Reflux process

Figure 5 shows the calculated heat Input and cooling coll heat removal rates In KW, the latter calculated from water flow and temperature differential by the computer when logging. As Is typical with non-reflux processes, actual heat Is within 5% of expected from the theoretical heat of reaction. 

Because of these precursor modification reactions, the process chemistry of chelate processes is as complex, or more so, than that involved in sol-gel processes.78 However, it is typical for chelate processes that some control of process chemistry is sacrificed in return for more expedient solution preparation. For example, the hour-long (or longer) reflux processes that have been historically used in 2-methoxyethanol based sol-gel processing of ferroelectric films are not used. Rather, the entire solution preparation procedure is generally completed within one hour, with only the initial phase of the procedure being carried out under dry box and inert atmosphere conditions. Once the chelation reaction(s) has occurred, the hydrolysis sensitivity of the precursor solution is reduced to the point where the remaining process chemistry may be carried out under ambient conditions.46... 

Chemical separations are often either a question of equilibrium established in two immiscible phases across the contact between the two phases. In the case of true distillation, the equilibrium is established in the reflux process where the condensed material returning to the pot is in contact with the vapor rising from the pot. It is a gas-liquid interface. In an extraction, the equilibrium is established by motion of the solute molecules across the interface between the immiscible layers. It is a liquid-liquid, interface. If one adds a finely divided solid to a liquid phase and molecules are then distributed in equilibrium between the solid surface and the liquid, it is a liquid-solid interface (Table 1). 

Sulfur blue dyes are often made using an organic solvent such as n-butanol, in what is known as the solvent reflux process. Examples are C.I. Sulfur Blue 9 and Sulfur Blue 13. In this case, intermediate structures are indophenols (e.g., 55). See Fig. 13.133. Similarly, sulfur dyes containing benzothiazine groups can be made from... 

Fig. 13.133. Synthesis of blue dyes by the solvent reflux process.

Reflux is one of the most common techniques you will encounter in your chemistry laboratory classes. Since many reactions between covalent compounds are slow processes rather than instantaneous reactions, prolonged heating forces the equilibrium to give an acceptable amount of product. In the reflux process, the reactants are dissolved or suspended in a suitable solvent, the solvent is boiled and then condensed so that it returns to the reaction flask. Once set up, a reaction carried out under reflux can be run for minutes, hours or even days to promote the required reaction. The basic components for a reflux apparatus are ... 

Choose a condenser of appropriate size and type so that it w/ill condense the volume of vapour formed in the reflux process. For example, do not... 

Choose a condenser of appropriate size and type so that it will condense the volume of vapour formed in the reflux process. For example, do not use a small condenser with a 14/23 joint on a 250 mL flask, since it will not cope with the volume of vapour to be condensed, or a large condenser on a small flask, where all the solvent may be converted into vapour before condensation occurs. 

Thermally induced reactions of this type [38, 39] are shown in Schemes IV-20 and IV-21 (in cases of cyclopentane and cyclohexane jt-cyclopentadienyl and i-benzenc complexes can be obtained). Continuous removal of molecular hydrogen evolved in the reflux process displaces the equilibrium (IV.3) toward olefin. Hydrogen evolving in the course of the dehydrogenation can be efficiently removed if the reaction is carried out by refluxing in perfluorodecane or by bubbling argon [38c]. 

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