Hydrogen amide type

Biotin (5) is the coenzyme of the carboxylases. Like pyridoxal phosphate, it has an amide-type bond via the carboxyl group with a lysine residue of the carboxylase. This bond is catalyzed by a specific enzyme. Using ATP, biotin reacts with hydrogen carbonate (HCOa ) to form N-carboxybiotin. From this activated form, carbon dioxide (CO2) is then transferred to other molecules, into which a carboxyl group is introduced in this way. Examples of biotindependent reactions of this type include the formation of oxaloacetic acid from pyruvate (see p. 154) and the synthesis of malonyl-CoA from acetyl-CoA (see p. 162). 

In the presence of ammonia, the metal-azide unit can possibly undergo facile ammonolysis in the same way as alkyl-amide type precursors, but it produces HN3 instead of alkylamines. Hydrogen azide itself acts as a very efficient source for the N-component (see Eq. 5). In Ihe case of ammonolysis of metal azides in the gas phase, HN3 would be produced in situ only in the reactor close to the substrate surface, thus circumventing the intrinsic problems... 

Figure 29-5 Possible hydrogen-bonded structure for crystallites of nylon 66, an amide-type polymer of hexanedioic acid and 1,6-hexane-diamine...

Hydrogen bond types that are widely used in organic crystal engineering, primarily D-H A where D, A = O or N, will inevitably be important in inorganic systems since the same functional groups that form such hydrogen bonds, i.e. carboxyl, amide, oxime, alcohol, amine, etc., can be present as part of organic... 

The partial IR spectrum of acid Subfraction 1 shows IR absorption at 3460 cm because of the pyrrolic nitrogen N-H absorption of carba-zole-like compounds. Amide carbonyl absorption appears at 1685 cm" The partial IR spectrum of acid Subfraction 2 shows the same two IR bands and additional bands at 3585 cm and 1650 cm owing to phenols and a second amide type. The partial IR spectrum of acid Subfraction 3 shows phenol absorption at 3585 cm S pyrrolic nitrogen absorption at 3460 cm S and strong carbonyl absorption at 1695 cm and 1725 cm characteristic of carboxylic acid dimers and monomers. In addition, absorption of hydrogen-bonded carboxylic acid and phenolic hydroxyl groups can be seen in the region of 3500-2300 cm" ... 

The acceptor and donor strength of many functions besides fhose of fhe amide type have been characterized by the analysis of associations between simple molecules, such as, e.g., phenols and anilines, for which fhousands of experimental data exist, mosfly measured in chloroform or in carbon tetrachloride [94, 95]. Although these data are hampered by less well-defined structures compared to supramolecular complexes, they not only give a fairly consistent basis for the prediction of hydrogen-bonded associations but also can be used, e.g., for crown efher and cryptand complexes with alkali or ammonium ligands [32]. 

Fig. 2 Template syntheses of rotaxanes the Cu(I) ion binds a phenanthroline ligand inside a macrocycle (top left). A l f5-paraquat macrocycle is clipped around an axle bearing a hydroquinone center piece (top right). Hydrogen bonding permits the use of nonionic template effects for the preparation of amide-type rotaxanes (bottom left). Phenolate anions bound to the macrocycle react as a supramolecular nucleophile (bottom right).

To restore aromaticity, hydride ion is displaced. The hydride then attacks the amino group to give hydrogen gas and an amide-type anion (see eq. 11.17). 

Figure 10.1 Hansen solubility parameters of four amide-type solvents, two morpholine derivatives, and acetonitrile in terms of the polarity and hydrogen bonding values. The average values of the alcohol-type solvents, ester-type solvents, ether solvents, ketone solvents, and the average values for the E-series glycol ethers are included also.

Other groups containing active hydrogen atoms (such as amino and carboxyl groups) are also able to react with the isocyanate group but these lead to the formation of urea- and amide-type linkages. 

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