Chlorine, aliphatic compounds

Liu Z, EA Betterton, RG Arnold (2000) Electrolytic reduction of low molecular weight chlorinated aliphatic compounds structural and thermodynamic effects on process kinetics. Environ Sci Technol 34 804-811. 

Although these issues have already been briefly noted, they deserve a few additional comments. For freely water-soluble substrates that have low volatility, there are few difficulties in carrying out the appropriate experiments described above. There is, however, increasing interest in xenobiotics such as polycyclic aromatic hydrocarbons (PAHs) and highly chlorinated compounds including, for example, PCBs, which have only low water solubility. In addition, attention has been focused on volatile chlorinated aliphatic compounds such as the chloroethenes, dichloromethane, and carbon tetrachloride. All of these substrates present experimental difficulties of greater or lesser severity. 

Eong JL, Stensel HD, Ferguson JF, et al. 1993. Anaerobic and aerobic treatment of chlorinated aliphatic compounds. J Environ Engin 119(2) 300-320. 

Kringstad, K.P. Ljungquist, P.O. de Sousa, F. Stromberg, L.M. Identification and mutagenic properties of some chlorinated aliphatic compounds in the spent liquor from Kraft pulp chlorination. Environ. Sci. Technol. 1981, 15, 562-566. 

Figure 91. Chlorinated aliphatic compounds originating from chemical synthesis.

Chlorinated aliphatic compounds are globally distributed. Natural product organohalides such as chloromethane and chloramphenicol are probably produced in diverse soil environments. Many halogenated organic compounds are biosynthesized by marine organisms (Neidleman Geigert, 1986), so the oceans area source as well. 

Figure 9.3. Elimination reactions of importance in the transformation of chlorinated aliphatic compounds. (A) gen-elimination (B) //-elimination.

Chlorinated aliphatic compounds are prevalent soil and groundwater contaminants and, thus, are increasingly becoming targets for bioremediation. Traditionally,... 

Research on biodegradation of chlorinated aliphatic compounds has been supported in my laboratory by research grants from the National Institutes of Health (GM 41235) and the Environmental Protection Agency (CR820771-01). 

Noryl is a rigid dimensionally stable material. Dimensional stability results from a combination of low mold shrinkage, low coefficient of thermal expansion (5.9 x 10-5 per° C), good creep resistance (0.6—0.8% in 300 h at 13.8 MPa (2000 psi)), and the lowest water absorption rate of any of the engineering thermoplastics (0.07% in 24 h at room temperature). Noryl resins are completely stable to hydrolysis. They are not affected by aqueous acids or bases and have good resistance to some oiganic solvents, but they are attacked by aromatic or chlorinated aliphatic compounds. 

PCBs > PAHs > chlorinated aliphatic alkanes > chlorinated aromatics > unsaturated chlorinated aliphatic compounds... 

Oxidation Model of Unsaturated Aliphatic Compounds The same transition complex approach and steady-state assumptions were used to develop the kinetic model of unsaturated chlorinated aliphatic compounds such as trichloroethylene (TCE). The model reflects the effects of H202, Fe2+, and organic compounds on the oxidation kinetics as follows ... 

The oxidation rates for bromoform were slower than the oxidation rates of unsaturated chlorinated aliphatic compounds, including the TCE. Because the hydroxylation rate constant of TCE is 109 Mr1 s 1 and the hydrogen abstraction of bromoform is 1.1 x 108 M 1 s aromatics and alkenes react more rapidly by hydroxyl addition to double bonds than does the more kinetically difficult hydrogen atom abstraction. No oxidative destruction of chloroform by Fenton s reagent was experimentally observed an explanation for this is that both H202 and Fe2+ have rate constants about one magnitude higher with respect to hydroxyl radicals than chloroform. 

ELUmo measures the ability of a molecule to accept electrons. Compounds with low Elumo tend to accept electrons easily. Thus, the coefficient of ELUMO is negative. Theoretically a compound with more negative AHf or lower AHf is more stable (Fried et al., 1977) therefore, it is reasonable that the coefficient of AHf in Equation (13.50) is positive, as shown in Table 13.13. Thus, the higher the AHf value is, the more unstable or reactive the chlorinated compounds will be. As a result, the log k values are greater. LFER analysis on dechlorination by Fe° of chlorinated aliphatic compounds, ELUMO, and AHf have been confirmed to be more significant molecular descriptors than other... 

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