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Halogenophenols

FIGURE 13. The minimum energy structures of cis and trans meta- and para-XQHaOH (X = F, Cl and Br). Bond lengths are in A, bond angles in degrees. Adapted from Reference 220 with permission [Pg.58]

Furthermore, one obtains certain subtle features in the spectra of m-XCelLtOH whose origin can only be explained by the co-existence of two very slightly inequivalent con-formers of the cis and trans types. This is seen, for example, from the magnitude of cis-trans meta ranging from —0.8 kJmoL for F to -1-0.08 kJmol for Cl, and finally to -1-0.04 kJmoL for Br. If the difference is extremely small for Cl and Br, F is then an exception. Contrary to Cl and Br, we obtain that the trans conformer of m-FC6H40H is a little more stable than its cis conformer. The cis-trans differences in the geometrical [Pg.58]

TABLE 18. Harmonic vibrational frequencies, IR intensities and assignments forpara-fluorophenol  [Pg.65]

Fnrther, if in all para-snbstitnted phenols the CO stretching vibration is mainly localized on these two fnndamental modes, in some ortho- and meta-phenols it appears coupled with the mode corresponding to the fnndamental three of benzene whose displacements resemble a distortion towards a Catherine wheel type of strnctnre. Snch vibration appears to be rather sensitive to the position (i.e. either cis or tram) of the X atom, being almost independent of its natnre. In all tram ortho- and meto-snbstitnted phenols, it is placed at slightly lower wavennmbers and characterized by a consistently larger IR intensity compared to the cis conformers. Consider the following example. For all tram m-XCeHjOH, it is centred at ca 1322 cm (81-83 kmmoC ) and bine shifts to ca 1334 cm (2-7 kmmoG ) for the cis conformer. In tram ortto-snbstitnted forms, it is found at 1316-1317 cm (73-78 kmmoC ), while in the cis forms it is at 1323-1324 cm- (21-28 kmmor ). [Pg.67]


The reaction between copper(I) acetylides and o-halogenophenols or -anilines provides a general and convenient route to 2-substituted benzofurans or indoles (Scheme 71g) (66JOC4071). [Pg.129]

The first finding was that the four p-halogenophenols (X = F, Cl, Br, or 1) have remarkably similar transition state stabilization (XTS = 0.40, 0.43, 0.46, and 0.29 mM), even though these substrates have a wide range of ability to bind to a-CD (Ks = 120, 3.6, 1.4, and 0.47 mM) (Table A4.4). This finding is inconsistent with inclusion of the phenol by the CD during the catalysed bromination and so affords yet further support for the view of the transition state implied in [9] -> [10],... [Pg.21]

Heating o-alkynylphenols (36, X = 0), which are available from o-halogenophenols and alkynes, without or with palladium catalysts, yields benzofurans (37, X = 0). [Pg.610]

Environmental photosensitization processes may be stimulated not only by natural but also by anthropogenic pollutants, such as phenols and dihydroxyben-zenes, which are efficient photosensitizers. Among others, phenol was found to sensitize the dehalogenation of halogenophenols [99], This behaviour shows that the simultaneous presence of adequate sensitizer and quencher in polluted environment can lead to the photosensitized decomposition of the latter and thereby to abatement of the pollution. [Pg.150]

Alkylphenols, nitrophenols, halogenophenols and polyhydroxybenzenes have been extensively studied on a thin layer of anion and cation exchangers with cellulose, paraffin, and polystyrene matrices and on silanized silica gel impregnated with anionic and cationic surfactants. The best results have been obtained by using cation exchangers and anionic surfactants as impregnating agents [4,5]. [Pg.1193]

The work of Allan and Reeves (1962, 1963) illustrates the use of chemical shift measurements to obtain enthalpies of formation for both intra- and inter-molecular hydrogen bonds involving the same molecules. The measurements do not rely on infrared studies of the same systems but the thermodynamic results from the two techniques are in agreement. In orffeo-halogenophenols the equilibrium at finite concentrations in an inert solvent can be represented as two chemical equations... [Pg.260]

In the substituted phenol/napthol group, p-phenylphenol is an extremely potent enhancer, with a reported amplification factor of 530 under experimental conditions in which 6-hydroxybenzothiazole (at double the phenol concentration) had an amplification factor of only 27 (T7) Para-substituted halogenophenols are also... [Pg.120]

The reactions of halogenophenols are discussed in this section dealing with fiuoro, chloro, bromo and iodophenols. Certain of these reactions would of course take place in the absence of the halogen substituent and it is perhaps remarkable that many of the cydisations described occur despite the deactivating influence of that group. [Pg.237]

Omura, K. and T. Matsuura. 1971. Photolysis of halogenophenols in aqueous alkali and in aqueous cyanide. Tetrahedron 27, 3101-3109. [Pg.410]

An original aspect of aqueous otochemlstry related to the anticipated fact that water would favour photochemical processes implying polarized or ionic excited states, is en haslzed in the class of chlorobenzenes and halogenophenols. Such photoprocesses would be more specific than hemolytic photodissociation leading to radicals. [Pg.10]


See other pages where Halogenophenols is mentioned: [Pg.950]    [Pg.150]    [Pg.47]    [Pg.48]    [Pg.57]    [Pg.450]    [Pg.81]    [Pg.261]    [Pg.225]    [Pg.237]    [Pg.317]    [Pg.10]    [Pg.11]    [Pg.16]    [Pg.16]    [Pg.368]    [Pg.450]    [Pg.261]    [Pg.150]    [Pg.335]    [Pg.263]    [Pg.275]    [Pg.367]    [Pg.278]    [Pg.282]    [Pg.284]    [Pg.247]   


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O-Halogenophenols

O-Halogenophenols diazo oxides

O-Halogenophenols phenols

Phenols halogenophenols

Reactions of Halogenophenols

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