Chlorophenol experimental results

Ferrihydrite catalysis of hydroxyl radical formation from peroxide has also shown experimental results consistent with a surface reaction [57]. The yield of hydroxyl radical formation was lower for ferrihydrite than for dissolved iron, resulting in a higher peroxide demand to degrade a given amount of pollutant. As mentioned above, although ferrihydrite exhibited a faster rate of peroxide decomposition than goethite or hematite, the rate of 2-chlorophenol degradation with these catalysts was fastest for hematite [55], In other studies, quinoline oxidation by peroxide was not observed when ferrihydrite was used as catalyst [53]. 

However, GC-MS and HPLC analysis indicate that the only detectable trihydroxybenzene is hydroxyhydroquinone, and no CTHB is detected. This result may indicate either that CTHB is not stable (it quickly degenerates to other species after it is formed) or that this pathway is not favorable. 4-Chlo-rocatechol has fewer hydrogen atom sites than 4-chlorophenol. Therefore, the chance of OH radical attack on the hydrogen atom site of 4-chlorocatechol will be smaller than the chance of a similar attack on the hydrogen atom sites of 4-chlorophenol. Conversely, there are more chances for OH radical attack on the chlorine atom site. The experimental results suggest that the dechlorination reaction is the main pathway to formation of hydroxyhydroquinone, although the formation of chlorotrihydroxybenzene still cannot be excluded. 

Fuchs and Tiganik have devised a formula by which the total moment of a molecule can be calculated if it possesses two separate moments, fn and which are able to rotate freely round certain axes fixed in space. In substituted benzenes, it is possible, by comparing experimental results with the requirements of this formula, to decide whether the rotary power of the polar groups is free or impeded. In m- and p-derivatives, e.g. in the chlorophenols, bromophenols, nitrophenols, etc., essentially unimpeded rotatory power of the OH-dipole round the C—0 bond occurs, while in the o-derivatives, the mutual interaction of the substituents is so considerable that mobility is greatly impeded. There is experimental evidence... 

The last few years have seen the emergence of projects aiming at elucidating the photobehavior of monochlorophenols in heterogeneous systems. Two studies were concerned with the behavior of 4-chlorophenol in a surface-adsorbed state, the substrates being silicalite and solid /Tcyclodextrin [40], and cellulose and silica [41]. In both cases, nanosecond transient photolysis with diffuse reflectance detection and photoproduct analysis were the experimental techniques employed. The results of these investigations are instructive in demonstrating the influence of the solid support on the outcome of the photolytic reactions. 

Equations (7-9), (7-10) and (7-11) allow modeling the photo-catalytic conversion of 2-chlorophenol and 2,4 dichlorophenol, under this special case and, as a result, without the requirement of having to define q . Only the groups k cuhq. m and K q are assessed with experimental data. 

Most studies in TLC have been qualitative, and considerable experimentation may be necessary to obtain quantitative results, although excellent commercial layers and new equipment have aided the problem. Phenolic compounds have been analyzed by spectrophotometry off the plate at 725 nm (133) by means of Folin-Ciocalteu reagent, essentially sodium tungstate and molybdate with lithium sulfate (134). Chlorophenols have been quantified after reaction with dansyl chloride and separation (135). Channel TLC (linear relationships between spot lengths and concentration between 1 and 8 pg/spot) has been used (136). The phenols in cashew nut shell liquid have been quantified by off and on the plate methods with a flying-spot scanning procedure and densitometry (137) and the distribution of unsaturateds by TLC/MS (138). Catecholamines and their metabolites in urine have been quantified (12) and determined by on the plate fluorimetry (139). Hindered phenols have been analyzed by densitometry (140). Semiquantitative determinations of the coupling products of 4,4 -... 

A typical example is shown in Fig. 20.11. Both theoretical and experimental COD and ICE trends are given for the anodic oxidation of 4-chlorophenol at a BDD anode. As can be seen, the model is in good agreement with the experimental data. Similar results were obtained for almost all of the organic compounds investigated (Table 20.1). 

---