py+ and Ptz+ obtained for Py-1 and Ptz-1 were almost identical to that of the decay of TIOH+ and no secondary formation was observed. These results indicate that a hole migrates from... 

On the other hand, when the distance between Py and Ptz was longer (PtzPy-3) with five A-T base pairs, the formation and decay of Py + were observed in the time range of 0-100 /zs after an electron pulse. At 100 /US only Ptz + was observed (Fig. 10b). This result indicates that a hole migrates from Py + to Ptz within 100 fis. >From the time profiles of absorption peaks at 470 nm for Py + and 520 nm for Ptz +, secondary formation of Ptz + was also observed concomitant with the decay of Py + for PtzPy-3, while no secondary formation of Ptz + was observed for PtzPy-1 due to the rapid hole transfer (Fig. 10c,d). The rate constant of the hole transfer from Py + to Ptz was determined to be 2.0X104 s 1 for PtzPy-3 from the decay of Py +. 

As mentioned in the introduction, there are conflicting views as to the contributions made to polymer degradation by various initiating species. Among these species, in addition to ketones, hydroperoxides are some of the more important chromophores. As it is known, the photolysis of hydroperoxides yields alkoxy and hydroxy radicals. In polymers, in the presence of oxygen, these radicals lead to the secondary formation of peroxy radicals. The latter in turn are converted by hydrogen abstraction into new hydroperoxides (Scheme I) ... 

Figure 9. This model shows three left-handed helical submicrofibrils (SM) 1, 2 and 3 which emerged from the cell wall at their termini. It was not clear how the submicrofibrils first associated with other submicrofibrils but once associated they were spun together. This model assumed that cellulose synthesis provided the mechanical force that simultaneously extended and left-hand rotated the submicrofibrils, which in turn drove the secondary formation of three submicrofibrils into a left-hand helical microfibril (M).

Blando, J. D., R. J. Porcja, T.-H. Li, D. Bowman, P. J. Lioy, and B. J. Turpin, Secondary Formation and the Smoky Mountain Organic Aerosol An Examination of Aerosol Polarity and Functional Group Composition during SEAVS, Environ. Sci. Technol., 32, 604-613 (1998). 

Refluxing a mixture of (lS, 4S, 7RS, 8R, 9R )-7-hydroxy-8-isobutyl-9-methyl-6-azatricy-clo[6.1.1.04-9]decane-6-carbaldehyde (5) and 95% formic acid for 12 hours gave a 1 1 mixture of (E)- and (Z)-(l/ , 4S,, 7S, 8/ )-9-isobutylidene-8-methyl-2-azatricyclo[5.2.1.04-8]decaiie-2-carbaldehyde (6) and the secondary formate (lR, 4S, 77 , 8R, 10S )-10-isobutyl-8-formy-loxy-7-methyl-2-azatricyclo[5.2.1.04,1°]decane-2-carbaldehyde (7) in 24% and 55% yield, respectively.87 The rearrangement is believed to involve the cyclobutyliminium ion, as shown.87... 

There would appear to be no difference in the reactions expected photo-chemically as the primary products are H atoms and OH radicals in both the electric discharge and on irradiation. Chen and Taylor (22) state that there is no evidence for oxygen atoms either in the photolysis or in the decomposition of water vapor in an electric discharge. However, the secondary formation of O atoms (2) and the formation of ozone (31, 50) in an electric discharge through water vapor have been demonstrated. It might be expected that under the proper experimental conditions similar results could be obtained photochemically. 

Schcllmann, W., 1966. Secondary formation of chamosite from goethite. Z. Erzbergbau Metall-huttenw., 19(6) 302-305. 

The disadvantages of the chemical technique of tetraethyllead production are the low degree of reactant transformation (75% of the lead does not enter the reaction) and secondary formation of sodium chloride. Besides, it is very problematic to extract tetraethyllead out of the spongelike mass, the mixture of lead and sodium alloy and sodium chloride completely. The process is periodic and hence difficult to automate. Electrochemical techniques for the synthesis of tetraethyllead seem to be more promising in this aspect. 

At room temperature trichlorfon is stable however, in the process of production and purification it is exposed to high temperature for a length of time, which reduces the yield of trichlorfon due to the secondary formation of 0,0-dimethyl-0-(2,2-dichlorovinyl)phosphate ... 

Thus an essential condition for such reactions is the secondary formation of a multiple bond, which is not necessarily a terminal process. 

Balzer W, Pluschke P (1994), Chemosphere 29 1889-1902.. .Secondary formation of PCDD/F during the thermal stabilization of sewage sludge"... 

In the case of photooxidation of heptanal (R = w-CeHis) in the liquid phase, a recent study using infrared spectrophotometry - also establishes the secondary formation of a peroxide X and assigns to it formula (B). 

Niclause, Combe, and Letort - also demonstrated, between 1952 and 1955, that, in the slow thermal oxidation of gaseous ethanal and propanal at about 100-150°C., a process of degenerated chain branching appears during the course of the reaction, that is caused by the secondary formation of free radicals from the peracid, a feature which explains the aqto-... 

As an example of this type of work. Fig. 1.13 indicates the care with which the initial values of [(CHsCOCHg) + (DMO)]/t/[/-C4H8] were obtained for a range of the mixtures used at 753 K. Typically the ratio was determined over the first 5-10% consumption. As can be seen, the change in the ratio is significant and arises from a complex mechanism often involving secondary formation of products and widely differing rates of removal of the intermediate products. Here, for example, acetone is... 

As shown in Fig. 1.15, benzene is formed as a secondary (probably tertiary) product when cyclohexane is added to H2 + O2 mixtures at 753 K. Use of cyclohexene [93] as additive shows secondary formation of benzene, and when cyclohexadiene is the additive, benzene is formed as a primary product in yields of 60-70%. Clearly then cyclohexane and substituted cyclohexanes will be major sources of aromatics in the temperature region 600-1000 K. The formation is eased by the production of delocalized cyclohexenyl and cyclohexadienyl radicals which hastens the sequence through to benzene as shown below where X = OH, HO2 usually. 

Isotope-labeling experiments and the secondary formation of regioisomers show that the Pictet-Spengler condensation may be reversible under more vigorous conditions. ... 

Turpin B. J. and Huntzicker J. J. Secondary formation of organic aerosol in the Los-angles basin - a descriptive analysis of organic and elemental carbon concentrations. Atmos. Environ. 1991, Vol 25A, No. 2, 207-215. 

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