Lithium aluminum hydride, hazards

Tetrahydrofuran was dried and distilled from lithium aluminum hydride prior to use. For a warning concerning potential hazards of this procedure, see Org. Syn., Coll. Vol. 5, 970 (1973). 

The tetrahydrofuran was freshly distilled from lithium aluminum hydride. See Org. Syn., 46, 105 (1966) for a note concerning the hazards involved in purifying tetrahydrofuran. 

Lithium aluminum hydride in tetrahydrofuran was purchased from Aldrich Chemical Company, Inc., and was handled in the fashion described above for the Grignard solution (see Note 3). While solid lithium aluminum hydride can be used (with appropriate changes 1n the amount of solvent initially used), the hazards of handling this flammable and even explosive reagent (see references 4 and 5) can be reduced by using the pre-prepared solution. 

Reduction of amides. Sodium borohydride combined with methanesulfonic acid in DMSO reduces amides to the corresponding amines in 60-90% isolated yield. I he system also reduces acids and esters to primary alcohols. These reductions have been conducted with lithium aluminum hydride and with borane-tetrahydrofurane (5,48),2 hut with somewhat different selectivities. This new reagent, however, appears to be less hazardous than the latter reagent. 

Bro Yes. The same is true with the Lithium aluminum Hydride. Except that a duty tax of 4% of the total cost of the item is required before it is released. This is most likely due to the fact that it is listed as hazardous material and they J ust want to milk you for some money because the stuff requires them to tiptoe when carrying it. ... 

Reduction of ketones. Bernstein and co-workers " found the reduction of the 11-ketosteroid (1) to cortisol 3,20-bisethyleneketal (2) with lithium aluminum hydride unsatisfactory with respect to yield, safety hazard, etc., but found that the reduction can be accomplished in high yield with an exceedingly large excess of sodium... 

A Ventron bulletin recommends addition of the metal hydride from an Erlen-meyer attached to the flask by Gooch tubing (Fig. A-1). Diethyl ether and dioxane may be dried effectively with lithium aluminum hydride without hazard provided that the solvent is not distilled to dryness. 

This method avoids the hazards involved with the use of lithium aluminum hydride and is considerably less complicated. 

The previously published method for the liberation of the diol from the resolved 1,1 -b1naphthyl-2,2 -diyi hydrogen phosphate entailed esterification with diazomethane and reductive cleavage with lithium aluminum hydride. The procedure presented here is felt to be safer in that it circumvents hazards associated with using diazomethane and lithium aluminum hydride on a large scale. 

Ethyl ether presents a fire and/or explosion hazard when it comes in contact with strong oxidizers such as ozone (due to ethyl peroxide), permanganate-concentrated H2SO4, perchloric acid and perchlorates, many organic peroxides, sodium and potassium peroxides (catches fire), chromic acid, liquid air, and chlorine (NFPA 1986). Explosions have occurred when ethyl ether is distilled with lithium aluminum hydride or aluminum chloride. The presence of carbon dioxide in ether has been attributed to such explosions. 

Handling, Storage, and Precautions neat liquid is pyrophoric solutions react very vigorously with air and with H2O, and related compounds, giving rise to fire hazards use in a fume hood, in the absence of oxygen and moisture (see Lithium Aluminum Hydride for additional precautions) THE solutions should only be used below 70 °C, as above that temperature ether cleavage is problematic. 

Most metal hydrides react violently with water with the evolution of hydrogen, which can form an explosive mixture with air. Some, such as lithium aluminum hydride, potassium hydride, and sodium hydride, are pyrophoric. Most can be decomposed by gradual addition of (in order of decreasing reactivity) methyl alcohol, ethyl alcohol, n-butyl alcohol, or t-butyl alcohol to a stirred, ice-cooled solution or suspension of the hydride in an inert liquid, such as diethyl ether, tetrahydrofuran, or toluene, under nitrogen in a three-necked flask. Although these procedures reduce the hazard and should be a part of any experimental procedure that uses reactive metal hydrides, the products from such deactivation may be hazardous waste that must be treated as such on disposal. 

Hydrides commonly used in laboratories are lithium aluminum hydride, potassium hydride, sodium hydride, sodium borohydride, and calcium hydride. The following methods for their disposal demonstrate that the reactivity of metal hydrides varies considerably. Most hydrides can be decomposed safely by one of the four methods, but the properties of a given hydride must be well understood in order to select the most appropriate method. (CAUTION Most of the methods described below produce hydrogen gas, which can present an explosion hazard. The reaction shouid be carried out in a hood, behind a shield, and with proper safeguards to avoid exposure of the effluent gas to spark or flame. Any stirring device must be spark-proof.)... 

Lithium aluminum hydride is highly corrosive to the skin, eyes, and mucous membranes. Contact with moisture forms lithium hydroxide, which can cause severe bums. Powdered LAH forms dusts that can pose an inhalation hazard. Ingestion of this substance may cause aching muscles, nausea, vomiting, dizziness, and unconsciousness and may be fatal. Ingestion can result in gas embohsm due to the formation of hydrogen. 

Reduction, which consists of loss of O, gain of H, or gain of electrons by a chemical species, is also a common operation in chemical synthesis. As is the case with oxidants, the reagents used to accomplish reduction can pose hazards and produce undesirable by-products. Such reductants include lithium aluminum hydride, LiAlH4, and tributyl tin hydride. 

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