Condensation reactions, reversible

The highlighted section reacts with water in a reverse condensation reaction to give the monomer that polymerizes with glycerol. 

Setting (AA — BB) = Mx, we can write the general reversible condensation reaction... 

Eslertt, like aldehydes and hetones. nre weakly acidic. When an ester Mritli an ide, a reversible condensation reaction occurs to yield a /J-keto este-r. Par example, ethyl acetate yields ethyl acetoacetate on treatment with base. This reaction between two ester molecules is known an the Cliusen condensation reaction, f Well use ethyl esters for coitsistency, but other esters will also work. I... 

When acetaldehyde is treated with a base, such as sodium ethoxide or sodium hydroxide, a rapid and reversible condensation reaction occurs. The product is a /3-hydroxy aldehyde, or aldol (oidehyde -l- alcohoZ). 

The synthons of porphyrin syntheses are the pyrroles, which in turn must be made from 1,4-difunctional synthons. These carbon skeletons are available by an aldol-type condensation of the enol of a 1,3-diketone with an a-nitrosylated acetoacetate (Knorr pyrrole synthesis. Scheme 1.3.4). The final reductive ring closure by Schiff base formation is again a reversible condensation reaction. After dehydration, however, a stable 7i-electron sextet is formed, which gives the resulting pyrrole aromatic stability. Hydrolysis of this enamine can now only occur in very strong acid. In water of modest acidity or basicity it is perfectly stable. 

The coupling of (irreversible) oxidation reactions with (reversible) condensation reactions in the biological luminescence cycle exemplifies a major advantage of living systems over synkinetic light reaction chains. Only in biological systems is the renewal of decomposed dyes realized. All useful model reactions developed so far are limited to totally reversible reactions of the dyes, whereas nature also optimizes the interplay between irreversible degradation and biosynthetic reactions. 

PV is a promising option to enhance the conversion of reversible condensation reactions in which water is formed as a by-product. Peters et al. (2005) prepared composite catalytic membranes by a dip-coating technique. Composite catalytic membranes have been prepared by applying a zeolite coating on top of ceramic hf silica membranes. In the PV-assisted esterification reaction, the catalytic manbrane was able to couple catalytic activity and water removal. A reactor evaluation proved that the outlet conversion of the catalytic PV-assisted esterification reaction exceeded the conversion of a conventional inert PV membrane reactor, with the same loading of catalyst dispersed in the bulk liquid. Further, the performance of the zeolite-coated PV membranes can be increased by optimization of the catalytic layer thickness or by an increase in catalytic activity. 

Polymers with intrinsic microporosity, abbreviated as PIMs, were developed for the first time by McKeown and Budd. The general design strategy involves incorporation of extended aromatic components within a rigid polymer network in order to imitate the structural layout of graphene sheets of activated carbons.The principle behind the synthesis of PIMs employs non-reversible condensation reactions to form polymers. These polymers cannot efficiently fill the space and pack together due to components that are rigid and ladder-like, and thus force the backbone of the polymer to twist or turn. 

A more complex equation is needed when hydrolysis is equilibrated by the reverse condensation reaction (see next paragraph). When Equation [12.34] is an acceptable approximation, the integration of Equation [12.33], for a symmetric sheet of thickness L, gives ... 

Functional groups capable of undergoing reversible condensation reactions... 

Like aldehydes and ketones, esters also exhibit reversible condensation reactions. 

Aldehydes and ketones undergo reversible condensation reactions with primary amines to give products containing an azomethine,... 

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