Carbonic acid, dipotassium salt

Potassium carbonate Carbonic acid, dipotassium salt (8, 9) (584-08-7)... 

SYNS CARBONIC ACID, DIPOTASSIUM SALT KALIUMCARBONAT (GERMAN) K-GRAN PEARL ASH POTASH... 

Carbonate of potash Carbonic acid, dipotassium salt Caswell No. 685 CCRIS 7320 Dipotassium carbonate EINECS 209-529-3 EPA... 

Carbonic acid dipotassium salt. See Potassium carbonate... 

Synonyms American ash Carbonate of potash Carbonic acid dipotassium salt Dipotassium carbonate Pearl ash... 

Potassium carbonate see carbonic acid, dipotassium salt... 

The electron-deficient nature of the s-tetrazine ring-carbons is indicated by formation of a dipotassium salt (C2N4K2) of tetrazine in liquid ammonia, by easy decarboxylation of the 3,6-dicarboxylic acid (335), and by the very weak basicity of the 3,6-diamine (336). 

Being formally a derivative of carbonic acid, 4,5-bis(ethylenedithio)-l,3-dithiol-2-one 188 is opened into the dipotassium salt 192 by the action of potassium ethoxide in THF (Equation 20) <1974JOC511>. 

Other reported syntheses include the Reimer-Tiemann reaction, in which carbon tetrachloride is condensed with phenol in the presence of potassium hydroxide. A mixture of the ortho- and para-isomers is obtained the para-isomer predominates. -Hydroxybenzoic acid can be synthesized from phenol, carbon monoxide, and an alkali carbonate (52). It can also be obtained by heating alkali salts of -cresol at high temperatures (260—270°C) over metallic oxides, eg, lead dioxide, manganese dioxide, iron oxide, or copper oxide, or with mixed alkali and a copper catalyst (53). Heating potassium salicylate at 240°C for 1—1.5 h results in a 70—80% yield of -hydroxybenzoic acid (54). When the dipotassium salt of salicylic acid is heated in an atmosphere of carbon dioxide, an almost complete conversion to -hydroxybenzoic acid results. They>-aminobenzoic acid can be converted to the diazo acid with nitrous acid followed by hydrolysis. Finally, the sulfo- and halogenobenzoic acids can be fused with alkali. 

In the Henkel process Henkel I-process), which was used on a large scale particularly in Japan until the late 1970 s, phthalic anhydride was converted into the dipotassium salt of phthalic acid, which isomerized to dipotassium terephthalate under a pressure of carbon dioxide of 10 to 50 bar at 350 to 400 °C. 

Henkel Rearrangement of Benzoic Acid and Phthalic Anhydride. Henkel technology is based on the conversion of benzenecarboxyhc acids to their potassium salts. The salts are rearranged in the presence of carbon dioxide and a catalyst such as cadmium or zinc oxide to form dipotassium terephthalate, which is converted to terephthahc acid (59—61). Henkel technology is obsolete and is no longer practiced, but it was once commercialized by Teijin Hercules Chemical Co. and Kawasaki Kasei Chemicals Ltd. Both processes foUowed a route starting with oxidation of napthalene to phthahc anhydride. In the Teijin process, the phthaHc anhydride was converted sequentially to monopotassium and then dipotassium o-phthalate by aqueous recycle of monopotassium and dipotassium terephthalate (62). The dipotassium o-phthalate was recovered and isomerized in carbon dioxide at a pressure of 1000—5000 kPa ( 10 50 atm) and at 350—450°C. The product dipotassium terephthalate was dissolved in water and recycled as noted above. Production of monopotassium o-phthalate released terephthahc acid, which was filtered, dried, and stored (63,64). 

A solution of 66.5 g. (1.01 moles) of 85% potassium hydroxide in 300 ml. of water in an 800-ml. beaker is heated to 60-70 , and 100 g. (0.505 mole) of commercial 1,8-naphthalic anhydride (Note 1) is stirred in. The pH of the resultant deep-brown solution is adjusted to a value of 7 (Note 2) with 6N hydrochloric acid and 3N potassium hydroxide. It is treated with 10 g. of decolorizing carbon and filtered. This operation is repeated. The filtrate is concentrated in a 1.5-1. beaker on a steam bath to about 180 ml. The concentrate is cooled to room temperature, 800 ml. of methanol is added with vigorous stirring by hand, and the mixture is cooled to 0-5°. The precipitated dipotassium naphthalate is separated by filtration, washed with 150 ml. of methanol, and dried in a vacuum oven at 150°/150 mm. The dried cream-colorcd salt weighs 130 135 g. (88 92%). 

Anhydrous dipotassium hydrophosphate, K2HPO4, could not be obtained by T. Graham in the solid crystalline condition L. Staudenmaier always obtained a more acid phosphate by crystallization from soln. containing eq. quantities of potassium hydroxide or carbonate and phosphoric acid. No hydrated form has been prepared. E. G. Parker, and J. d Ans and O. Schreiner have studied the conditions under which potassium and sodium salts are formed as solid phases— vide Figs. 86 and 87. E. von Berg prepared dirubidium hydrophosphate,... 

Synthesis. Benzenehexol is available only from laboratory reagent suppliers. The simplest laboratory preparation involves the aeration of the glyoxal—bisulfite addition product in sodium carbonate solution at 40—80°C, isolation of the sodium salt of tetrahydroxybenzoquinone, followed by acidification to obtain the free tetrahydroxy-p-benzoquinone in about 8% yield the latter is reduced with stannous chloride in boiling dilute hydrochloric acid solution to benzenehexol (77) in 77% yield (261). A similar procedure affords dipotassium rhodizonate (80) in good yield (262). 

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