Potassium metal reactions with

Sir Humphry Davy attempted to isolate this unidentified element through electrolysis—but failed. It was not until 1824 that Jons Jakob Berzehus (1779—1848), who had earlier discovered cerium, osmium, and iridium, became the first person to separate the element silicon from its compound molecule and then identify it as a new element. Berzehus did this by a two-step process that basically involved heating potassium metal chips with a form of silica (SiF = silicon tetrafluoride) and then separating the resulting mixture of potassium fluoride and silica (SiF + 4K —> 4KF + Si). Today, commercial production of sihcon features a chemical reaction (reduction) between sand (SiO ) and carbon at temperatures over 2,200°C (SiO + 2C + heat— 2CO + Si). 

The direct introduction of an acetylide moiety, using pyridine A-oxide (or quinoline, diazine and triazine iV-oxides) can be achieved in a comparable way, by reaction with potassium phenylacetylide reaction with the lithium salt requires addition of acetyl chloride at the end of the reaction to aromatise. At low temperature, and using i-PrMgCl, 2-metallation of pyridine iV-oxides can be achieved, and thus, the introduction of electrophiles at the 2-position. ... 

BORIC ACID (10043-35-3) BH3O3 Aqueous boric acid is a weak acid incompatible with alkali carbonates hydroxides strong reducing agents, including metal hydrides, nitrides, sulfides, and alkali metals. Violent reaction with potassium metal. Contact with acetic anhydride forms a heat-sensitive explosive. On small fires, use water fog. 

ALGOFRENE TYPE 5 (75-43-4) Contact with water causes slow decomposition. Reacts, possibly violently, with barium, sodium, and potassium. Violent reaction with molten aluminum, magnesium. Reacts with acids or acid fumes, producing highly toxic chlorine and fluorine fumes. Attacks chemically active metals alkaline earth, aluminum, copper, magnesium, tin, sodium, potassium, zinc, and their alloys. Undergoes thermal decomposition when... 

Some intramolecular eliminations that occur thermally are known as pyrolytic eliminations, and many of these reactions result in syn elimination. Often these reactions are carried out in the gas phase, where they are not affected by solvent, counterions, or other species that can affect reactions in solution. One of the most-studied pyrolytic eliminations is the Chugaev reaction (equation 10.70). Reaction of an alcohol having a j8-hydrogen atom with sodium or potassium metal or with a strong base... 

Compounds of potassium had been known since ancient times potassium is acaially the seventh most abundant element in the Earth s crust. But this was the first time the metal had been seen and understandably so. Potassium metal reacts with moisture to form hydrogen gas, which catches fire from the heat of the reaction. Davy stored his reactive potassium under naphtha (today used as lighter fluid) and proceeded 2 days later to isolate sodium from caustic soda. But as often happens, Davy s solution of one puzzle provided another. Bases (materials referred to as caustic or alkali) react with acids to form salts and water, which makes them, so to speak, the opposites of acids. When Davy electrolyzed his bases, he found that oxygen was one of the products. Lavoisier had said that oxygen was the acidifying principle, but Davy now showed that it could equally well be considered the principle of bases. Davy dedicated the next 4 years to demonstrating that elements do not behave as principles in the manner Lavoisier had said. 

Detecting peroxides. There may be times when you need to know the peroxide content of a chemical and there are several methods that test for the presence of peroxides, including iodide methods, ferrous thiocyanate methods, titanium sulfate methods, and test strip methods. These methods each have their limitations—some will not detect the presence of all peroxide forms. These methods should not be used to test alkali metals or amides since they react violently with water. Test strips offer some advantages in that they detect a wide group of different peroxides, can be used easily, and are convenient. However, they have limited shelf life and may be beyond the budget of some. For example, potassium iodide-starch test strips are available that can detect peroxides below 100 ppm. The presence of peroxides is detected by deep dark blue (virtually black) color on the test strip from the reaction of iodine (from potassium iodide reaction with peroxide) and starch. We will not discuss these peroxide test methods in detail here, but you should know that they are available. 

Solid potassium metal reacts with water, giving a solution of potassium hydroxide and releasing hydrogen gas. Write a balanced equation for the reaction using complete formulas for the compounds with phase labels. 

The ammonium ions in such salts may be replaced by sodium or potassium upon reaction with the corresponding alkali metal fluorides (Eq. 3.280) ... 

Both reactants m the Williamson ether synthesis usually originate m alcohol pre cursors Sodium and potassium alkoxides are prepared by reaction of an alcohol with the appropriate metal and alkyl halides are most commonly made from alcohols by reaction with a hydrogen halide (Section 4 7) thionyl chloride (Section 4 13) or phosphorus tri bromide (Section 4 13) Alternatively alkyl p toluenesulfonates may be used m place of alkyl halides alkyl p toluenesulfonates are also prepared from alcohols as their imme diate precursors (Section 8 14)... 

