Hypophosphites

Triethylammonium formate is another reducing agent for q, /3-unsaturated carbonyl compounds. Pd on carbon is better catalyst than Pd-phosphine complex, and citral (49) is reduced to citronellal (50) smoothly[55]. However, the trisubstituted butenolide 60 is reduced to the saturated lactone with potassium formate using Pd(OAc)2. Triethylammonium formate is not effective. Enones are also reduced with potassium formate[56]. Sodium hypophosphite (61) is used for the reduction of double bonds catalyzed by Pd on charcoal[57]. 

Hypophosphite, see under Phosphinate Ice, see Hydrogen oxide (solid)... 

Perchloric acid Acetic acid, acetic anhydride, alcohols, antimony compounds, azo pigments, bismuth and its alloys, methanol, carbonaceous materials, carbon tetrachloride, cellulose, dehydrating agents, diethyl ether, glycols and glycolethers, HCl, HI, hypophosphites, ketones, nitric acid, pyridine, steel, sulfoxides, sulfuric acid... 

Cm ORINE OXYGEN ACIDS AND SALTS - DICm ORINE MONOXIDE, HYPOCm OROUS ACID, AND HYPOCm ORITES] (Vol 5) Barium hypophosphite [14871-79-5]... 

Reductions. Hydrazine is a very strong reducing agent. In the presence of oxygen and peroxides, it yields primarily nitrogen and water with more or less ammonia and hydrazoic acid [7782-79-8]. Based on standard electrode potentials, hydrazine in alkaline solution is a stronger reductant than sulfite but weaker than hypophosphite in acid solution, it falls between and Ti ( 7). 

In electroless deposition, the substrate, prepared in the same manner as in electroplating (qv), is immersed in a solution containing the desired film components (see Electroless plating). The solutions generally used contain soluble nickel salts, hypophosphite, and organic compounds, and plating occurs by a spontaneous reduction of the metal ions by the hypophosphite at the substrate surface, which is presumed to catalyze the oxidation—reduction reaction. 

However, hydrogen is formed in two side reactions, ie, by the decomposition of some sodium hypophosphite (eq. 2) and by the direct reaction of phosphoms with sodium hydroxide (eq. 3). 

The remaining 15% of the elemental P is used in P -dependent apphcations which require the element as a direct reactant. The principal products include P2S5, PCl and POCl, 2 5 hypophosphite, with much smaller amounts leading to PH, red P, phosphonates, and various other phosphoms derivatives. Pinal apphcations include flame retardants (qv), lubricant additives, insecticides, herbicides, water treatment, cleaning compounds, plastici2ers, and semiconductors (14). 

The reaction proceeds quantitatively and the hydroiodic acid can be removed by repeated distillation at 5.3 kPa (40 mm Hg), leaving pure H2PO2 as the product. Phosphinic acid may also be prepared by the treatment of barium hypophosphite [14871-79-5] with a stoichiometric quantity of sulfuric acid to precipitate barium sulfate. 

Commercially, phosphinic acid and its salts are manufactured by treatment of white phosphoms with a boiling slurry of lime. The desired product, calcium phosphinite [7789-79-9], remains ia solution andiasoluble calcium phosphite [21056-98-4] is precipitated. Hydrogen and phosphine are also formed, the latter containing sufficient diphosphine to make it spontaneously flammable. The details of this compHcated reaction, however, are imperfectly understood. Under some conditions, equal amounts of phosphoms appear as phosphine and phosphite, and the volume of the hydrogen Hberated is nearly proportional to the hypophosphite that forms. 

In addition, a small amount of decomposition of hypophosphite by alkaU occurs. 

Excess calcium hydroxide is precipitated by usiag carbon dioxide and the calcium carbonate, calcium hydroxide, and calcium phosphite are removed by filtration. The filtered solution is treated with an equivalent amount of sodium sulfate or sodium carbonate to precipitate calcium sulfate or carbonate. Sodium hypophosphite monohydrate [10039-56-2] is recovered upon concentration of the solution. Phosphinic acid is produced from the sodium salt by ion exchange (qv). The acid is sold as a 50 wt %, 30—32 wt %, or 10 wt % solution. The 30—32 wt % solution is sold as USP grade (Table 12) (63). Phosphinic acid and its salts are strong reduciag agents, especially ia alkaline solution (65). 

