Chlorinated phenols structures

PCDFs are similar in many respects to PCDDs but have been less well studied, and will be mentioned only briefly here. Their chemical structure is shown in Figure 7.1. Like PCDDs, they can be formed by the interaction of chlorophenols, and are found in commercial preparations of chlorinated phenols and in products derived from phenols (e.g., 2,4,5-T and related phenoxyalkanoic herbicides). They are also present in commercial polychlorinated biphenyl (PCB) mixtures, and can be formed... 

Fig. 10.7 Structural formulae of phenolic disinfectants A, clear soluble fluids B, black and white fluids C, chlorinated phenols D, bisphenols.

Most acid dissociation constants pKa exceed environmental pH values, the exceptions being the highly chlorinated phenols. As a result, these substances tend to have higher apparent solubilities in water because of dissociation. The structure-property relationships apply to the un-ionized or protonated species thus, experimental data should preferably be corrected to eliminate the effect of ionization, thus eliminating pH effects. 

Numerous studies on the metabolism of 2,1t-dichlorophenoxy-acetic acid (2,1+-D) and related herbicides in animals have shown that these chemicals are absorbed and distributed rapidly in the body, and are excreted, undegraded, relatively quantitatively in the urine within a week after administration (M Pharmacokinetic studies with 2,1+,5-T in rats and dogs (5.) and in humans (6J supported these findings, and demonstrated that rates of clearance from plasma and elimination in urine depend on dosage level, animal species, and chemical structure of the phenoxy acid being studied ( + ). Corresponding chlorinated phenol metabolites were detected only in ruminants (M or in trace amounts in urine of rats fed very high doses of phenoxy herbicides (7.) ... 

Although the free phenolic structures are oxidized faster, chlorine dioxide also destroys nonphenolic phenyl propane units and double bonds present in the pulp chromophores. After cleavage of the benzene ring various di-carboxylic acids are formed, such as oxalic, muconic, maleic, and fumaric acids in addition to products substituted with chlorine (Fig. 8-10). As a result of depolymerization and formation of carboxyl groups the modified lignin is dissolved during the chlorine dioxide treatment and in the sodium hydroxide extraction stage that usually follows. 

Methods for the removal of low concentrations of species from effluent which involve either oxidation or adsorption will clearly require a cheap but high-surface-area electrode structure, and several carbon bed and carbon fibre electrode cells have been described. The latter are prepared from 5—15 fxm diameter carbon fibre which has a specific area of 260 m g and hence permits a high throughput of effluent. Such a cell has been used for treatment of paper mill effluent and a 70% reduction of BOD with a 95% removal of highly toxic chlorinated phenols has been claimed. 

Acute toxicity in fish, bioconcentration in fish, chlorinated hydrocarbons, chlorinated phenols, molecular connectivity indices, molecular topology, nonempirical quantitative modelling of environmental properties, polycyclic aromatic hydrocarbons, quantitative structure activity correlations, soil sorption, Pimephales promelas, fathead minnow, connectivity indices, sheepshead minnows, Cyprinodon variegatus. 

Using thiophenol instead of phenol, Michel et al. [49] found a new selective reaction that takes place exclusively with allylic chlorines and not with tertiary chlorines. A single product of thioether structure is formed [Eq. (11)]. 

Millan and coworkers (99-101) also studied the effect of tacticity on the nucleophilic substitution reactions of PVC. Sodium thiophenate and phenol were used for these reactions. The central chlorine in isotactic triads and, to a lesser extent, in heterotactic triads was found to be most reactive. It was concluded that initiation of degradation may occur by normal structures, and polyene build-up may be favored by syndiotic sequence. This... 

Bakke et al. (1982) have shown how montmorillonite catalyses chlorination and nitration of toluene nitration leads to 56 % para and 41 % ortho derivative compared to approximately 40 % para and 60 % ortho derivatives in the absence of the catalyst. Montmorillonite clays have an acidity comparable to nitric acid / sulphuric acid mixtures and the use of iron-exchanged material (Clayfen) gives a remarkable improvement in the para, ortho ratio in the nitration of phenols. The nitration of estrones, which is relevant in making various estrogenic drugs, can be improved in a remarkable way by using molecular engineered layer structures (MELS), while a reduction in the cost by a factor of six has been indicated. With a Clayfen type catalyst, it seems possible to manipulate the para, ortho ratio drastically for a variety of substrates and this should be useful in the manufacture of fine chemicals. In principle, such catalysts may approach biomimetic chemistry our ability to predict selectivity is very limited. 

We have recently evaluated the chlorendic imide/hindered phenol for its effect on the oxygen index of polyethylene, and we found only a miniscule increase, not considred statistically significant, in comparison to the same loading of chlorine as chlorendic anhydride. We believe that if the antioxidant approach to flame retardancy is to be successful, special high temperature antioxidant structures must be designed for this purpose. 

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