may or may not adequately attenuate the pesticide to an acceptable level.In the case of lindane, little effective attenuation through adsorption to the sand substrate would be expected from a continuous source. If the pesticide entered the aquifer in a slug, it might be adsorbed immediately and effectively removed from causing potential harm to the water interests. The leaching by uncontaminated waters may cause sufficient dilution to negate potential problems. However, the initially adsorbed lindane would be expected to be readily removed and transported, which could possibly cause harmful results to interests susceptible to chronic low-level exposure.An aquifer contaminated by dieldrin might be expected to react somewhat differently. The considerably increased capacity of the sand for dieldrin would result in an attenuation over a short distance. Once attenuated, the dieldrin might be expected to travel at a much slower rate and in lower concentrations than lindane. This difference would be expected to be magnified in areas where the groundwater contained appreciable amounts of dissolved organics.Variations of pH, particle size, and temperature likely to be found in most subsurface environments would have little effect on the disposition of either pesticide in the aquifer. Simple batch-type tests on the other chlorinated pesticides for comparison of uptake capacity can be expected to yield insight to permit an estimation of their relative disposition in a given aquifer.
The details of nitric oxide catalytic reduction by carbon monoxide and hydrogen over a supported ruthenium catalyst have been investigated. The feed stream used in these studies resembled automotive exhaust. The effect of space velocity and various reactant concentrations on the ammonia/nitrogen product distribution were studied along with the effect of these various parameters on the rate of nitric oxide removal. The pertinent chemical reactions in this system and the limitations imposed by an exhaust gas feed stream are discussed.
There are fundamental differences in the behavior of alumina-supported samples of a platinum and a copper-chromium catalyst for oxidation of carbon monoxide in a simulated automotive exhaust stream. Ignoring such differences can result in inappropriate comparisons between oxidation catalysts for automotive application.
Rates and isomer distributions in the elimination reactions of potassium r-butoxide in r-butyl alcohol at 50°with representative cycloalkyl and rrazis-2-methylcycloalkyl tosylates were determined in order to examine this reaction as a suitable probe for structural effects in E2 reactions and to test the relative advantages of the electronic and steric theories in accounting for the results. The rates of the simple cycloalkyl tosylates reveal only a modest change in the second-order rate constants with ring size (k2 X 104 mole-1 sec-1): cyclopentyl, 7.81; cyclohexyl, 2.14; cycloheptyl, 2.34; cyclooctyl, 1.28. rra«i-2-Methylcycloalkanols were synthesized via the hydroboration of the 1 -methylcycloalkenes and the tosylates were subjected to elimination. The 99% 3-, 1 % 1-distribution in the first three members reveals stereoelectronic control requiring the usual trans coplanar arrangement of the atoms involved in the elimination stage. However, a 50-50 formation of the two olefins was observed in the cyclooctyl derivative, presumably a result of the greater flexibility of the eight-membered ring. Finally, the rates of elimination of rra/w-2-methylcyclopentyl (1.10) and -cycloheptyl tosylate (0.84) are only moderately slower than those of the parent compound, but the rate constant for the corresponding cyclohexyl compound, 0.024, is markedly depressed from the rate constant for the parent structure, 2.14. The slow rate in cyclohexyl system can be attributed to the energy required to place both the methyl and the tosyl groups in the axial position.
The reaction of the 2-butyl and /-amyl halides with potassium /-butoxide in /-butyl alcohol has been examined in order to establish the direction of elimination as a function of the halogen. The ratio of 1-olefin to 2olefin increases in the order, chloride > bromide > iodide, in both series. The axial-equatorial equilibria of cyclohexyl compounds is proposed as a model for the steric interactions in the transition state for the E2 reaction. On this basis, the steric requirements of the halide leaving groups increase from iodide to bromide to chloride. These results in the halide series are consistent, therefore, with the previously suggested role of steric effects in shifting the direction of elimination from Saytzeff to Hofmann. It is pointed out that solvation, both of the attacking base and of the leaving group, must be considered in estimating their steric requirements and influence on the direction of elimination.
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