Pseudo-compounds

The actual Russian standards allow presentation of hydrocarbon components of UGC as individual compounds only for C -C hydrocai bons. The rest is described as pseudo-compound C,, although its content may reach 60 % m/m. Apparently, the detailed determination of composition of hydrocarbons C, in UGC allows essentially to raise quality of both its processing and its record. The best method for the determination of heavy hydrocai bons is capillary gas chromatography. Typical approach is based on preliminary sepai ation of UGC samples to gaseous and liquid phases. 

He suggested a nomenclature for the terpenes by which those compounds which contain a double linkage between the nucleus and the side chain should be called pseudo-compounds, whilst the compounds with the double linkage in the nucleus should be the ortho-compounds. He suggested the following formulae —... 

It is worth noting that some cyclic molecules play an important role in the mechanism. Another interesting feature results from the use of lumped compounds. The lumping of different species into a single pseudocompound causes a reduction in the complexity of the reacting system. For example, the 4 isomers of the branched C6 paraffins are lumped into a single pseudo-compound the 12 alkylbenzenes from C9 to C2o are described by three pseudo-compounds, C9, C1S and C20, etc. 

These lumping processes have allowed Goossens et al. to reduce the number of elementary processes from 2000 to 500 final processes involve 18 chain-propagating radicals and 85 molecular species or pseudo-compounds from H2 to C22. 

Pseudo Compounds.—We have then another. case of tautomerism the compounds in this case being termed pseudo compounds, i.e., compounds apparently different but which exist in the free condition in only one structural form, molecular rearrangement occurring between them. 

The aci-compound of phenylnitromethane in acid solution slowly changes into the pseudo-compound. At the same time its color goes from yellow to almost colorless. Hantzsch showed that the aci- and pseudo-compounds of the nitrophenols had the following general structures ... 

He suggested that in acid solution the aci-compound is not completely converted into the pseudo-compound, but that these substances are in equilibrium with each other ... 

Hantzsch has adduced as further evidence for the existence of these aci- and pseudo-compounds the fact that he has prepared esters of both types of substances, the aci-ester being yellow and the other being colorless. 

The same investigator has proposed a similar explanation for the relationship between pseudo-hases and 6aso-compounds. A salt of crystal violet is colored violet in alkaline solution, and its conductivity is high. The solution becomes colorless after standing for some time, and the conductivity diminishes to a minimum value. The baso-compound, which is a strong base and is colored violet, possesses a structure different from that of the colorless pseudo-compound ... 

The simpler equation (4) embodies the Ostwald conception with the difference that Km is not the true dissociation constant but the apparerd constant of the indicator since it represents the product of the true dissociation constant and the equilibrium constant for the normal and aci-forms. The latter equilibrium favors the normal compound in the case of p-nitrophenol so that this substance appears to be a very weak acid. With o-nitro-phenol, however, the existence of the aci-form is favored so that this compound behaves as a stronger acid. The ratio of aci to normal is so large in the case of picric acid that relatively much of the aci- or ionogen form, as compared with the pseudo-compound, is present in aqueous solution. Consequently this substance is a rather strong acid. As the apparent dissociation constant increases, the intensity of the yellow color of aqueous solutions must likewise grow because more of the aci-form will be found in solution. This statement can be confirmed easily. Picric acid in water solutions is yellow, but colorless in organic solvents due to the predominance of the pseudo-form. 

We see that here too the dissociation constant of the indicator is merely an apparent value which is composed of the true dissociation constant and the equilibrium constant between the aci- and pseudo-compounds. The equilibrium between Q and L in water solutions is such that the liquid appears to be colorless. Displacement of the equilibrium by addition of alkali produces a red color. 

The chief point of departure from the explanation of Ostwald consists in not having to say that the color of the ions differs from that of the pseudo-compounds. It is the ionogenic form which is differently colored. We see here the connection with the chromophore theory which states that the ionogen form and the normal form have different structures. 

The method of solution analysis is based on differences in solubility of the vacuum residue compounds (pseudo-compounds) in different solvents. Figure 8.8 shows an example of the scheme for solution analysis in which the following solvents are used ... 

Four fractions of pseudo-compounds are obtained by solution analysis of crude oil residue or its cracked product. During solution analysis of the cracking product from thermal treatment of vacuum residue or mixtures of vacuum residue and plastics (such mixtures were used in our investigation), a first step of solution analysis is soxhlet extraction. In the soxhlet extractor, the liquid/solid product is extracted with fresh warm solvent (THF) that does not contain the extract. This can increase the extraction rate, as the sample is contacting fresh warm solvent. The sample is placed inside a cellulose thimble and placed in the extractor. The extractor is connected to a flask containing the extraction solvent, and a condenser is connected above the extractor. The solvent is boiled, and the extractor has a bypass arm that the vapor passes through to reach the condenser, where it condenses and drips into the sample in the thimble. Once the solvent reaches the top of the siphon arm, the solvent and extract are siphoned back into the lower flask. The solvent reboils, and the cycle is repeated until the sample is completely extracted, and the extract is in the lower flask. 

Similar to solution analysis, the method of coagulation analysis is based on the different solubilities of vacuum residue compounds (pseudo-compounds) in the different solvents. The following solvents were used for the analysis of feedstock ... 

All ionones, irones, and methylionones, as well as the corresponding pseudo compounds (their synthetic acyclic precursors), are slightly viscous, yellowish liquids. Commercial irones and methylionones are mixtures of isomers that are named according to their main component. Their composition varies with the method used to prepare and cyclize the pseudocompound and fluctuates considerably between different manufacturers. 

As shown in Table 2 the liquid fraction descriptions in most multi-component kinetic schemes are very limited. In most cases (Behar et al. 1997 EspitaHe et al. 1988 lingerer et al. 1990) the liquid fraction is described by two compound classes (i.e. two pseudo-compounds for the PVT simulator). The multi-component kinetics of Abu-Ali et al. (1999) and Vanden-broucke et al. (1999) have a higher resolution of the liquid fraction (five and six pseudocompounds respectively) but many of these compound groups are very similar with respect to their physical properties, and therefore do not describe the liquid composition adequately for phase behaviour calculations. 

In that work, the kinetic equation obtained for the whole range of compositions is based on a LHHW mechanism in which IB and MeOH, both adsorbed on the resin, react to form MTBE. The rate-controlling step is surface reaction. As a simplification in the activities calculation, the authors consider that the reaction mixture is composed by three compounds methanol, MTBE and a C4 pseudo-compound that includes all hydrocarbons. In the absence of product, the proposed kinetic equation is... 

Empirical methods are based on fits of partitioning data (generally chamber observations) to identify a set of pseudo-compounds with different abundances, which can then be used to simulate the gas-particle partitioning of OA. A major challenge with this approach is whether the properties of these pseudo-compounds are constant as one extrapolates away from the conditions under which the experiment was conducted. To help minimize these errors, it is critical to condition the partitioning experiments over as much atmospherically relevant space as possible. 

---