Phenols Other methods

Other Methods. A variety of other methods have been studied, including phenol hydroxylation by N2O with HZSM-5 as catalyst (69), selective access to resorcinol from 5-methyloxohexanoate in the presence of Pd/C (70), cyclotrimerization of carbon monoxide and ethylene to form hydroquinone in the presence of rhodium catalysts (71), the electrochemical oxidation of benzene to hydroquinone and -benzoquinone (72), the air oxidation of phenol to catechol in the presence of a stoichiometric CuCl and Cu(0) catalyst (73), and the isomerization of dihydroxybenzenes on HZSM-5 catalysts (74). 

Ozone can be used to completely oxidize low concentrations of organics in aqueous streams or partially degrade compounds that are refractory or difficult to treat by other methods. Compounds that can be treated with ozone include alkanes, alcohols, ketones, aldehydes, phenols, benzene and its derivatives, and cyanide. Ozone readHy oxidizes cyanide to cyanate, however, further oxidation of the cyanate by ozone proceeds rather slowly and may require other oxidation treatment like alkaline chlorination to complete the degradation process. 

The large pore structure of the TSK-GEL G6000PW allows it to separate large molecules such as pBR322 plasmid from contaminating RNAs and proteins in a much shorter time frame than other methods (23). A two column system of G6000PW (7.5 mm i.d. X 60 cm) was used to separate the cleared lysate and phenol extract of the plasmid as shown in Fig. 4.34 (page 130). The plasmid... 

Sc(OTf)3, AcOH, p-nitrobenzoic anhydride or Sc(OTf)3, AC2O, 66- >95% yield. The lower yields are obtained with allylic alcohols propargylic alcohols give higher yields. Phenols are effectively acylated with this catalyst, but at a much slower rate than simple aliphatic alco-hols. The method was shown to be superior to most other methods for macrolactonization with minimum diolide formation. 

Mor alpha-) Dinitrophenol- Yel orthorhombic crysts from w, leaflets from ale mp 112—14° bp (decomp) d 1.683g/cc at 24°, 1.4829 at 72.5/4°. Sublimes when carefully heated volatile with steam. Can be prepd by the nitration of phenol, but this method is not considered commercially practicable because of partial decompn of the phenolic ring. A better method is by hydrolysis under pressure of 2,4-dinitrochloro-benzene, which in turn can be obtained by nitrating chlorobenzene. Other methods are given in Ref 1... 

In Table I, one notices also that phenol is electro-oxidatively polymerized, which does not occur by the other methods. 

Even the mildest pulping process, hydrotropic extraction, i.e. repeated extraction with concentrated aqueous solutions of organo-philic electrolytes such as sodium xylenesulfonate or cymenesulfonate, has failed because of an outlet for the extracted lignin, wliich is precipitated by mere dilution of the solution. Other methods based on hydrolysis of the wood with acids, e.g. HCl, HNO3, AICI3, acetic acid, acetyl chloride, SOg, or phenol, are merely of laboratory interest. 

Besides a variety of other methods, phenols can be prepared by metal-catalyzed oxidation of aromatic compounds with hydrogen peroxide. Often, however, the selectivity of this reaction is rather poor since phenol is more reactive toward oxidation than benzene itself, and substantial overoxidation occurs. In 1990/91 Kumar and coworkers reported on the hydroxylation of some aromatic compounds using titanium silicate TS-2 as catalyst and hydrogen peroxide as oxygen donor (equation 72) . Conversions ranged from 54% to 81% with substituted aromatic compounds being mainly transformed into the ortho-and para-products. With benzene as substrate, phenol as the monohydroxylated product... 

K. Ishihara, M. Kubota, H. Kurihara, H. Yamamoto, Journal of Organic Chemistry 1996, 61, 4560 Alcohols react preferentially over phenols an observation not common to other methods. 

TrinitTO 4-acetamidophenol, CHaCO.-NH. CeHfNOj),. OH, It brn scales (from AcOH), mp I9l-2ctdec), easily sol in ale AcOH, Can be prepd by treating 3,5-dit itro-4-acetamido-phenol with fuming nitric acid at0°or by other methods. Its explosive props were not examined Refs l)Beil 13,(195) 2)F. Reverdin ... 

F. Reverdin et al Ber 37, 4452(1905) 38, 1598(1906) 39, 126(1907) 3/5 Dinltro-4 amfnophenol or 4-Amfno-3,5-dinitro-phenol. Red ndls with greenish luster subl ca 150° and melts at 230 231 easily sol in ale and hot w, si sol in benz and nearly in sol in ligroin. Can be prepd by heating 3,5 dinitro-4-( 3-nitro-4-methyl benzene-sulfamino)-phenetoLe with coned Ha S04 on water bath (Ref 2) or by other methods (Refs 1 3)... 

The colorimetric method based on the reagents of Folin and Denis or of Folin and Ciocalteu has been generally preferred over other methods to determine total phenols in complex natural materials such as wines and fruits (1, 2, 3, 4, 5). This method is relatively simple, convenient, reliable, generally applicable, and it is accepted as an official analysis in several countries for total phenols in wines and a number of other products. Although it is a preferred method, it can be even better than is commonly recognized. 

It is pertinent at this point to refer briefly to the sources of quinone methides, though these have been reviewed (B-74M122400). The general approach used in chroman syntheses involves the thermal elimination of HX from an -substituted phenol. Commonly the eliminated molecules are water, methanol or dimethylamine (287 X = OH, OMe, NMe2, respectively). However, these methods are not entirely suitable because the eliminated molecules may promote side reactions. In the case of 1,2-naphthoquinone 1-methide, the thermal dissociation of the spirodimer (288) is a better source than the other methods. Its formation represents another example of dimerization by a [4+2]-cycloaddition, since it is prepared by heating l-dimethylaminomethyl-2-naphthol in dodecane or xylene with careful exclusion of moisture (73JCS(P1)120,81CJC2223). 

Other methods which have proved of value include the formation of substituted methides by the action of silver oxide on phenols (70JOC3666). It is postulated that upon oxidation of the phenol a phenoxy radical is formed which dimerizes to the quinol ether. Disproportionation to the methide and the original phenol follows. 

Note The presence of p nloroglucinoi can be detected by ferric chloride(blue coloration) or by other phenolic reaction methods... 

In other methods of metallizing dyes in the receiver, metal chelates are used in a polymeric matrix. Examples of ligands for the metal ion include diazabicyclo[2.2.2]octane,128 the 2,2 -bis-phenol (60)129 and the iminodiacetic acid (61).,3°... 

Regarding these uncertainties the agreement of phenol alcohols found in kraft lignin with FeCl3 test and other methods is very reassuring. This colorimetric method is less applicable for M.W.L. preparations in which only a small amount of phenol alcoholic groups can be formed. 

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