Vapour-phase Complexes

An early approach to the problem of gas imperfection was to treat deviations from ideality as the result of chemical association. Consider a gaseous mixture of substances A and B that can react 

If A and B are the formal amounts of substance of each component and /iab is the amount of substance of complex AB, at equilibrium the application of the perfect gas law gives 

For a binary mixture of associating imperfect gases there will be physical as well as chemical contributions to Bjg. If the concentration of complex is small, 

Bia(phys.) is the interaction virial coeflScient arising from non-chemical interactions between the components and 5j8(chem.) is given by equation (58). Since ia(chem.) is negative, evidence for association would be an unusually large negative or a negative 

If 5i2 for an associating mixture is measured and jBi2(phys.) is calculated by a corresponding-states procedure, laCchem.) can be obtained by difference. The enthalpy change in the association reaction can also be derived from studies of the temperature dependence of J i2(chem.). 

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CUCI4 and (Me4N)2CoCl4. The Raman spectrum of the vapour-phase complex CuAl2Clg shows that this species has no centre of symmetry and that the co-ordination round copper is three or less a proposed structure is (97). The preparation of... 

In their study of association in ammonia + acetylene mixtures, Cheh, O Connell, and Prausnitz calculated the physical contribution to B12 from potentials that included hard-core as well as multipole interactions. The existence of vapour-phase complexes of ethylene with ammonia and methanol and of methanol with pentane has been inferred from virial coefficient data. King and co-workers have obtained association constants for COj with naphthalene, methanol, ethanol, and diethyl ether, and for HgO with CO2 and... 

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. 

Diels-Alder reactions, 4, 842 flash vapour phase pyrolysis, 4, 846 reactions with 6-dimethylaminofuKenov, 4, 844 reactions with JV,n-diphenylnitrone, 4, 841 reactions with mesitonitrile oxide, 4, 841 structure, 4, 715, 725 synthesis, 4, 725, 767-769, 930 theoretical methods, 4, 3 tricarbonyl iron complexes, 4, 847 dipole moments, 4, 716 n-directing effect, 4, 44 2,5-disubstituted synthesis, 4, 116-117 from l,3-dithiolylium-4-olates, 6, 826 electrocyclization, 4, 748-750 electron bombardment, 4, 739 electronic deformation, 4, 722-723 electronic structure, 4, 715 electrophilic substitution, 4, 43, 44, 717-719, 751 directing effects, 4, 752-753 fluorescence spectra, 4, 735-736 fluorinated derivatives, 4, 679 H NMR, 4, 731 Friedel-Crafts acylation, 4, 777 with fused six-membered heterocyclic rings, 4, 973-1036 fused small rings structure, 4, 720-721 gas phase UV spectrum, 4, 734 H NMR, 4, 7, 728-731, 939 solvent effects, 4, 730 substituent constants, 4, 731 halo... 

Today the sulphonation route is somewhat uneconomic and largely replaced by newer routes. Processes involving chlorination, such as the Raschig process, are used on a large scale commercially. A vapour phase reaction between benzene and hydrocholoric acid is carried out in the presence of catalysts such as an aluminium hydroxide-copper salt complex. Monochlorobenzene is formed and this is hydrolysed to phenol with water in the presence of catalysts at about 450°C, at the same time regenerating the hydrochloric acid. The phenol formed is extracted with benzene, separated from the latter by fractional distillation and purified by vacuum distillation. In recent years developments in this process have reduced the amount of by-product dichlorobenzene formed and also considerably increased the output rates. 

Not generally pyrophoric, unless dropped on vermiculite, the complex decomposes slowly in the liquid phase to generate considerable pressures of hydrogen. It appears much more stable in the vapour phase. 

An explosion and fire occurred in the pipework of a vessel in which dilute butadiene was stored under an inert atmosphere, generated by the combustion of fuel gas in a limited air supply. The inert gas, which contained up to 1.8% of oxygen and traces of oxides of nitrogen, reacted in the vapour phase over an extended period to produce concentrations of gummy material containing up to 64% of butadiene peroxide and 4.2% of a butadiene-nitrogen oxide complex. The deposits eventually decomposed explosively. 

