Pentachlorophenol, hydrogen-bond

Protonation becomes a rapid reaction in protic solvents and in the presence of acids, as demonstrated for, e.g., -butyl acrylate in aqueous solution [207], methyl acrylate in EtOH [208], cinnamates in the presence of phenol in DMF [209], and benzaldehyde in ethanolic buffer solution [210]. Rate constants for protonation of aromatic radical anions (anthracene [211], naphthalene, 2-methoxynaphthalene, 2,3-dimethoxynaphthalene) by a number of proton donors including phenols, acetic acid, and benzoic acids in aprotic DMF were found to vary from 5.0 X 10 M- s-> (for anthracene, in the presence of p-chlorophenol) to 6.2 x lO s (for anthracene, in the presence of pentachlorophenol) [212]. For dimedone, PhOH, or PhC02H the rate of protonation depends on the hydrogen-bond basicity of the solvent and increases in the order DMSO < DMF MeCN [213],... 

The simplest aromatic alcohol, phenol, has not been investigated by INS although the chloro derivative pentachlorophenol [53] has been studied. The molecule forms a number of unusually strongly hydrogen bonded complexes with substituted pyridines and this is undoubtedly the first step in the investigation of these complexes. 

An interesting case of polymorphism has been reported by Harbison and coworkers for the complex of pentachlorophenol with 4-methylpyridine (4MPPCP) [44]. The substitution of hydrogen with deuterium at the hydrogen-bonded position leads to an entirely different crystal polymorph (Fig. 3.2.17). In particular the... 

Steiner, T, Wilson, C.C. and Majerz, I. (2000) Neutron diffraction study of a very short O-H---N hydrogen bond crystalline adduct of 2-methylpyridine and pentachlorophenol. Chem. Commun., 1231-1232. 

Gramstad, T. (1962) Hydrogen bonding. III. Intermolecular hydrogen bond association between nitrogen compounds and methanol, phenol, a-naphthol, and pentachlorophenol. Acta Chem. Scand., 16, 807-819. 

Gramstad, T. (1963) Hydrogen bonding. VII. Hydrogen-bond association of phenol and pentachlorophenol with carbonyl compounds and ethers. Spectmchim. Acta, 19, 497-508. 

Methylpyridine—Pentachlorophenol revealed by NMR implications for the shapes of hydrogen—bonded protons in the solid and the liquid state. /. Phys. Chem. A, 116, 11370-11387. 

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