Condensed hydrolysis

A Hquid-phase isophorone process is depicted ia Figure 4 (83). A mixture of acetone, water, and potassium hydroxide (0.1%) are fed to a pressure column which operates at head conditions of 205°C and 3.5 MPa (- 500 psi). Acetone condensation reactions occur on the upper trays, high boiling products move down the column, and unreacted acetone is distilled overhead ia a water—acetone a2eotrope which is recycled to the column as reflux. In the lower section of the column, water and alkaH promote hydrolysis of reaction by-products to produce both isophorone and recyclable acetone. Acetone conversion is typically ia the range 6—10% and about 70% yield of isophorone is obtained. Condensation—hydrolysis technology (195—198), and other Hquid-phase production processes have been reported (199—205). 

Phosphate condensation reactions play an essential role in metabolism. Recall from Section 14.6 that the conversion of adenosine diphosphate (ADP) to adenosine triphosphate (ATP) requires an input of free energy ADP -I-H3 PO4 ATP +H2O AG° — +30.6kJ As also described in that section, ATP serves as a major biochemical energy source, releasing energy in the reverse, hydrolysis, reaction. The ease of interchanging O—H and O—P bonds probably accounts for the fact that nature chose a phosphate condensation/hydrolysis reaction for energy storage and transport. 

In a faster, selective and cleaner applications of the microwave-accelerated reactions, Stone-Elander et al. have synthesized a variety of radiolabeled (with 3H, 11C, and 19F) organic compounds via the nucleophilic aromatic and aliphatic substitution reactions, esterifications, condensations, hydrolysis and complexation reactions using monomodal MW cavities on microscale [121]. A substantially reduced level of radioactive waste is generated in these procedures that are discussed, at length, in Chapt. 13 [122]. 

Condensation-cured model systems, of silicone networks, 22 569 Condensation energy, 23 826 Condensation-hydrolysis technology,... 

What sort of chemical reactions are occurring, for example, oxidation, condensation, hydrolysis. 

FIGURE 7.4 Of the 16 chemistry topics examined (1-16) on the final exam, overall the POGIL students had more correct responses to the same topics than their L-I counterparts. Some topics did not appear on all the POGIL exams. Asterisks indicate topics that were asked every semester and compared to the L-I group. The topics included a solution problem (1), Lewis structures (2), chiral center identification (3), salt dissociation (4), neutralization (5), acid-base equilibrium (6), radioactive half-life (7), isomerism (8), ionic compounds (9), biological condensation/hydrolysis (10), intermolecular forces (11), functional group identification (12), salt formation (13), biomolecule identification (14), LeChatelier s principle (15), and physical/chemical property (16). 

In the reaction of Figure 12.19, the alkoxide formed in this step deprotonates a carboxylic acid (cis-1 —> K), whereas in Figure 12.18 an iminium ion is deprotonated (B — C). Accordingly, different chemoselectivities are observed Figure 12.19 shows an enamine-mediated aldol addition, and Figure 12.18 presents an enamine-mediated aldol condensation. Hydrolysis of the iminium ion K in Figure 12.19 leads to the formation of the aldol addition products B and the amine which, together with the still unconsumed substrate A, forms the new enam-ine C, to start the catalytic cycle anew. 

This catalytic cascade was first realized using propanal, nitrostyrene and cinnamaldehyde in the presence of catalytic amounts of (9TMS-protected diphenylprolinol ((.S )-71,20 mol%), which is capable of catalyzing each step of this triple cascade. In the first step, the catalyst (S)-71 activates component A by enamine formation, which then selectively adds to the nitroalkene B in a Michael-type reaction (Hayashi et al. 2005). The following hydrolysis liberates the catalyst, which is now able to form the iminium ion of the a, 3-unsaturated aldehyde C to accomplish in the second step the conjugate addition of the nitroalkane (Prieto et al. 2005). In the subsequent third step, a further enamine reactivity of the proposed intermediate leads to an intramolecular aldol condensation. Hydrolysis returns the catalyst for further cycles and releases the desired tetrasubstituted cyclohexene carbaldehyde 72 (Fig. 8) (Enders and Hiittl 2006). 

Citrate is a key intermediate of the tricarboxylic acid (TCA) cycle, also known as the Krebs cycle, in the central metabolism of cells. (The set of reactions of the TCA cycle will be considered in some detail in Chapter 6.) One reaction in the cycle is the combination of oxaloacetate (OAA) and the acetyl group from acetyl coenzyme A (ACCOA), in the presence of H2O, to form citrate (CIT), thiol coenzyme A (COASH), and hydrogen ion (H+). The chemical reference reaction for this aldol condensation-hydrolysis reaction catalyzed by citrate synthase is ... 

In the early 1960s, seminal work by Jencks and coworkers demonstrated that formation and hydrolysis of C=N bonds were proceeding via a carbinolamine intermediate, thus leading to a more general mechanism of addition reactions on carbonyl groups [17-19]. The dynamic nature of the reaction of imine formation can be exploited to drive the equilibrium either forward or backwards. Since the reaction involves the loss of a molecule of water, adding or removing water from the reaction mixture proved an efficient way to shift the equilibrium in either direction. The responsive behavior of imines to external stimuli makes the reversible reaction of imine formation perfectly suited for DCC experiments [20], Thermodynamically controlled reactions based on imine chemistry include (1) imine condensation/hydrolysis, (2) transiminations, and (3) imine-metathesis reactions... 

Fig. 1 Three examples of reversible reactions involving imines (i) inline condensation/hydrolysis (ii) transimination, and (iii) imine metathesis reaction...

PTMO oligomers are taken into account, along with the size of clusters that may form from the highly condensed hydrolysis products of TEOS (7). 

Alumina is probably the most commonly used adsorbent. It has the advantages of being white, insoluble, reasonably chemically inert, a good adsorbent for many compounds, and readily available. Ordinary alumina often contains some sodium carbonate or sodium bicarbonate, and in many cases this is a disadvantage since the base may promote aldol condensations, hydrolysis of esters and lactones, and similar reactions. The basic impurities may be removed by washing the alumina... 

Birch reduction of the bisketal of 54 to the enone 55, followed by Eschenmoser cleavage of the derived epoxyketone with aminodiphenylaziridine, yielded the acetylide 56. Ring B was formed by aldol condensation, hydrolysis of the acetylene to the methyl ketone, and selective ketalization to give 57. The extensive manipulation of protecting groups resulted in a somewhat unsatisfactory overall yield of 14%. 

Due to condensation/hydrolysis reactions also dimers and oligomers are present ... 

That said, metabolic interconversion of the amine backbone linkage of the ANPs would require oxidation, and thus would be a redox process rather than condensation/hydrolysis. Water remains a necessity for life and certainly life on Earth exploits condensation in the linkages of the nucleic acid monomers (phosphoester bonds), the amides of polypeptides, and the acetals of polysaccharides, and utilizes the reverse reaction of hydrolysis for metaboUsm. Therefore we have sought to extend the principles learned with the amine backbones to possible backbone chemistries that allow equilibrium control of template-directed polymerization through condensation and hydrolysis reactions. 

Total syntheses of this group also include the synthesis of 11-oxo-steroids described in the patent literature [1066] (Scheme 118). The starting material used was the cyanoester (413) formed by the condensation of acetoacetic and cyanoacetic esters. The successive addition of hydrogen cyanide and acrylonitrile, hydrolysis, decarboxylation, and esterification of the product led to the tetraester (414). Dieckmann condensation, hydrolysis, decarboxylation, and esterification gave the monocyclic... 

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