Oxygen in phenols

Figure 6. Comparison of yields of oxygen in pyrolytic water with estimated content of oxygen in phenolic hydroxyl groups in raw coal. (-)...

Correlation of percent oxygen in phenolic hydroxyl groups in coal, Given (28) (O) this study (7) (+) this study corrected for decomposition of kaolinite (A) Loison and Chauvin (22) ( ) Fitzgerald and Van Krevelen (23) (V) Jiintgen and Van Heek (24) after Hanbaba et al. (25). 

The phenyl group is joined to carbon in the hydroperoxide and to oxygen in phenol clearly, rearrangement takes place. This time, it involves a 1,2-shift to electron-deficient oxygen. 

Since o-bromine even further reduces the electron density on oxygen in phenols, this unusual effect of the bromine substitutuent may be more drastic in 7B. The fact that more than one equivalent of oxidant was needed for successful reaction supports the idea that either free-radical formation is very slow (thermodynamic control) or that polymerization is taking place by radical-radical rather than radical-anion (S T) coupling, thus consuming the free radicals.46... 

When the lone-pair electrons of oxygen in phenol conjugate with the ring, there is charge separation ... 

As Section 22-5 will show, the oxygen in phenol and its ethers is also weakly basic, in the case of ethers giving rise to acid-catalyzed cleavage. 

In Summary The oxygen in phenols and alkoxybenzenes can be protonated even though it is less basic than the oxygen in the alkanols and aUcoxyalkanes. Protonated phenols and their derivatives do not ionize to phenyl cations, but the ethers can be cleaved to phenols and haloalkanes by HX. Alkoxybenzenes are made by Williamson ether synthesis, aryl alkanoates by acylation. 

As we ve seen on a number of occasions bonds to sp hybridized carbon are shorter than those to sp hybridized carbon and the case of phenols is no exception The carbon-oxygen bond distance in phenol is slightly less than that in methanol... 

In resonance terms the shorter carbon-oxygen bond distance in phenol is attrib uted to the partial double bond character that results from conjugation of the unshared electron pair of oxygen with the aromatic ring... 

Many of the properties of phenols reflect the polarization implied by the resonance description The hydroxyl oxygen is less basic and the hydroxyl proton more acidic in phenols than m alcohols Electrophiles attack the aromatic ring of phenols much faster than they attack benzene indicating that the ring especially at the positions ortho and para to the hydroxyl group is relatively electron rich... 

Wada and coworkers have recently prepared a number of very similar systems in which the bridging chain is bonded to the benzo group by oxygen . The phenolic ox-... 

Hydrogenolysis, without ring reduction, of the carbon-oxygen bond in phenols cannot be depended on, but by conversion of the phenol to a better leaving group, such as is formed by interaction of the phenol with 2-chlorobenzoxazole, l-phenyl-5-chlorotetrazole, phenylisocyanate,... 

Sonnerskog [82] found that PVC could oxidize a number of phenols at room temperature in the absence of oxygen. In addition, a graft copolymer was formed when acrylonitrile was added to PVC. These results were taken as indications for the peroxy groups in PVC. 

Polyphenylene oxide (PPO) is produced by the condensation of 2,6-dimethylphenol. The reaction occurs by passing oxygen in the phenol solution in presence of CU2CI2 and pyridine ... 

In comparison to the normal reaction without additive which affords a yield of 50.2 % in phenol, the additives on the right part of the table reduce the induction time probably by trapping more or less efficiently the air-oxygen inhibitor. 

Pd(II) Wacker-type catalysts were also studied.146 Selective oxidation of benzene to phenol by molecular oxygen in the presence of Pd and heteropolyacids have been published.147... 

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