Ozone additivity towards

Ozonation of benzo[r,s,t]pentaphene (7) followed by oxidative workup led to benzo[r,s,t]pentaphene-5,8-dione (12) (14%), phthalic acid (13) (4%), p-terphenyl-2,2, 3, 2"-tetra-carboxylic acid-2, 3 -anhydride (14) (10%), and 2-(o-car-boxyphenyl)- ,10-phenanthrenedicarboxylic acid anhydride (15) (3%), with a 56% recovery of unreacted 7, Ozonation of pentaphene (11) led to a peroxidic mixture which on oxidative workup led to 2,2 -binaphthyl-3,3 -dicarboxalde-hyde (16) (16%), 2,2 -binaphthyl-3,3 -dicarboxylic acid (17) (16%), and 13 (2%), with a 28% recovery of unreacted 11. A comparison of the reactivity to ozone of carcinogenic polycyclic aromatics benzo c]phenanthrene (1), 7,12-di-methylbenz [a] anthracene (2), 3-methylcholanthrene (3), dibenz[si,]] - (4), and dibenzlsi, ]anthracene (5), benzo Si -pyrene (6) and 7, and the noncarcinogen 11, all determined in our laboratory, leads us to conclude that there is no simple, consistent correlation between carcinogenicity, K-and L-region additivity towards ozone and the Pullmans electronic theory of carcinogenesis. 

Chemical/Physical. The gas-phase reaction of ozone with pyridine in synthetic air at 23 °C yielded a nitrated salt having the formula [CeHsNHJ NOs (Atkinson et al., 1987). Ozonation of pyridine in aqueous solutions at 25 °C was studied with and without the addition of ferf-butyl alcohol (20 mM) as a radical scavenger. With tert-hniyX alcohol, ozonation of pyridine yielded mainly pyridine W-oxide (80% yield), which was very stable towards ozone. Without terf-butyl alcohol, the heterocyclic ring is rapidly cleaved forming ammonia, nitrate, and the amidic compound W-formyl oxamic acid (Andreozzi et al., 1991). 

In addition to ozone depletion, the greenhouse effect is important. Greenhouse warming potential (GWP) of a compound depends primarily on its reactivity towards hydroxyl free radicals, which in turn determines their concentration in the stratosphere. A second factor is their absorption capacity for infra-red radiation, primarily determined by bonds between carbon and... 

In contrast with the behaviour of typical vinylphosphonic acid derivatives, the carbon-carbon double bond in the 1,2-oxa-phospholene (167) is remarkably unreactive towards a broad spectrum of reagents including electrophiles, most epoxidizing and organometallic reagents, as well as to dipolar addition reactants. Exceptional reagents are, however, N-bromoacetamide (NBA), ozone, dimethyllithiumcuprate, and sodium-naphthalene. 

Analogous approaches to assessing VOC reactivities have been developed by Derwent and co-workers (e.g., see Hough and Derwent, 1987 Derwent and Jenkin, 1991 and Derwent et al., 1996) where a trajectory model is used to calculate the additional ozone production due to the addition of a particular VOC under conditions typical of air masses advected across northwest Europe toward the British Isles. The photochemical ozone creation potential (POCP) index thus calculated is a measure of the reactivity of the particular VOC in terms of 03 formation. Andersson-Skold and co-workers (1992) followed a similar approach for the summer conditions in southern Sweden. 

If compounds already react very fast with ozone, the addition of hydrogen peroxide is nearly ineffective, which was shown by Brunet et al. (1984) in the case of benzaldehyde and phthalic acid. The functional groups on the aromatic ring are relatively reactive towards molecular ozone. The advantage of this process lies in the removal of compounds relatively non-reactive with ozone. It was shown that the oxidation of oxalic acid, which is often an end product in the case of molecular ozone reactions, was significantly accelerated with the addition of hydrogen peroxide. 

In addition to OH radicals, unsaturated bonds are reactive towards O3 and NO3 radicals and reaction with these species is an important atmospheric degradation mechanism for unsaturated compounds. Table 4 lists rate constants for the reactions of 03 and NO3 radicals with selected alkenes and acetylene. To place such rate constants into perspective we need to consider the typical ambient atmospheric concentrations of O3 and NO3 radicals. Typical ozone concentrations in pristine environments are 20-40 ppb while concentrations in the range 100-200 ppb are experienced in polluted air. The ambient concentration of NO3 is limited by the availability of NO sources. In remote marine environments the NO levels are extremely low (a few ppt) and NO3 radicals do not play an important role in atmospheric chemistry. In continental and urban areas the NO levels are much higher (up to several hundred ppb in polluted urban areas) and NO3 radicals can build up to 5-100 ppt at night (N03 radicals are photolyzed rapidly and are not present in appreciable amounts during the day). For the purposes of the present discussion we have calculated the atmospheric lifetimes of selected unsaturated compounds in Table 4 in the presence of 100 ppb (2.5 x 1012 cm 3) of O3 and 10 ppt (2.5 x 108 cnr3) of NO3. Lifetimes in other environments can be evaluated by appropriate scaling of the data in Table 4. As seen from Table 4, the more reactive unsaturated compounds have lifetimes with respect to reaction with O3 and NO3 radicals of only a few minutes ... 

The results of the early work led to a second phase directed toward NO2 absorption by aqueous solutions, notably sulfites. This effort presumed the prior oxidation of NO to NO2 by a suitable technique such as ozone addition or catalysis. In these latter scrubbing studies, SO2 was usually present in the flue gas and was found to be beneficial for NO2 absorption. The results from the second phase are quite promising and indicate the technical possibility of simultaneous NO2/SO2 scrubbing. 

Toward the end of the water treatement process to minimize THM formation and provide secondary disinfection Prior to the rapid mixing step in all treatment processes, except GAC and conventional treatment processes prior to fdtration for GAC post-sedimentation for conventional treatment. In addition, sufficient time for biodegradation of the oxidation products of the ozonation of organic compounds is recommended prior to secondary disinfection. Toward the end of the water treatment process to minimize presence of other contaminants that interfere with this disinfectant. 

Fortunately, a number of simplifications are possible. First, it may be noted that the O-atom concentration approaches the steady state much faster than the ozone concentration. At 50 km altitude, the time constant for the adjustment to steady state of n, is r0= l/fcbn2nM = 20s, and the value decreases as one goes toward lower altitudes. The time constant for the approach to steady state of ozone, in contrast, is much longer, and it increases with decreasing altitude (see below). It is thus reasonable to assume that oxygen atoms are always in steady state, that is, dn,/dt = 0. In addition, it turns out that the second and third terms in Eq. (3-1) are dominant compared with the other two. Accordingly, one has approximately... 

Nitrous oxide is produced as a byproduct in multimillion Ib/year quantities in nylon manufacture worldwide. Currently, there is a great interest toward the utilization of NjO due to the environmentally hazardous nature of this gas with respect to the greenhouse effect and ozone layer depletion. In addition to their ability to utilize dioxygen for catalytic hydrocarbon oxidations, ruthenium porphyrins have been shown to activate nitrous oxide which is an extremely inert molecule and a poor ligand. Groves and Roman have found that N O reacted with Ru"(TMP)(THF)2 in toluene to produce Ru (TMP)(0)2 . trans-dioxoRu(VI) complex can in turn epoxidize a suitable substrate such as tra/js-p-methyl styrene. This system was subsequently shown to be catalytic under appropriate conditions . 

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