Agent in the Vapor Phase

U.S. Surgeon General (4005) reported acrolein (propenal) to be one of the major toxic agents in the vapor phase of unaged cigarette MSS. 

It was noted that NDMA and NPYR were the most plentiful NNAs in cigarette smoke. NDM A is listed in this report as a toxic and tumorigenic agent in the vapor phase of cigarette smoke. Both NEMA (MSS delivery, 1 to 40 ng/cig) and NDEA (MSS delivery, 0.1 to 28 ng/cig) were reported as among the most potent environmental carcinogens of the NNAs. 

To reduce resist adhesion, a self-assembled monolayer of an oiganosilane release agent can be applied to the surface of the mold. Two processes can be used immersion and vapor-phase application. The vapor phase had fewer aggregates on the surface, because the lower density of the agent in the vapor-phase was not con-... 

Oxidation. Benzene can be oxidized to a number of different products. Strong oxidizing agents such as permanganate or dichromate oxidize benzene to carbon dioxide and water under rigorous conditions. Benzene can be selectively oxidized in the vapor phase to maleic anhydride. The reaction occurs in the presence of air with a promoted vanadium pentoxide catalyst (11). Prior to 1986, this process provided most of the world s maleic anhydride [108-31 -6] C4H2O2. Currendy maleic anhydride is manufactured from the air oxidation of / -butane also employing a vanadium pentoxide catalyst. 

Its principal military use is as a nitrating agent, either in the vapor phase or when dissolved in an inert solvent such as CCI4, for such substances as alkyl nitrites, cellulose and Nitrobenzene (Refs 2a, 8 13)... 

For treatment by the ZPU, a waste stream must be in the vapor phase at near-ambient pressure, at a temperature of less than 400°F, and relatively free of particulate matter. Each compound in the waste stream has unique requirements for destruction. Many compounds are destroyed with a low application of energy, while others require a stronger application. The dose required for a specific combination of contaminants must be determined experimentally. Moisture may either enhance or reduce system effectiveness depending on the mixture. Compounds that act as free-radical scavengers or reducing agents may diminish the process efficiency. Concentrations of vapors that produce temperatures above 400°F in the reaction chamber through exothermic reaction must be diluted to keep the temperature below 400°F. 

Uranium(VI) fluoride can react35 as a Lewis acid or an oxidizing agent with alcohols. In the vapor phase at 80 °C (note that this is considerably lower than the temperatures used in the examples given vide supra) it behaves as a Lewis acid and gives35 mixtures of the corresponding fluorides, alkenes and ethers (Table 1). 

Benzoquinone [106-51-4], C6H402 (quinone) has been reported as a by-product of benzene oxidation at 410—430°C. Benzene can be oxidized to phenols with hydrogen peroxide and reducing agents such as Fe(II) and Ti(II). Frequendy ferrous sulfate and hydrogen peroxide are used (Fenton s reagent), but yields are generally low (12) and the procedure is of limited utility. Benzene has also been oxidized in the vapor phase to phenol in low yield at 450—800°C in air without a catalyst (13). 

In the vapor phase, by direct grafting, a large number of authors have studied gamma-rays as the agent for creating active centers in the polyamidic backbone at room temperature. Dose irradiation ranges usuafly from 0.5 to 19Mrads. 

On the other hand, chemicals might be chosen as agents for generation of active centers in the polymeric backbone and grafting of monomer in the vapor phase. Ammonium persulfate and styrene (189), acrylic acid (190), butyl acrylate (191), potassium persulfate and n-butyl maleate or 2-ethyl hexyl acrylate (55,134) and ammonium ceric nitrate and methacrylic add (192) are examples of this method. Benzoyl peroxide deposited on polycaprolactam fibers initiates the grafting of styrene in vapor phase (193). 

Another reaction of commercial importance is the nitration of alkanes to give nitroparaffins. Such reactions usually are carried out in the vapor phase at elevated temperatures using nitric acid (HN03) or nitrogen tetroxide (N204) as the nitrating agent ... 

The SiO system is thus not simple, and its complexity increases with changes in stoichiometric composition. Oxygen in a small excess in the vapor phase results in slight oxidation. If reducing agents are present, for example if the surface of the apparatus has reducing properties, a small amount of silicon metal is produced. 

An azeotrope is a liquid mixture that has the same composition both in the liquid and in the vapor phase. This means that the components cannot be separated by conventional distillation. In such cases an entrainer or a third component is added to make the compositions of the liquid and the gas phases different. In the case of liquid-phase butane autoxidation (Section 8.4), 2-bu-tanone is separated as a pure component by adding entrainment agents such as ether to break the azeotrope the ketone forms with water. 

XeF2 also acts as a mild fluorinating agent for organic compounds for example, in solution or in the vapor phase benzene is converted into QH5F. The dissociation energy of XeF2 to XeF + F is ca. 252 kJ mol-1.11... 

More recently, Kiguchi reported benzylation of wood particles with the solvent dilution and vapor phase methods for reducing the amount of benzyl chloride in the etherification agent [12]. In the vapor phase benzylation below the boiling point of benzyl chloride, greatly thermoplasticized particles could be produced after 2-4 h at 140°C. However, in the solvent dilution method, higher reaction temperatures and longer reaction times than those in the ordinary liquid phase method were found to be necessary to obtain the thermoplasticized particles. 

---