Practical considerations reactions

Saponification can proceed direcdy as a one-step reaction as shown above, or it can be achieved indirectly by a two-step reaction where the intermediate step generates fatty acids through simple hydrolysis of the fats and oils and the finishing step forms soap through the neutralization of the fatty acid with caustic soda. There are practical considerations which must be addressed when performing this reaction on a commercial scale. 

Volume of testing solution If exhaustion of corrosive constituents that may be present in minute concentrations and the accumulation of reaction products which may either accelerate or stifle further attack are to be avoided, the volume or mass of testing solution must be sufficiently large to avoid effects caused by these factors. In laboratory tests, however, practical considerations limit the volume of testing solution that can be provided for. A minimum of 250 ml of testing solution for each 6 - 3 cm of specimen area is suggested in NACE TM0169-76. 

Practical considerations limit, the scalability of this reaction due to the highly reactive and water sensitive intermediates formed. Furthermore, the time required for removal of large amounts of solvent in vacuo allows for the opening of the intermediate epoxide leading to diol formation. 

Practical considerations of unloading play a major role in batch-mass reactors. For "low conversion reactors, a suitably sized dump line must be chosen, based on acceptable N2 dump pressure in the reactor, or discharge pump capability, as well as consideration for limiting reaction in the line between batches. 

The parameter p (= 7(5 ) in gas-liquid sy.stems plays the same role as V/Aex in catalytic reactions. This parameter amounts to 10-40 for a gas and liquid in film contact, and increases to lO -lO" for gas bubbles dispersed in a liquid. If the Hatta number (see section 5.4.3) is low (below I) this indicates a slow reaction, and high values of p (e.g. bubble columns) should be chosen. For instantaneous reactions Ha > 100, enhancement factor E = 10-50) a low p should be selected with a high degree of gas-phase turbulence. The sulphonation of aromatics with gaseous SO3 is an instantaneous reaction and is controlled by gas-phase mass transfer. In commercial thin-film sulphonators, the liquid reactant flows down as a thin film (low p) in contact with a highly turbulent gas stream (high ka). A thin-film reactor was chosen instead of a liquid droplet system due to the desire to remove heat generated in the liquid phase as a result of the exothermic reaction. Similar considerations are valid for liquid-liquid systems. Sometimes, practical considerations prevail over the decisions dictated from a transport-reaction analysis. Corrosive liquids should always be in the dispersed phase to reduce contact with the reactor walls. Hazardous liquids are usually dispensed to reduce their hold-up, i.e. their inventory inside the reactor. 

A practical consideration in reaction modeling is choosing the extent to which reaction kinetics should be integrated into the calculations. On the one hand, kinetic... 

With respect to the practical considerations of gas flow and vacuum requirements, the PHPMS experiment might, upon cursory consideration, appear to be easily extended into the VHP region. That is, several MS-based analysis techniques routinely use ion source pressures of 1 atm. However, when an attempt to increase the pressure within a PHPMS ion source is made, the factors that do become problematic are those related to the subtle principles on which the method is based. Most importantly, the PHPMS method requires that the fundamental mode of diffusion be quickly established within the ion source after each e-beam pulse, so that all ions are transported to the walls in accordance with a simple first-order rate law while the IM reactions of interest are occurring. This ensures that a constant relationship exists between the ion density in the cell and the detected ion signal. The rates of the IM reactions can then be quantitatively determined from the observed time dependencies of the reactant ion signal because the contribution of diffusion to the time dependencies are well known and easily accounted for. 

The chemical reactions involving positron emitters have to be specially designed to take into account the short half life of the radionuclide, the limited number of labelled precursors and the sub-micromolar amounts of these precursors. Moreover, the reactions must be possible without any addition of the stable isotope (especially when ligands of receptors are synthesized). Several practical considerations that influence the design of positron-emitter radiotracers with a high specific radioactivity and their experimental handling have been reviewed [4,8,14-19]. 

In addition to these differences between excited-state and ground-state properties that influence chemical behaviour, there are some practical considerations that give photochemistry its distinctive features. In a thermal reaction, heat energy is normally supplied in an indiscriminate way to all the species in the reaction mixture— substrates, solvent and products—and this makes it difficult, for example, to prepare heat-sensitive compounds. In a photochemical reaction light can. in principle, be supplied selectively to just one... 

Given the knowledge that a particular reaction will proceed at a suitable rate, a host of practical considerations are necessary for satisfactory operation. 

The substantial difference in the heats of reaction of ethane, ethene, and ethyne with bromine is reflected in a very important practical consideration in handling ethyne (acetylene), namely its thermodynamic stability relative to solid carbon and hydrogen gas. Unlike ethane, both ethene and ethyne can be shown from bond energies to be unstable with respect to formation of solid carbon and gaseous hydrogen ... 

CHEMICAL THERMODYNAMICS OF CATION EXCHANGE REACTIONS THEORETICAL AND PRACTICAL CONSIDERATIONS... 

Ruinatscha R, Hollrigl V et al (2006) Productivity of selective electroenzymatic reduction and oxidation reactions theoretical and practical considerations. Adv Synth Catal 348 2015-2026... 

The choice of reactor will be very dependent on the requirements of the chemical reaction scheme, the relative importance of mixing and heat transfer, and practical considerations (e.g., the effect of solids in the process materials of construction flexibility). A comparison of the typical performance of different designs is given in Table 5. HEX Reactors are discussed in more depth in Chapter 4. 

Outline the practical considerations that need to be taken into account when selecting reactions for use in a synthetic pathway. 

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