Ethers Homogeneous equilibrium

The hole-size relationship between cations and crown ethers has been a part of the lore in the cation binding area for nearly two decades. Although, to our knowledge, no formal definition of this principle has ever been offered, the general concept seems to be that cation binding will be optimized when the cation diameter and macrocycle cavity size are identical. A simple consequence of this concept is the notion that 15-crown-5 is selective (binds more strongly) for Na+ over K+. We have measured the homogeneous (equilibrium) stability constants for the reaction... 

The earliest method of esterifying amino acids was developed by Fischer (5). By continuously passing hydrogen chloride gas into ethanolic suspensions of amino acids, the amino acids dissolve and the solution becomes homogeneous. After adding base to the reaction mixture, the resulting ester hydrochlorides can be isolated and extracted with ether. In principle, this is not a very efficient method since it is an equilibrium reaction. However, it can be made useful by... 

In reactive distillation, both the chemical reaction and the distillative separation of the product mixture are carried out simultaneously. This integrative strategy allows us to overcome chemical equilibrium limitations. For an exothermic reaction, the heat of reaction can be used directly for distillation. The term catalytic distillation is also used for such systems where a catalyst (homogeneous or heterogeneous) is used to accelerate the reaction. The synthesis of methyl acetate and MTBE (methyl tertiary butyl ether) are the two most prominent examples, where reactive distillation is used on an industrial scale (for MTBE see Section 4.10.8.1). It is beyond the scope of this textbook to discuss more details of this technology. Details can be found in the literature (Sundmacher and Kienle, 2002 Harmsen, 2007 Taylor and Krishna, 2000 Krishna, 2002 Stankiewicz, 2003). 

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