Sodium aluminium hydride: Difference between revisions

| Verifiedfields = changed

| Watchedfields = changed

| verifiedrevid = 443346228

| ImageFile1 = CaWO4.tif

| ImageSize1 =

| ImageFile2 = File:NaAlH4.png

| ImageSize2 =

|SystematicName=Sodium alumanuide

|Section1={{Chembox Identifiers

| CASNo_Ref = {{cascite|correct|??}}

| CASNo = 13770-96-2

| EINECS = 237-400-1

| PubChem = 26266

| InChI = 1S/Al.Na.4H/q-1;+1;;;;

| SMILES = [Na+].[AlH4-]

| UNNumber = 2835

|Section2={{Chembox Properties

| Na=1 | Al=1 | H=4

| Appearance = White or gray crystalline solid

| Density = 1.24 g/cm³

| MeltingPtC = 178

| BoilingPt =

| Solubility =

| SolubleOther = soluble in [[tetrahydrofuran|THF]] (16 g/100 mL at room temperature)

|Section3={{Chembox Hazards

| ExternalSDS = [https://www.fishersci.com/store/msds?partNumber=AC380110250&productDescription=SODIUM+ALUMINIUM+HYDRIDE+25GR&vendorId=VN00032119&countryCode=US&language=en Fisher Scientific]

| FlashPtF = -7

| AutoignitionPtC = 185

| GHSPictograms = {{GHS02}}{{GHS05}}{{GHS07}}

| NFPA-H = 3

| NFPA-F = 2

| NFPA-I = 0

| NFPA-S = W

| LD50 = 740 mg/kg (oral, mouse)

'''Sodium aluminium hydride''' or '''sodium alumanuide''' is an [[inorganic compound]] with the [[chemical formula]] NaAlH₄. It is a white [[pyrophoricity|pyrophoric]] solid that dissolves in [[tetrahydrofuran|tetrahydrofuran (THF)]], but not in [[diethyl ether]] or hydrocarbons. It has been evaluated as an agent for the reversible storage of hydrogen and it is used as a [[reagent]] for the [[chemical synthesis]] of [[organic compound]]s. Similar to [[lithium aluminium hydride]], it is a [[salt (chemistry)|salt]] consisting of separated [[sodium]] [[cations]] and tetrahedral AlH{{su|b=4|p=−}} [[anion]]s.<ref name="ACB">J. W. Lauher, D. Dougherty P. J. Herley "Sodium tetrahydroaluminate" Acta Crystallogr. 1979, volume B35, pp.1454-1456. {{doi|10.1107/S0567740879006701}}</ref>

==Structure, preparation, and reactions==

Sodium tetrahydroaluminate adopts the structure of (is isostructural with) [[calcium tungstate]]. As such, the tetrahedral AlH{{su|b=4|p=−}} centers are linked with eight-coordinate Na+ cations.<ref name="ACB" />

The compound is prepared from the elements under high pressures of H₂ at 200&nbsp;°C using [[triethylaluminium]] catalyst:<ref>Peter Rittmeyer, Ulrich Wietelmann "Hydrides" in Ullmann's Encyclopedia of Industrial Chemistry, 2002, Wiley-VCH, Weinheim. {{doi|10.1002/14356007.a13_199}}</ref>

:Na + Al + 2 H₂ → NaAlH₄

As a suspension in diethyl ether, it reacts with [[lithium chloride]] to give the popular reagent [[lithium aluminium hydride]]:

:LiCl + NaAlH₄ → LiAlH₄ + NaCl

The compound reacts rapidly, even violently, with [[protic solvent|protic]] reagents, such as water, as described in this idealized equation:

:4 H₂O + NaAlH₄ → "NaAl(OH)₄" + 4 H₂

==Applications==

===Hydrogen storage===

Sodium alanate<ref>[https://books.google.com/books?id=LgEXet3y4PQC&dq=sodium+alanate&pg=PA45 Computational Study of Pristine and Titanium-doped Sodium Alanates for ...]</ref> has been explored for [[hydrogen storage]] in [[hydrogen tank]]s.<ref>{{ cite journal |author1=Zaluska, A. |author2=Zaluski, L. |author3=Ström-Olsen, J. O. | title = Sodium Alanates for Reversible Hydrogen Storage | journal = Journal of Alloys and Compounds | year = 2000 | volume = 298 | issue = 1–2 | pages = 125–134 | doi = 10.1016/S0925-8388(99)00666-0 }}</ref> The relevant reactions are:

: 3 NaAlH₄ → Na₃AlH₆+ 2 Al + 3 H₂

: Na₃AlH₆ → 3 NaH + Al + 3/2 H₂

Sodium tetrahydroaluminate can release up to 7.4 wt % of hydrogen when heated at {{convert|200|°C|°F}}. [[Absorption (chemistry)|Absorption]] can be slow, with several minutes being required to fill a tank. Both release and uptake are catalysed by [[titanium]].<ref>{{ cite web | url = http://phys.org/news123307288.html | title = Researchers Solve Decade-Old Mystery of Hydrogen Storage Material | publisher = Phys.Org | date = 2008-02-27 }}</ref>

===Reagent in organic chemistry===

Sodium aluminium hydride is a strong [[reducing agent]], very similar in reactivity to [[lithium aluminium hydride]] (LAH) and, to some extent, [[Diisobutylaluminium hydride]] (DIBAL) in organic reactions.<ref>Melinda Gugelchuk "Sodium Aluminum Hydride" Encyclopedia of Reagents for Organic Synthesis, 2001, John Wiley. {{doi|10.1002/047084289X.rs039}}</ref> It is much more powerful reducing agent than [[sodium borohydride]] due to the weaker and more [[polar bond|polar]] Al-H bond compared to the B-H bond. Like LAH, it reduces [[ester]]s to [[Alcohol (chemistry)|alcohol]]s.

==Safety==

Sodium aluminium hydride is highly flammable. It does not react in dry air at room temperature but is very sensitive to moisture. It ignites or explodes on contact with water.

{{sodium compounds}}

{{aluminium compounds}}

[[Category:Aluminium complexes]]

[[Category:Reducing agents]]