A principal commercial appHcation of the hypophosphites is ia the electroless plating (qv) process. Nickel salts are chemically reduced by hypophosphites to form a smooth adherent nickel plating to protect the iateriors of large vessels and tank cars. The coating, which can be hardened by heat treatment, usually contains 8—10 wt % phosphoms and is highly impervious. 

Phosphine is also made as a by-product of the commercial calcium hypophosphite [7789-79-9]. Calcium phosphite [21056-98-4] is also produced. 

Approximately 4500 tons of sodium hypophosphite [7681-53-0] NaH2P02, was produced in 1990. This material is used principally in electroless nickel plating of plastic objects. Of the secondary products made from primary phosphoms compounds, phosphoms oxychloride is manufactured in the largest volume. Phosphoms pentachloride and phosphoms sulfochloride are made from phosphoms trichloride. 

Hand in hand with this research on finding a suitable carboxyUc acid chemical for cross-linker has been the search for an economical catalyst system. The catalyst found to be most effective for the esterification reaction was sodium hypophosphite (NaH2P02). This material was also costiy and out of range for the textile industry. Because weak bases function as catalyst, a range of bases has been explored, including the sodium salts of acids such as malic acid. 

Distibines and Distibenes. A considerable number of tetraalkyl- and tetraaryldistibines have been investigated. These are usually obtained by the reduction of a dialkyl- or diaryUialostibine with sodium hypophosphite (111,112) or magnesium (108,116). Distibines can also be prepared by the treatment of a metal dialkyl- or diarylstibide with a 1,2-dihaloethane (70,71,77,85,91,128)... 

Modem electroless plating began in 1944 with the rediscovery that hypophosphite could bring about nickel deposition (7,8). Subsequent work led to the first patents on commercially usable electroless nickel solutions. Although these solutions were very useful for coating metals, they could not be used on most plastics because the operating temperature was 90—100°C. The first electroless nickel solution capable of wide use on plastics was introduced in 1966 (9). This solution was usable at room temperature and was extremely stable (see Nickel and nickel alloys). 

Deposition reactions for some reducing agents are given in Table 1 hydrogen is a principal by-product of each reduction. Elemental phosphoms or boron is codeposited with the reduced metal from hypophosphite, borohydride, or organoborane baths (15). Other minor reactions can also occur (18). All of these reductions can be viewed as dehydrogenation reactions (16,19). 

Electroless nickel—boron baths use sodium borohydride or dimethylamine borane [74-94-2] in place of sodium hypophosphite (see Boron compounds). The nickel—boron aHoy is brittle, highly stressed, and much more expensive than nickel—phosphoms aHoys. Nickel—boron is mainly used to replace gold in printed circuit board plating. 

Sodium borohydride or dimethylarnine borane have found limited use as reduciag agents because of expense. In addition, bath stabiHty, plating rate, and deposit properties are inferior to those of formaldehyde-reduced baths. The deposit is a copper—boron alloy. Copper—hypophosphite baths have been iavestigated, but these are poorly autocatalytic, and deposit only very thin coatings. 

Pd-C, R0H,.HC02NH4J hydrazine or sodium hypophosphite, 42-91% yield. 2-Benzylaminopyridine and benzyladenine were stable to these reaction conditions. Lower yields occurred because of the water solubility of the product, thus hampering isolation. 

Barium hypophosphite (H2O) [14871-79-5] M 285.4. Ppted from aq soln (3mL/g) by adding EtOH. 

Hydrazoic acid Hydrides, volatile Hydrogen cyanide (unstabilized) Hydrogen (low pressure) Hydrogen peroxide (> 35% water) Magnesium peroxide Mercurous azide Methyl acetylene Methyl lactate Nickel hypophosphite Nitriles > ethyl Nitrogen bromide... 

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