Benzoic acid derivatives, hydrogen bonding

Hydrogen bonded complex formed by three long-chain-substituted benzoic acid derivatives (54) [73] and a tris(imidazole) base (55) with a four-component supramolecular disk shape (543-55) (Fig. 5.14a) also exhibits columnar meso-phases. Interestingly, the 3 1 complex with the less symmetrical 3,4-substituted benzoic acid shows a more stable mesophase (Cr 72 M 244 I) than the derivative formed from the 3,4,5-substituted benzoic acid (Cr 63 M 214 I). A related system has also been reported which uses a benzotri(imidazole) (57) as the trifunctional core unit (Fig. 5.14b) along with benzoic acid derivatives (56) [74]. This 1 3 complex exhibits a hexagonal columnar mesophase between 23 and 75 °C. The acrylate moieties on the alkoxyl chains could be photopolymerized to covalently... 

Table 11 Molecular properties of some benzoic acid derivatives on a model carbon phase. FSl, VWl, HBl, and ESI represent the energy value of the final (optimized) structure, the van der Waals energy, the hydrogen-bonding energy, and the electrostatic energy (kcal mol ) of the complexes between a model carbon phase and a benzoic acid derivative. Log 2 values from ref. 11, log represents the capacity ratios of the molecular form, log 2i represent the ionized form, values from ref. 12. Reproduced by permission of Elsevier, ref. 15.

Table 13 Molecular properties of some ionized benzoic acid derivatives, fsi, hbi, esi, and vwi are final structure, hydrogen bonding, electrostatic, and van der Waals energy values of ionized benzoic acid derivatives. FSi, HBi, ESi, and VWi are energy values of complexes of ionized benzoic acid derivatives and a pentyl-bonded silica gel (kcal mP ). Reproduced by permission of Elsevier, ref. 15.

Maspoch D, Catala L, Gerbier P, Ruiz-Molina D, Vidal-Gancedo J, Wurst K, Rovira C, Veciana J (2002) Radical para-benzoic acid derivatives transmission of ferromagnetic interactions through hydrogen bonds at long distances. Chem Eur J 8 3635-3645... 

Sharif, S., Powell, D.R., Schagen, D., Steiner, T.M., Toney, M.D., Fogle, E., and Limbach, H.H. (2008) X-ray crystallographic structures of enamine and amine Schiff bases of pyridoxal and its 1 1 hydrogen bonded complexes with benzoic acid derivatives evidence for... 

We now turn to substituent-sensitive tautomerism. Johnson and Rumon studied a series of solids derived by cocrystallizing substituted benzoic acids and substituted pyridines (108). Their IR evidence indicated, as expected, that when the benzoic acid is a strong acid and the pyridine a strong base, salts 50a are formed. For a weak acid and a weak base, hydrogen-bonded pairs of neutral molecules,... 

Fig. 9 H/D isotope effects on the hydrogen bond geometries H/D isotope effects, A5 = 8Hd - SHh. for the encapsulated benzoic acid (BA) derivatives (d12 mesitylene, open circles) and non-encapsulated (CDF3/ CDF2C1 filled circles) dimers of carboxylic acids as a function of the bridging proton chemical shift 8Hh...

Arylpyrroles, substituted or unsubstituted at the nitrogen, undergo a much more drastic oxidation than alkyl derivatives by the action of hydrogen peroxide. In most cases opening of the heterocyclic ring occurs, both at the bond between the heteroatom and the a-carbon and between the a- and )8-carbon atoms. From 2,5-diphenylpyrrole in acetic medium benzoic acid and acetophenone are formed.51 From 2,3,5-triphenyl-pyrrole (58, R = H) the product is 59,61 while from 58 (R = benzyl) the compounds 60 (R = benzyl) and 61 are produced.62 Other pyrroles that were found to behave similarly are listed below. 

Utilization of the single hydrogen bond between pyridine and benzoic acids in SLCP s has been a source of inspiration for other groups in the development of main-chain supramolecular polymers based on diacids and dipyridines.53-56 Supramolecular rod-coil polymers have been developed by assembly of 4,4 -bipyridines and telechelic polypropylene oxide with benzoic acid end-groups, which show highly ordered liquid crystalline phases.57 The use of tartaric acid derivatives in combination with bipyridine units resulted in the formation of hydrogen-bonded, chiral main-chain LCP s, as has been shown by circular dichroism measurements, optical microscopy, and X-ray data.58,59... 

Krygowski, T.M. and Wieckowski, T. (1981) Analysis of the hydrogen-bridge in carboxylic acids in terms of stabilization energy derived from bond lengths. Non-Hammett properties of p-substituted benzoic acids in the crystalline state. Croat. Chem. Acta, 54, 193-202. 

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