Hydrogen bonds with participation

Afonin, A.V., A.V. Vashchenko, LA. Ushakov et al. 2008. Comparative analysis of hydrogen bonding with participation of the nitrogen, oxygen and sulfur atoms in the 2(2 -heteroaryl)pyrroles and their trifluoroacetyl derivatives based on the H, C, N spectroscopy and DFT calculations. Magn Reson Chem 46 (5) 441 47. 

Esters can participate m hydrogen bonds with substances that contain hydroxyl groups (water alcohols carboxylic acids) This confers some measure of water solubil ity on low molecular weight esters methyl acetate for example dissolves m water to the extent of 33 g/100 mL Water solubility decreases as the carbon content of the ester increases Fats and oils the glycerol esters of long chain carboxylic acids are practically insoluble m water... 

Acyl-, 4-alkoxycarbonyl- and 4-phenylazo-pyrazolin-5-ones present the possibility of a fourth tautomer with an exocyclic double bond and a chelated structure. The molecular structure of (138) has been determined by X-ray crystallography (Table 5). It was shown that the hydroxy group participates in an intramolecular hydrogen bond with the carbonyl oxygen atom of the ethoxycarbonyl group at position 4 (8OCSCII21). On the other hand, the fourth isomer is the most stable in 4-phenylazopyrazolones (139), a chelated phenyl-hydrazone structure. 

The X-ray structure of the FBPase-AMP complex (Figure 2) revealed unfilled space near Nl, C2 and N3. Since the residues in the vicinity were hydrophobic and neither Nl nor N3 participated in a hydrogen bond with the protein, analogs, 2-S-methyl AMP (7), 2-methyl AMP (8), 2-ethyl AMP (9) and 2-chloro AMP (10) (Figure 5) were evaluated to determine whether these substituents gained favorable hydrophobic interactions with Met 188. 

Fig. 4.18 The different degree to which electrons move collectively in various forms of carbon material as evidenced by distinct intensity of the plasmon peak located about 6 eV in EELS spectra (arrow). Hydrogen atoms can make less strong covalent bonds with participation of n electrons if the interplanar distance is increased in layered graphitic nanocrystals as seen in carbon nanosheUs (frame in Fig. 4.17) and in disordered graphitic carbons (Sect. 4.3.1). After [60]...

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