Hydrogencarbonates, reactions

Group II hydrogencarbonates have insufficient thermal stability for them to be isolated as solids. However, in areas where natural deposits of calcium and magnesium carbonates are found a reaction between the carbonate, water and carbon dioxide occurs ... 

When heated, sodium hydrogencarbonate readily decomposes evolving carbon dioxide, a reaction which leads to its use as baking powder when the carhon dioxide evolved aerates the dough. In the soda-ammonia process the carbon dioxide evolved is used to supplement the main carbon dioxide supply obtained by heating calcium carbonate ... 

This reaction is used as a test for carbon dioxide. Passage of an excess of carbon dioxide produces the soluble hydrogencarbonate ... 

The hydrogencarbonate ion, produced in nature by this reaction, is one of the main causes of temporary hardness in water. Carbon dioxide is fairly soluble in water, 1 cm dissolving 1.7 cm of the gas at stp. The variation of solubility with pressure does not obey Henry s law, since the reaction... 

If the hydrogencarbonate is in solution and the cation is Ca or Mg. the insoluble carbonate is precipitated this reaction may be used, therefore, to remove hardness in water by precipitation of Ca or Mg ions.) The ease of decomposition of hydrogencar-bonates affords a test to distinguish between a hydrogencarbonate and a carbonate carbon dioxide is evolved by a hydrogencarbonate, but not by a carbonate, if it is heated, either as the solid or in solution, on a boiling water bath. 

Titration of carbonate ion with a strong acid. A solution of sodium carbonate may be titrated to the hydrogencarbonate stage (i.e. with one mole of hydrogen ions), when the net reaction is ... 

This reaction is subject to a number of errors (1) the hydriodic acid (from excess of iodide and acid) is readily oxidised by air, especially in the presence of chromium(III) salts, and (2) it is not instantaneous. It is accordingly best to pass a current of carbon dioxide through the reaction flask before and during the titration (a more convenient but less efficient method is to add some solid sodium hydrogencarbonate to the acid solution, and to keep the flask covered as much as possible), and to allow 5 minutes for its completion. 

There was also a Cannizzaro reaction that gives rise to an accident. During a reaction that was carried out by using furfural this compound came into contact with sodium hydrogencarbonate that is used to check pHs. This compound catalysed a Cannizzaro reaction that couid not be controlied and caused the compounds to combust ... 

There was an attempt to neutralise formic acid by using magnesium hydrogencarbonate. By stirring the medium without care, a violent reaction of the acid with carbonate took place. Carbon dioxide was released in large quantities and caused the projection of the compounds into the surrounding area. 

Following a published procedure [1], perchloric acid was used as catalyst in preparing a diol ketal, and was neutralised with sodium hydrogencarbonate before workup. Some sodium perchlorate remained dissolved after filtering the reaction mixture, and dining subsequent vacuum distillation (with the bath temperature increasing to 200°C) an explosion occurred. 

The reaction mixture was transferred into a separating funnel. The aqueous layer was extracted with dichloromethane (10 mL). The combined organic layers were washed with a aqueous solution of sodium hydrogencarbonate (2 x 20 mL), then with water (30 mL), dried over magnesium sulfate, filtered and the solvent removed under reduced pressure. 

In the industrial process [12] 1,3-butadiene and water are reacted at 60-80 °C in an aqueous sulfolane solvent in the presence of triethylamine hydrogencarbonate under 10-20 bar CO2 pressure. The reaction yields linear telomers mainly, with a 90-93 % selectivity to 2,7-octadien-l-ol together with 4-5 % l,7-octadien-3-ol. Most of the products are removed from the reaction mixture by extraction with hexane, and the aqueous sulfolane phase with the rest of the products, the catalyst and the ammonium bicarbonate is... 

A similar approach, involving condensation of 4-nitro-2-butanol with sodium glyoxylate309 in the presence of sodium hydrogencarbon-ate offers a route to 3-amino-3,4,6-trideoxy-DL-hexopyranoses. Two lactones, 552 and 553, were formed during the reaction (overall yield, 42%) in the ratio of 3 1 these lactones may be considered to be potential precursors of a variety of isomeric 3-amino sugars. The synthesis... 

The thioimidoester (60.0g, 319mmol), triphenylphosphine (334g, 1.28 mol) and anhydrous xylene (550 ml) were combined in a flame-dried 1000 ml three-necked flask. A solution of potassium t-butoxide (3.57 g, 32.0 mmol) in t-butyl alcohol (20 ml) was added dropwise and the reaction mixture was stirred at room temperature for 4h and then refluxed for 60 h. It was cooled and extracted three times with 10% HC1 (3X 150 ml). The combined aqueous extracts were washed three times with ether (3 X 50 ml), neutralized with solid sodium hydrogencarbonate and extracted with four portions of dichloromethane (4 X 100 ml). The combined dichloromethane layers were washed twice with brine (2 X 80 ml), dried over MgS04 and concentrated to give a crude brown solid which was sublimed (40°C/0.1 torr) to yield (1) (37.6 g, 76%), m.p. 62-63°C. 

An alternative procedure for the protection of L-sorbose (25), followed by oxidation at C-l and cyclization of the product to L-ascorbic acid, was developed by Hinkley and Hoinowski.257 L-Sorbose (25) was converted into methyl a-L-sorbopyranoside (37) by treatment with methanol and hydrogen chloride.258 Glycoside 37 was then oxidized with air in the presence of a suspension of platinum oxide in aqueous sodium hydrogencarbonate solution at 60°, to afford methyl ot-L-xylo-2-hexulopyranosidonic acid (38), which, when heated in hydrochloric acid, was converted into L-ascorbic acid (1), presumably by way of L-xy/o-2-hexulosonic acid (see Scheme 5). Acid 38 has also been prepared by oxidation of 37 with nitrogen tetraoxide.259,280 Yields were not reported for this reaction sequence, and it appears to offer no potential... 

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