In subsequent work the same supported catalysts were used in different reactor setups [20] (Figure 3.3). A vapour-phase reactor in which the supported catalyst was mounted on a bed was used for the hydroformylation of volatile alkenes such as cis-2-butene and trifluoropropene. The initial activities and selectivity s were similar to those of the homogeneous solutions, i.e. a TOF of 114 and 90% ee in the hydroformylation of trifluoropropene was reported. No rhodium was detected in the product phase, which means less then 0.8% of the loaded rhodium had leached. The results were, however, very sensitive to the conditions applied and, especially at longer reaction times, the catalyst decomposed. In a second approach the polymer supported complex was packed in a stainless steal column and installed in a continuous flow set-up. 

Mn(acac)3 reacts with ethylenediamine (L2) or other primary amines (L) to yield [Mn"(acac)2L2], which can also be prepared by the reaction of the amine or diamine with [Mn(acac)2(H20)2]. Allylamine reacts with [Mn(acac)2-(H20)2] in ether to give a second complex, [Mn(acac)2(H2NCH2==CH2)]2 which is dimeric both in the solid and vapour phases. This is the First example of a dinuclear manganese(ii) acetylacetonate complex. Thermodynamic data have been reported for the manganese(ii)-acetylacetone system in propan-1-ol-water. ... 

The mono-thiocarbamate complexes [Ni(OSCNR2)2] [R = Me, Et, Pr", Pr , or Bu", R2 = ( 112)4 or (CH2)j] have been prepared. The isopropyl complex is dimeric in the vapour phase and low-polymeric or cyclic oligomeric structures are proposed for the others. Bis-pyridine and bis-pyrrolidine adducts have been isolated. - ... 

Therefore, the appearance of the C—Li bands at unexpected low wavenumbers and their behaviour upon isotopic substitution demonstrate that these bands represent complex modes of vibration in polymeric molecules rather than simple C—Li stretching motions (Figure 1). It is well known that organolithium compounds are strongly associated in solution Furthermore, the C—Li bands occurred in the mulls and solution spectra of ethyllithium at similar positions to those in the vapour spectra, namely in the region from 570 to 340 cm (Table 1) . In benzene solution the bands were found at 560 and 398 cm for CiHs Li and at 538 and 382 cm for CiHs Li. This seems to confirm the previous finding of Berkowitz and coworkers that ethyllithium is polymeric even in the vapour phase. ... 

Bromination of pyridine is much easier than chlorination. Vapour phase bromination over pumice or charcoal has been studied extensively (B-67MI20500) and, as with chlorination, orientation varies with change in temperature. At 300 °C, pyridine yields chiefly 3-bromo-and 3,5-dibromo-pyridine (electrophilic attack), whilst at 500 °C 2-bromo- and 2,6-dibromo-pyridine predominate (free radical attack). At intermediate temperatures, mixtures of these products are found. Similarly, bromination of quinoline over pumice at 300 °C affords the 3-bromo product, but at higher temperatures (450 °C) the 2-bromo isomer is obtained (77HC(32-1)319). Mixtures of 3-bromo- and 3,5-dibromo-pyridine may be produced by heating a pyridine-bromine complex at 200 °C, by addition of bromine to pyridine hydrochloride under reflux, and by heating pyridine hydrochloride perbromide at 160-170 °C (B-67MI20500). 

In contrast to these vapour-phase reactions, it has been reported that ketones and aqueous ammonia (or ammonium acetate) in an autoclave give less complex mixtures of pyridines. Crotonaldehyde gives 5-ethyl-2-methylpyridine (570) in up to 59% yield, methyl vinyl ketone gives 2,3,4-trimethylpyridine (571) rather than 2,3,6-trimethylpyridine 1,3,3-trimethoxybutane has been used in place of methyl vinyl ketone (49JA2629). In some cases reverse aldol reactions occur (for example with benzalacetophenone) giving unwanted products. A similar reverse aldol is responsible for the production of triarylpyridines (572) when benzalacetophenones are treated with formamide and ammonium formate (73JA4891). 

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