Potassium phenolate, alkylation with

Cyanide and thiocyanate anions in aqueous solution can be determined as cyanogen bromide after reaction with bromine [686]. The thiocyanate anion can be quantitatively determined in the presence of cyanide by adding an excess of formaldehyde solution to the sample, which converts the cyanide ion to the unreactive cyanohydrin. The detection limits for the cyanide and thiocyanate anions were less than 0.01 ppm with an electron-capture detector. Iodine in acid solution reacts with acetone to form monoiodoacetone, which can be detected at high sensitivity with an electron-capture detector [687]. The reaction is specific for iodine, iodide being determined after oxidation with iodate. The nitrate anion can be determined in aqueous solution after conversion to nitrobenzene by reaction with benzene in the presence of sulfuric acid [688,689]. The detection limit for the nitrate anion was less than 0.1 ppm. The nitrite anion can be determined after oxidation to nitrate with potassium permanganate. Nitrite can be determined directly by alkylation with an alkaline solution of pentafluorobenzyl bromide [690]. The yield of derivative was about 80t.with a detection limit of 0.46 ng in 0.1 ml of aqueous sample. Pentafluorobenzyl p-toluenesulfonate has been used to derivatize carboxylate and phenolate anions and to simultaneously derivatize bromide, iodide, cyanide, thiocyanate, nitrite, nitrate and sulfide in a two-phase system using tetrapentylammonium cWoride as a phase transfer catalyst [691]. Detection limits wer Hi the ppm range. 

The extent of C-alkylation as a side reaction in etherification varies about 1% of allyl 2-allylphenyl ether is formed when phenol is used in the acetone and potassium carbonate method with allyl bromide with cinnamyl bromide or 7,7-dimethylallyl bromide the extent of C-alkylar tion is greater.16 A complicated mixture of C- and O-alkylation products results from the treatment of phenol with 4-bromo-2-hexene and 4-chloro-2-hexene. 9 4-Hexenylresordnol has been obtained in about 40% yield from the reaction of l-bromo-2-hexene, resorcinol, and potassium carbonate in boiling acetone.99 An appreciable amount of C-alkylation occurs when 2,6-dimethyIphenol is treated with allyl bromide and sodium ethoxide in ethanol.70 Since, in general, the ampunt of C-alkylation is greatly increased by carrying out the alkylation on the sodium salt of the phenol in benzene,16 this method is unsuitable for the preparar tion of allyl aryl ethers. 

The dianion (307), easily prepared from phenols and carbon disulfide in the presence of potassium hydroxide in DMSO, can be alkylated with 1,2-dibromoethane to form the 1,3-dithiole derivatives (308) (65LA(684)37). 

The effect of both podands and coronands on the Sn2 alkylation of potassium phenolate with 1-bromobutane in 1,4-dioxane s = 2.2) has been investigated by Ugel-... 

Syntheses of alkyl phenyl ethers, C,H, OR, are carried out by refluxing aqueous or alcoholic solutions of alkali phenolates with alkyl halides the yields vary with the nature of the alkyl halides (40-80%). The reactive halogen in benzyl halides is easily replaced by an alkoxyl group (95%). ° The choice of a solvent is sometimes important. Thus, in the preparation of the alkyl ethers of o- and p-hydroxybiphenyl from a mixttire of the phenol, alkyl halide, and powdered potassium hydroxide, high yields are obtained using acetone as a solvent, whereas, with alcohol as solvent, only small yields are obtained. Triarylmethyl chlorides react with alcohols directly (97%). ... 

Phenol readily couples with diazonium salts to yield coloured compounds. The latter can be nsed for the photometric detection of phenol as in the case of diazotized 4-nitroaniline. Sahcylic acid (2-hydroxybenzoic acid) can be prodnced by the Kolbe-Schmitt reaction (stndied by the density functional method ) from sodinm phenolate and carbon dioxide, whereas potassium phenolate gives the para compound. Alkylation and acylation of phenol can be carried out with aluminium chloride as catalyst methyl groups can also be introduced by the Mannich reaction. Diaryl ethers can only be produced under extreme conditions. 

Phenol reacts with hnear and branched alkenes in the presence of trill uoromethane-sulfonic acid (CF3SO3H) in chloroform to give the ortho- and para-aUcylphenols, in moderate yields (equation 8) °. With branched alkenes, the para-alkyl phenols are the major products. The regioselectivity is dramatically altered from entirely para-alkylphenol to ortlio-alkylphenol going from 100% potassium phenolate to 0% potassium phenolate in the presence of the Lewis acid AICI3. 

Aryl monothiolcarbonates have been obtained in 60% yield from a potassium phenolate in dioxan/dimethyl sulphoxide and carbon oxysulphide during 3 hours at ambient temperature foliowed by alkylation with a primary halide (PrI) as shown (ref.23). 

Aryl alkyl ethers. The reaction of an alcohol with hexamethylphosphorous triamide in carbon tetrachloride at low temperatures results in formation of an alkoxytris(dimethylamino)phoq>honium chloride (1), which can be converted into the stable hexafluorophosphate (2) by addition of ammonium hexafluoro-phospbate. The salt (2) reacts with potassium phenolates or aryl thiophenolates... 

Synthesis started with the reaction of commercially available 2-methoxy-4-nitroaniline, 1, with potassium hydroxide in aqueous dimethylsulfoxide to yield a phenol (2). The phenol was alkylated with dibromotetrafluoroethane following the general route described by Rico and Waskselman to give 2 (8). The addition of a catalytic amount of propanethiol is required for this reaction to proceed since it assists in the in-situ generation of tetrafluoroethylene, the electrophile in the reaction. 

Mercaptan extraction is used to reduce the total sulfur content of the fuel. When potassium isobutyrate and sodium cresylate are added to caustic soda, the solubility of the higher mercaptans is increased and they can be extracted from the oil. To remove traces of hydrogen sulfide and alkyl phenols, the oil is pretreated with caustic soda in a packed column or other mixing device. The mixture is allowed to settle and the product water washed before storage. 

Besides N-alkylation reactions, there are also reports in the literature concerning microwave-promoted O-alkylations. A mild method for the O-alkylation of phenols with alkyl bromides and chlorides has been developed by Wagner and coworkers (Scheme 6.117 a) [235], The protocol is applicable to substrates that are sensitive to strong bases or to hydrolysis, or are difficult to extract from an aqueous phase. The procedure uses methanol as a solvent and a stoichiometric amount of potassium carbonate as a weak base. Optimum yields were obtained by heating the phenol with 1.2 equivalents of the alkyl bromide (or 3 equivalents of the less reactive chloride) at 100-140 °C for 15-30 min. 

The ability of quaternary ammonium halides to form weakly H-bonded complex ion-pairs with acids is well established, as illustrated by the stability of quaternary ammonium hydrogen difluoride and dihydrogen trifluorides [e.g. 60] and the extractability of halogen acids [61]. It has also been shown that weaker acids, such as hypochlorous acid, carboxylic acids, phenols, alcohols and hydrogen peroxide [61-64] also form complex ion-pairs. Such ion-pairs can often be beneficial in phase-transfer reactions, but the lipophilic nature of H-bonded complex ion-pairs with oxy acids, e.g. [Q+X HOAr] or [Q+X HO.CO.R], inhibits O-alkylation reactions necessitating the maintenance of the aqueous phase at pH > 7.0 with sodium or potassium carbonate to ensure effective formation of ethers or esterification [49,64]. 

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