Potassium phenate

Manufacture. Several methods have been described for the preparation of -hydroxyben2oic acid. The commercial technique is similar to that of salicylic acid, ie, Kolbe-Schmitt carboxylation of phenol. The modification includes the use of potassium hydroxide in place of caustic (51). The dried potassium phenate is heated under pressure, 270 kPa (2.7 atm) or more, with dry carbon dioxide at 180—250°C. The potassium salt [16782-08-4] of Nhydroxyben2oic acid forms almost quantitatively and can be converted to free acid by using a mineral acid. 

In contrast to this low yield reaction, condensation of potassium 2-bromo-4-chlorophenate under Ullmann conditions gave 2,7-dichlorodibenzo-p-dioxin in 74% yield (8). The preferential displacement of bromine follows the pattern Weingarten observed in the reaction between potassium phenate and bromobenzene (9, 10). 

Monomers 111 (a -d), were prepared from the common starting material 15 by a potassium phenate displacement of the aromatic nitro group. The yields of the keto-ether amine products ranged from 90 to 100% and were of sufficient purity after extractive work up to be utilized directly in the synthesis of the various maleimide monomers. Imidization of the aminobenzocyclobutenes was accomplished using standard reaction conditions (maleic anhydride to form the amic acid followed by cyclodehydration with acetic anhydride and triethyla-mine) and provided the maleimide products in yields ranging from 60 to 90%. 

Mechanisms for the carboxylation of sodium phenate and potassium phenate (Figs. 2, 3) are given below. 

As far as potassium is concerned, bipotassium salicylate is not thermally stable and restructures itself intermolecularly to form tri-potassium isophthalate and potassium phenate. 

The carboxylation of potassium phenate gives excellent selectivity in producing parahydroxybenzoic acid. 

Table 3. The influence of temperature carboxylation of potassium phenate... 

Hyttroxyisopbtbalic Acid. 4-Hydroxy-l,3-benz-enedicarboxylic acid. C,H405 mol wt 182.13. C 52,75%, H 3.32%, O 43.92%. Prepd by high pressure carbonation of potassium phenate (Kolbe -Schmitt reaction) Baine et aL. J. Org. Chem. 19, 510 (1954) or by boiling salicylic acid with carbon tetrachloride in alkaline medium in the presence of Cu powder Ger. pat. 258,887 (1913 to Zeltner. Landau) Chem. Zentr. 1913,1, 1641 Frdl. 11, 210. Major constituent of the brown dust residue from sublimation of salicylic acid Hunt et aL, Chem. Ind. (London) 1985, 417. 

Fhenates.—Carbolates.—The hydrogen of the oxhydryl group-of phenol is replaceable by certain metals and by alcoholic radicals to form phenates. When phenol and KHO are heated together, potassium phenate, CeHsiOK, is formed. This, when treated in alcoholic solution with HgCh, produces mercuric phe-nate, (C H60,)jHg, a yellow, crystalline solid which has been used in medicine. 

The phenylic ethers may be obtained by heating potassium phenate with the iodid of the alcoholic radical. 

Potassium phenate. See Potassium phenoxide Potassium phenoxide CAS 100-67-4 EINECS/ELINCS 202-877-7 Synonyms Phenol, potassium salt Potassium phenate... 

The reaction generates easily oxidizable alkali phenates. Thus, the polymerization must be conducted in an inert atmosphere. The sodium and potassium salts of the bisphenols are widely used because they are more soluble in polar aprotic solvents. 

To investigate the possibility of preparing uniquely substituted hexa-chlorodibenzo-p-dioxins, several experiments were performed under Ullmann conditions. Although condensation of potassium 2-bromo-4-chlorphenate occurred readily, several 2,6-substituted phenates failed to... 

Offered as a solution containing 47% potassium trichlorophenate and 3% other potassium chloro-phenates, d 1.3, fp -9C. 

With large cations (soft) K+, Rb+, Cs+, this bisalt is not thermally stable and parahydroxybenzoic acid is formed via isophtalate to phenate. This mechanism is possible with potassium and is favoured at low C02 pressures ( 1 bar) and at high temperatures (> 180 ° C). 

TYPE OF POLYMERIZATION Nucleophilic displacement of activated aromatic halides in polar solvents by cilkali metal phenates or Friedel-Crafts processes examples include polycondensation of the potassium salt of hydroquinone and 4,4 -difluorobenzophenone in DMSO at temperatures up to 340°C and the polycondensation of 4,4 -difluorobenzophenone and silylated hydroquinone at 220-320°C. 

---