VAPOUR PHASE

At 3130 A, oxygen decreased, to some extent, the quantum yield of the decomposition of 2-pentanone into C2H4 and The same was ob- 

Michael and Noyes observed a long-lived, 2-pentanone-sensitized biacetyl emission, the efficiency of which was lower at 2537 A than at 3130 A. A very weak sensitized emission was reported by them to occur in the photolysis of 2-hexanone, in the presence of biacetyl, at 3130 A, while at 2537 A emission was not observed. In the photolysis of 2-pentanone, biacetyl decreased the value of 0n at 3130 A (a Stern-Volmer type relation was obeyed), but exerted no influence at 2537 A . Biacetyl was foimd to have no influence on reaction II at either wavelength in the photolysis of 2-hexanone . 

On the basis of these results, Michael and Noyes concluded that it is the excited 

Ausloos and Rebbert carried out similar experiments with 2-pentanone at 3130 A. They also observed the sensitized emission and the quenching of primary process II in the presence of biacetyl. Moreover, they have demonstrated that the efficiency of the fluorescence, emitted by 2-pentanone, changed by no more than 2 % when biacetyl was added. This observation proves that, under the experimental conditions studied, only triplet-triplet energy transfer occurred, and that the triplet state of the ketone was the precursor, completely or at least partly, of primary process II. 

Primary step I The relative efficiencies of biacetyl and butene-2 in the quenching of reaction I were found to be not far from unity in the case of the ketones studied consequently, primary process I occurred from the high vibrational levels of the triplet state, possessing sufficient energy to induce efficiently the isomerization of butene-2. The efficiency of energy transfer to cw-butene-2 compared with that to biacetyl, measured in terms of reaction I, was found to be in the following order 2-pentanone 2-butanone acetone. It is possible that this order reflects the facility with which the vibrational energy of the donors may be made available to 

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It was first described in 1608 when it was sublimed out of gum benzoin. It also occurs in many other natural resins. Benzoic acid is manufactured by the air oxidation of toluene in the liquid phase at 150°C and 4-6 atm. in the presence of a cobalt catalyst by the partial decarboxylation of phthalic anhydride in either the liquid or vapour phase in the presence of water by the hydrolysis of benzotrichloride (from the chlorination of toluene) in the presence of zinc chloride at 100°C. 

C4H8O, CH3COCH2CH3. Colourless liquid with a pleasant odour, b.p. 80°C. It occurs with propanone in the products of the destructive distillation of wood. Manufactured by the liquid or vapour phase dehydrogenation of 2-butanol over a catalyst. Used as a solvent, particularly for vinyl and acrylic resins, and for nitrocellulose and cellulose acetate, also for the dewaxing of lubricating oils. U.S. production 1978 300 000 tonnes. 

Obtained synthetically by one of the following processes fusion of sodium ben-zenesulphonate with NaOH to give sodium phenate hydrolysis of chlorobenzene by dilute NaOH at 400 C and 300atm. to give sodium phenate (Dow process) catalytic vapour-phase reaction of steam and chlorobenzene at 500°C (Raschig process) direct oxidation of cumene (isopropylbenzene) to the hydroperoxide, followed by acid cleavage lo propanone and phenol catalytic liquid-phase oxidation of toluene to benzoic acid and then phenol. Where the phenate is formed, phenol is liberated by acidification. 

Silicon monoxide, SiO. Formed Si02 plus C in electric furnace. The impure brown powder is used as a pigment and abrasive (Monex). Stable in vapour phase (Si plus Si02). 

Miblimation The volatilization of a solid substance into the vapour phase without passing through the liquid phase. Also used to describe the process of purification in which the vapour is condensed directly from the vapour phase to a solid (on a cold-finger often cooled by refrigerant). In the latter case this substance may melt during the initial vaporization. Used for purification. 

Trichloroethylene is manufactured by the dehydrochlorination of tetrachloroelhane derived from the chlorination of ethyne with lime or by vapour phase cracking. 

In this section we describe hydrocarbon processing in preparation for evacuation, either from a production platform or land based facilities. In simple terms this means splitting the hydrocarbon well stream into liquid and vapour phases and treating each phase so... 

