Chlorinated aromatics, replacement

In catalytic hydrogenation, chlorine is replaced by hydrogen in chlorinated aromatic hydrocarbons (equations 41 and 42), phenols (equation 43), amines (equation 44), carboxylic acids (equation 45), and nitro compounds (equation 46). - Hydrogenolysis of chlorine in chloronitro compounds takes precedence over reduction of nitro groups, provided that contact with the halogen-free product is not too long. The reaction is achieved using palladium on carbon or tetrakis(triphenylphos-... 

In aromatic heterocycles, chlorine is replaced by hydrogen in catalytic vapor phase hydrogenation over palladium on charcoal at 280 °C. 3,5-Dichlorotrifluoropyridine affords 2,4,6-trifluoropyridine in 75% yield. ... 

The environmental problems associated with chlorinated aromatics continue to stimulate Interest in reactions involving photochemical replacement of chlorine by hydrogen. The efficiency of photochemical dechlorination of some... 

Hydroxide Ions. The photolysis of propanil, 4-CPA, and other chlorinated aromatic pesticides in water also can generate phenols through the replacement of halogen by hydroxyl groups (39, 41). Oxygen does not seem to have an important part in this reaction, if it is involved at all, and observation that the replacement proceeds upon irradiation... 

OXSOL 100 is a purified grade of p-chlorobenzotrifluoride (PCBTF) with the characteristic odor of chlorinated aromatic solvents. OXSOL 100 is a clear water-white liquid with solvency characteristics similar to the cleissiceil chlorinated and fluorinated solvents. PCBTF has been commercially produced for over thirty years eis a chemiceil intermediate. OXSOL 100 has been used as a solvent since 1992 eis a replacement for solvents with Ozone Depletion Potential (ODP), Volatile Organic Compounds (VOC) and Hazardous Air Polluteuits (HAP). 

One example of feedstock replacement that has been applied commercially is the work of Stem and co-workers (19-21) at the Monsanto Corporation in the synthesis of a variety of aromatic amines. By using nucleophilic aromatic substitution for hydrogen. Stem was able to obviate the need for the use of a chlorinated aromatic in the synthetic pathway. Certain chlorinated aromatics are known to be persistent bioaccumulators and to possess other environmental concerns this research in feedstock replacement resulted in the removal of that concern. 

Glutathione-S-transfer was mentioned above as a way of modification of epoxides however, it can also replace chlorine in chlorinated aromatic hydrocarbons. The... 

There is now information available on combustion and pyrolysis products for eight of the fourteen PCB replacement fluids listed in Table 1. Of the eight materials which have been tested (polydimethylsiloxane, RTEmp, phthalates, phenylxylylethane, dixylylethane, isopropylbiphenyl, n-propylbiphenyl, and chlorinated benzenes), the chlorobenzenes appear to present the greatest human health hazard in the event of fire. This is primarily due to the formation of chlorinated dioxins, chlorinated furans, and other chlorinated aromatics during combustion. The other seven fluids appear to be better choices as PCB substitutes, with the nonaromatic fluids perhaps posing the lowest health risk. 

The influence of NO on the performance of V0x/Ti02, V0x-W0x/Ti02 and VOx-MoOx/Ti02 was investigated in the combustion of ChB. NO proved to induce an increase in ChB conversion, however, this only occurred if O2 was present and was maximized when the catalyst contained W or Mo. The suggested mechanism for this effect was for NO to first be oxidized to NO2, mainly on WOx and MoOx then, NO2 replaces or assists O2 in the re-oxidation step of the VOx phase (as described by Mars and van Krevelen ), thus speeding up the oxidation cycle, which macroscopically corresponds to the increase in ChB conversion. The reaction scheme is represented in Fig. 4.6. It appears that NO is definitively not a poison on the contrary, it acts as a dopant of chlorinated aromatics combustion on VOx-based catalysts. 

The aHphatic iodine derivatives are usually prepared by reaction of an alcohol with hydroiodic acid or phosphoms trHodide by reaction of iodine, an alcohol, and red phosphoms addition of iodine monochloride, monobromide, or iodine to an olefin replacement reaction by heating the chlorine or bromine compound with an alkaH iodide ia a suitable solvent and the reaction of triphenyl phosphite with methyl iodide and an alcohol. The aromatic iodine derivatives are prepared by reacting iodine and the aromatic system with oxidising agents such as nitric acid, filming sulfuric acid, or mercuric oxide. 

The principal use of antimony pentafluoride is as a fluorinating agent. It readily replaces all chlorines with fluorine in organic compounds, and it fluorinates double bonds and aromatic rings. 

Some high-valency fluorides applied at moderate temperatures are capable of replacing individual hydrogens in aromatic rings Thus benzene affords fluoro benzene on treatment with silver difluoride [/] and with chlorine pentafluoride [2] (equations 1 and 2)... 

When reacted with dimethyl acetylenedicarboxylate, the amines produced ben-zotriazolylaminobutendioates 188 accompanied by A-benzotriazolyl substituted 2-pyridones only in the case of 5-amino-2-methyl-2//-benzotriazole, the triazolo-9,10-dihydrobenzo[d]azepine and an unusual cyclization product, triazolo-2-oxindole (convertible into 2-methyltriazolo[4,5-/]carbostyril-9-carboxylate) were formed. The quinolones 189 were aromatized to chloroesters 190 these in turn were hydrolyzed to chloroacids 191 and decarboxylated to 9-chlorotriazolo[4, 5-/]quinolines 192 (Scheme 58) (93H259). The chlorine atom could be replaced with 17 various secondary amines to give the corresponding 9-aminoalkyl(aryl) derivatives 193, some of which exhibit both cell selectivity and tumor growth inhibition activity at concentrations between 10 and 10 " M (95FA47). 

Replacement of the aromatic hydroxyl groups in isoproterenol by chlorine again causes a marked shift in biologic activity. 

Diuretic activity can be retained in the face of replacement of one of the sulfonamide groups by a carboxylic acid or amide. Reaction of the dichlorobenzoic acid, 174, with chlorsulfonic acid gives the sulfonyl chloride, 175 this is then converted to the amide (176). Reaction of that compound with furfuryl ine leads to nucleophilic aromatic displacement of the highly activated chlorine at the 2 position. There is thus obtained the very potent diuretic furosemide (177). ... 

Chlorinated rubber is soluble in aromatic solvents, and paints made from it dry by solvent evaporation alone. In contrast to the vinyls, there is less difficulty in formulating systems that are suitable for brush application. It has excellent resistance to a wide range of chemicals and to water, but as it is extremely brittle it needs to be plasticised. To preserve chemical resistance it is necessary to use inert plasticisers such as chlorinated paraffin wax. Due to the presence of ozone depleting solvents, chlorinated rubber coatings are being phased out and largely replaced by vinyl acrylic coatings which have very similar performance and can be formulated from lower aromatic or aliphatic solvents. 

Replacement, of aromatic chlorine atoms, by amino groups using ammonia, 40, 97... 

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