Hydrogen bonding adipic acid

Fig. 20 View of caffeine-adipic acid tiimers along the crystaUographic plane (1-2 0). The trimers are linked via hydrogen-bonded adipic acid molecules into molecular tapes...

On the other hand, the methoxyester results from MeOH attack on coordinated double bond, followed by methoxycarbonylation (Scheme 11). In both cases, the formation of 7r-allylpalladium complexes directs the regio-chemistry of the process. By optimizing the reaction conditions, it has been possible to obtain the unsaturated diester selectively. The latter compound is particularly important, since it can be easily transformed after hydrolysis and hydrogenation into adipic acid [52-54], Selective alkoxy-alkoxycarbonylation of 1,3-dienes has also been achieved [55]. 

Petroleum-derived benzene is the source of the six carbon atoms of adipic acid, an industrial chemical used to make nylon. An alternative process has been developed that uses genetically engineered strains of the bacterium Escherichia coli to convert glucose, a renewable resource obtained from cornstarch, to ds,c/s-muconic acid. Subsequent hydrogenation gives adipic acid. This chapter is about reactions that involve addition to double bonds and begins with hydrogenation. 

Wacker oxidation of styrene has also been performed in [bmim][BF4] and [bmim][PF6], at 60 °C with H2O2 and PdCF as a catalyst [19]. This system gave yields of acetophenone as high as 92 % after 3 h. Hydrogen peroxide may also be used under phase transfer conditions for alkene bond cleavage, to produce adipic acid (an intermediate in the synthesis of nylon-6) from cyclohexene (Scheme 9.9). 

Similar structures have been found for many other dicarboxylic acids, including succinic acid, COOH(CH ) COOH glutaric acid, COOH(CH ) COOH adipic acid, COOH(CH,) pOOH, and sebacic aoid, COOH(CH )jCOOH. Crystal structure determinations have also been made of many carboxylic acid hydrates in all of the crystals the carboxyl groups form hydrogen bonds, usually with water mole oules. An example is oxalic acid dihydrate in this crystal the 0—H 0 distance is 2.50 A. 

Figure 14.7 Screenshots of a hypothetical CALB-catalyzed esterification with acylation of serine by adipic acid (steps a to c) and deacylation by 1,6-hexanediol (steps d to f). Yellow lines depict hydrogen bondings.

Oxidative cleavage of cycloalkenes is an important reaction, usually affording co,a/-dicarboxylic acids e.g., adipic acid is formed on oxidation of cyclo-hexene by permanganate.114 If there is no hydrogen on one of the doubly bonded carbon atoms, the product is an oxo carboxylic acid, e.g., a>pinonic acid from a-pinene 115... 

Complex with distinct discotic shapes can also be obtained by hydrogen bonds between different (complementary) molecules (Fig. 5.1b). For example, supramolecular chiral LC assemblies can be obtained by hydrogen bonding clipping association (Fig. 5.9) [65]. 3-Methyl adipic acid (MeAdip) acting as a chiral clip is... 

Fig. 5.9 Chemical structiues of 45a, b and their supiamolecular chiral columnar structures formed with a chiral adipic acid by hydrogen bonding clipping association. Repinted with the permission from Ref [65], Copyright 2005, American Chemical Society...

The repeating unit in nylon 66 is the combination of adipic acid and hexamethylenediamine, both of which consist of six carbon atoms. Hence, the qualification 66. In each step as two molecules are connected, one molecule of water is removed. This process is a typical condensation polymerization. Because an amide group on one polymer chain can hydrogen-bond to that of the adjacent polymer chain as in silk (see Fig. 5.4), nylon forms a structure similar to the p-pleated sheet. The formation of nylon 66 can readily be demonstrated as some of you might have seen (Fig. 5.6). As you see, you can combine any compounds as long as one has amine... 

In a very similar way a simple receptor for dicarboxylic acids can be constmcted from the reaction of 2-aminopicoline with terephthaloyl dichloride. Diamide 3 now possesses two bidentate binding regions at a distance apart that coresponds to the spacing of the carboxylic acid groups in adipic or glutaric acid. Thus 3 would be expected to bind to appropriately lengthed dicarboxylic acids via four hydrogen bonds as in 4. 

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