7784-21-6 Usage
Description
Aluminium hydride, also known as aluminum hydride, is a colorless to white solid with chemical properties of a nonvolatile compound. It is a relatively unstable polymeric covalent hydride that has been known for its potential applications in various industries. Aluminium hydride can be obtained by reacting an ether solution of AlCl3 with LiH.
Uses
1. Used in Chemical Synthesis:
Aluminium hydride is used as a catalyst for organic polymerization processes, facilitating the formation of polymers from monomers. This application is crucial in the production of various plastics, resins, and other materials.
2. Used as a Reducing Agent:
Aluminium hydride serves as a reducing agent in chemical reactions, helping to convert other compounds into simpler forms. This property makes it valuable in the synthesis of various chemicals and pharmaceuticals.
3. Used in Energy Production (Historic):
In the mid-1960s, Aluminium hydride received significant attention for its potential as a high-energy additive to solid rocket propellants. However, despite intense research and development, commercial manufacture has not been undertaken due to the high cost of synthetic methods and the compound's instability.
4. Used in Aluminum Plating (Theoretical):
Aluminium hydride was once considered for use in aluminum plating, a process that involves coating a surface with a thin layer of aluminum to improve its appearance, corrosion resistance, or electrical conductivity. However, this application never materialized due to the challenges associated with the compound's instability and the development of more efficient methods.
Physical Properties:
Aluminium hydride is a colorless cubic crystal that is very unstable and decomposes in water. Its decomposition enthalpy (ΔΗ°) is approximately 11.0 kcal/mol (-46.0 kJ/mol).
Preparation
Aluminum hydride is prepared by the reaction of lithium hydride with aluminum chloride in diethyl ether.
3LiH + AlCl3 → AlH3 + 3LiCl
Air & Water Reactions
Ignites in moist air. Ignites in air with or without oxygen enrichment [Bretherick 1979 p. 221]. Explosively hydrolyzed by water (forms hydrogen gas) [Ruff J.K. Inorg. Synth 1967, 9, 34].
Reactivity Profile
Aluminium hydride is a powerful reducing agent. May react violently with oxidizers. Prolonged exposure to heat may cause spontaneous decomposition. Can also decompose spontaneously at ambient temperature with explosive violence. Occasionally, explosions have occurred when Aluminium hydride was stored in ether. The explosions have been blamed on the presence of carbon dioxide impurity in the ether [J. Amer. Chem. Soc. 70:877 1948]. Can emit toxic fumes on contact with acid or fumes from an acid. [Lewis]. At elevated temperatures, the hydride reduces carbon dioxide or sodium hydrogen carbonate to methane and ethane. These gases are the explosive products formed when CO2 extinguishers have been used during hydride fires. The 1:1 complexes of the hydride (as a complex with ether or dimethylamine) and various tetrazole derivatives are explosive. Tetrazoles include, 2-methyl, 2-ethyl, 5-ethyl, 2-methyl-5-vinyl, 5-amino-2-ethyl, etc., [US Pat. 3 396 170, 1968].
Safety Profile
Hydrides of some metals (such as ASH3 are extremely toxic. Dangerous fire hazard. An unstable material which is spontaneously flammable in air or O2. Evolves explosive H2 upon contact with moisture. Severe explosion hazard by chemical reaction wherein H2 gas is produced, also in contact with methyl ethers contaminated by Con. Mixtures with tetrazole derivatives are explosive. Reacts with oxidzing materials. On contact with acid or acid fumes, it can emit toxic fumes. See also HYDRIDES and ALUMINUM COMPOUNDS.
Check Digit Verification of cas no
The CAS Registry Mumber 7784-21-6 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 7,7,8 and 4 respectively; the second part has 2 digits, 2 and 1 respectively.
Calculate Digit Verification of CAS Registry Number 7784-21:
(6*7)+(5*7)+(4*8)+(3*4)+(2*2)+(1*1)=126
126 % 10 = 6
So 7784-21-6 is a valid CAS Registry Number.
InChI:InChI=1S/Al.3H
7784-21-6Relevant articles and documents
Catalytic synthesis of aluminum hydride in the presence of palladium black
Normatov
, p. 558 - 560 (2004)
The catalytic properties of a palladium catalyst in the formation of aluminum hydride are studied. The formation of stoichiometric aluminum hydride is determined by XRD, DTA, and spectrophotometry. Findings are rationalized in terms of the electron-chemical catalytic scheme.
Surface changes on AlH3 during the hydrogen desorption
Kato, Shunsuke,Bielmann, Michael,Ikeda, Kazutaka,Orimo, Shin-Ichi,Borgschulte, Andreas,Zuettel, Andreas
, (2010)
Surface change of α -AlH3 during the hydrogen desorption was investigated by means of in situ x-ray photoelectron spectroscopy combined with thermal desorption spectroscopy. The surface of AlH3 covered by an oxide layer significantly changes upon hydrogen desorption and the hydrogen desorption rate increases remarkably. In this study, the role of the surface oxide layer on AlH3 in view of the hydrogen desorption kinetics was investigated. AlH3 only decomposes into Al and H2 at the free surface and not in the bulk. Therefore, a closed surface oxide layer prevents the thermodynamically unstable AlH3 from decomposition.
Aluminium hydride: A reversible material for hydrogen storage
Zidan, Ragaiy,Garcia-Diaz, Brenda L.,Fewox, Christopher S.,Stowe, Ashley C.,Gray, Joshua R.,Harter, Andrew G.
, p. 3717 - 3719 (2009)
Aluminium hydride has been synthesized electrochemically, providing a synthetic route which closes a reversible cycle for regeneration of the material and bypasses expensive thermodynamic costs which have precluded AlH3 from being considered as
Oxazolidines as Intermediates in the Asymmetric Synthesis of 3-Substituted and 1,3-Disubstituted Tetrahydroisoquinolines
Raghavan, Sadagopan,Senapati, Puspamitra
, p. 6201 - 6210 (2016/08/16)
A diastereoselective mercury(II)-promoted intramolecular cyclization of unsaturated aldehyde via an oxazolidine to prepare C-3-substituted tetrahydroisoquinoline is disclosed. The C-3 stereogenic center is subsequently exploited to create the C-1 stereocenter by coordination of the nucleophilic reagent to the oxygen atom of oxazolidine. Both cis- and trans-1,3-disubstituted tetrahydroisoquinolines can be readily prepared. In addition, when a cationic rhodium complex was used, intramolecular hydroamination was effected, thus avoiding mercury(II) salts and demercuration. The reaction is general and works well using aliphatic and aromatic aldehydes.
Hydrogen release reactions of Al-based complex hydrides enhanced by vibrational dynamics and valences of metal cations
Sato,Ramirez-Cuesta,Daemen,Cheng,Tomiyasu,Takagi,Orimo
supporting information, p. 11807 - 11810 (2016/10/09)
Hydrogen release from Al-based complex hydrides composed of metal cation(s) and [AlH4]- was investigated using inelastic neutron scattering viewed from vibrational dynamics. The hydrogen release followed the softening of translational and [AlH4]- librational modes, which was enhanced by vibrational dynamics and the valence(s) of the metal cation(s).