When oil and gas are produced simultaneously into a separator a certain amount (mass fraction) of each component (e.g. butane) will be in the vapour phase and the rest in the liquid phase. This can be described using phase diagrams (such as those described in section 4.2) which describe the behaviour of multi-component mixtures at various temperatures and pressures. However to determine how much of each component goes into the gas or liquid phase the equilibrium constants (or equilibrium vapour liquid ratios) K must be known. 

Y - Mol fraction of each component in the vapour phase X - Mol fraction of each component in the liquid phase... 

Preparation of films for sufficiently volatile molecules can also be perfonned by evaporating tire molecules in vacuum (gas-phase deposition) or by tire use of a desiccator which contains tire substrate and tire dilute solution in a vessel separately and which is evacuated to 0.1 mbar and kept under vacuum for several hours ( 24 h). This also results in a vapour-phase-like deposition of tire molecules onto tire substrates. 

These molecules exist in the solid halides, explaining the low melting points of these halides, and also in the vapour phase at temperatures not too far above the boiling point. At higher temperatures, however, dissociation into trigonal planar monomers, analogous to the boron halides, occurs. 

The action of this and other anti-bumping devices e.g., minute carborundum chips) is dependent upon the fact that the transformation of a superheated liquid into the vapour will take place immediately if a vapour phase e.g., any inert gas) is introduced. The effect may be compared with that produced by the introduction of a small quantity of a solid phaM into a supercooled liquid, e.g., of ice into supercooled water. 

The vapour pressures are proportional to the mol fractions in the vapour phase, hence the composition of this phase will be given by ... 

Thus a solution containing mol fractions of 0-25 and 0-75 of A and B respectively is in equilibrium with a vapour containing 16-7 and 83 -3 mol per cent, of A and B respectively. The component B with the higher vapour pressure is relatively more concentrated in the vapour phase than in the liquid phase. 

The breaking up of azeotropic mixtures. The behaviour of constant boiling point mixtures simulates that of a pure compound, because the composition of the liquid phase is identical with that of the vapour phase. The composition, however, depends upon the pressure at which the distillation is conducted and also rarely corresponds to stoichiometric proportions. The methods adopted in practice will of necessity depend upon the nature of the components of the binary azeotropic mixture, and include —... 

The relative weights of the two components of the vapour phase will be idaitical with the relative weights in the distillate, i.e., the weights of the two liquids collecting in the receiver are directly proportional to their vapour pressures and their molecular weights. 

The simpler nitrop>arafIins (nitromethane, nitroethane, 1- and 2-nitroproj)ane) are now cheap commercial products. They are obtained by the vapour phase nitration of the hydrocarbons a gaseous mixture of two mols of hydrocarbon and 1 mol of nitric acid vapour is passed through a narrow reaction tube at 420-476°. Thus with methane at 476° a 13 per cent, conversion into nitro methane is obtained ethane at 420° gives a 9 1 mixture of nitroethane (b.p. 114°) and nitromethane (b.p. 102°) propane at 420° afifords a 21 per cent, yield of a complex mixture of 1- (b.p. 130-6°) and 2-nitropropane (b.p. 120°), nitroethane and nitromethane, which are separated by fractional distillation. 

Commercially, maleic anhydride is prepared more cheaply by the catalytic vapour phase oxidation (in the presence of vanadium pentoxide at about 400°) of benzene with atmospheric oxygen ... 

Figure 1.4. Temperature dependence of the change in Gihhs energy, enthalpy and entropy upon transfer of ethane and butane from the gas phase to water. The data refer to transfer from the vapour phase at 0.101 MPa to a hypothetical solution of unit mole fraction and are taken from ref. 125.

More information has appeared concerning the nature of the side reactions, such as acetoxylation, which occur when certain methylated aromatic hydrocarbons are treated with mixtures prepared from nitric acid and acetic anhydride. Blackstock, Fischer, Richards, Vaughan and Wright have provided excellent evidence in support of a suggested ( 5.3.5) addition-elimination route towards 3,4-dimethylphenyl acetate in the reaction of o-xylene. Two intermediates were isolated, both of which gave rise to 3,4-dimethylphenyl acetate in aqueous acidic media and when subjected to vapour phase chromatography. One was positively identified, by ultraviolet, infra-red, n.m.r., and mass spectrometric studies, as the compound (l). The other was less stable and less well identified, but could be (ll). 

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