Reactions of the Hydroxyl Group. The hydroxyl proton of hydroxybenzaldehydes is acidic and reacts with alkahes to form salts. The lithium, sodium, potassium, and copper salts of sahcylaldehyde exist as chelates. The cobalt salt is the most simple oxygen-carrying synthetic chelate compound (33). The stabiUty constants of numerous sahcylaldehyde—metal ion coordination compounds have been measured (34). Both sahcylaldehyde and 4-hydroxybenzaldehyde are readily converted to the corresponding anisaldehyde by reaction with a methyl hahde, methyl sulfate (35—37), or methyl carbonate (38). The reaction shown produces -anisaldehyde [123-11-5] in 93.3% yield. Other ethers can also be made by the use of the appropriate reagent. 

Potassium superoxide is produced commercially by spraying molten potassium iato an air stream, which may be enriched with oxygen. Excess air is used to dissipate the heat of reaction and to maintain the temperature at ca 300°C. It can also be prepared ia a highly pure state by oxidizing potassium metal that is dissolved ia Hquid ammonia at —50° C. 

The action of redox metal promoters with MEKP appears to be highly specific. Cobalt salts appear to be a unique component of commercial redox systems, although vanadium appears to provide similar activity with MEKP. Cobalt activity can be supplemented by potassium and 2inc naphthenates in systems requiring low cured resin color lithium and lead naphthenates also act in a similar role. Quaternary ammonium salts (14) and tertiary amines accelerate the reaction rate of redox catalyst systems. The tertiary amines form beneficial complexes with the cobalt promoters, faciUtating the transition to the lower oxidation state. Copper naphthenate exerts a unique influence over cure rate in redox systems and is used widely to delay cure and reduce exotherm development during the cross-linking reaction. 

Nucleophilic Substitution Route. Commercial synthesis of poly(arylethersulfone)s is accompHshed almost exclusively via the nucleophilic substitution polycondensation route. This synthesis route, discovered at Union Carbide in the early 1960s (3,4), involves reaction of the bisphenol of choice with 4,4 -dichlorodiphenylsulfone in a dipolar aprotic solvent in the presence of an alkaUbase. Examples of dipolar aprotic solvents include A/-methyl-2-pyrrohdinone (NMP), dimethyl acetamide (DMAc), sulfolane, and dimethyl sulfoxide (DMSO). Examples of suitable bases are sodium hydroxide, potassium hydroxide, and potassium carbonate. In the case of polysulfone (PSE) synthesis, the reaction is a two-step process in which the dialkah metal salt of bisphenol A (1) is first formed in situ from bisphenol A [80-05-7] by reaction with the base (eg, two molar equivalents of NaOH),... 

The superb reduciag power of potassium metal is clearly demoastrated by its facile displacemeat of protoas ia the weakly acidic hydrocarboas (qv), amines, and alcohols (Table 2). Reactions with inorganics and gaseous elements are summarized ia Table 3. 

Potassium Bases. Potassium metal is used to prepare potassium bases from reactions of the metal with alcohols and amines. 

Potassium Hydride. Potassium hydride [7693-26-7] KH, made from reaction of molten potassium metal with hydrogen at ca 200°C, is suppHed in an oil dispersion. Pressure Chemical Company (U.S.) is a principal suppHer. KH is much more effective than NaH or LiH for enolization reactions (63,64). Use of KH as a base and nucleophile has been reviewed (65). 

Potassium Carbonate. Except for small amounts produced by obsolete processes, eg, the leaching of wood ashes and the Engel-Precht process, potassium carbonate is produced by the carbonation, ie, via reaction with carbon dioxide, of potassium hydroxide. Potassium carbonate is available commercially as a concentrated solution containing ca 47 wt % K CO or in granular crystalline form containing 99.5 wt % K CO. Impurities are small amounts of sodium and chloride plus trace amounts (<2 ppm) of heavy metals such as lead. Heavy metals are a concern because potassium carbonate is used in the production of chocolate intended for human consumption. 

Pyrrohdinone forms alkaU metal salts by direct reaction with alkaU metals or their alkoxides or with their hydroxides under conditions in which the water of reaction is removed. The potassium salt prepared in situ serves as the catalyst for the vinylation of 2-pyrrohdinone in the commercial production of A/-vinylpyrrohdinone. The mercury salt has also been described, as have the N-bromo and N-chloro derivatives (61,62). 

Reduction/Reaction with Hydrogen. Tetraduorosilane reacts with hydrogen only above 2000°C. Tetrachlorosilane can be reduced by hydrogen at 1200°C. Tetraio do silane can be reduced to sihcon at 1000°C (165). Reduction of tetraduorosilane with potassium metal to sihcon was the first method used to prepare sihcon (see Silicon and silicon alloys). The reduction of sihcon tetrachloride by ziac metal led to the first semiconductor-grade sihcon (166,167). 

The reaction is displaced to the right by dissociation of sodium hydride and Hberation of hydrogen. This dissociation is favored under vacuum or when the reaction 2one is swept with an inert gas to remove the hydrogen (24,25). In this manner, sodium monoxide substantially free of sodium and sodium hydroxide is produced. In the more compHcated reaction between sodium metal and anhydrous potassium hydroxide, potassium metal and sodium hydroxide are produced in a reversible reaction (42,43) ... 

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