Aluminium isopropoxide
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{{Chembox new
| Name = Aluminium isopropoxide
| ImageFile = Al4(OiPr)12.png
<!-- | ImageSize = 350px -->
| ImageName = One enantiomorph of Al<sub>4</sub>(OiPr)<sub>12</sub>
| IUPACName = Aluminium Isopropoxide
| OtherNames = Triisopropoxyaluminium<br /> Aluminium isopropanolate<br /> Aluminium sec-propanolate<br /> Aluminium triisopropoxide<br /> 2-Propanol aluminium salt<br /> AIP
| Section1 = {{Chembox Identifiers
| SMILES = CC(C)O[[Al]](OC(C)C)OC(C)C
| CASNo = 555-31-7
| RTECS = BD0975000
}}
| Section2 = {{Chembox Properties
| Formula = C<sub>9</sub>H<sub>21</sub>O<sub>3</sub>Al
| MolarMass = 204.25 g/mol
| Appearance = white solid
| Density = 1.035 g/cm³, solid
| Solubility = Decomposes
| Solvent = [[isopropanol]]
| SolubleOther = Soluble
| MeltingPt = Sensitive to purity:<br /> 138–142 °C (99.99+%)<br /> 118 °C (98+%)<ref>Ishihara, K.; Yamamoto, H. "Aluminum Isopropoxide" in Encyclopedia of Reagents for Organic Synthesis, 2001 John Wiley. DOI: 10.1002/047084289X.ra084</ref>
| BoilingPt = @10 [[torr]] 135 °C (408 K)
}}
| Section3 = {{Chembox Structure
| CrystalStruct = [[monoclinic]]
}}
| Section7 = {{Chembox Hazards
| MainHazards = Flammable ('''F''')
| NFPA-H = 2
| NFPA-R = 2
| NFPA-F = 1
| FlashPt = 16 °C
| RPhrases = {{R11}}
| SPhrases = {{S8}}, {{S16}}
}}
}}
'''Aluminium isopropoxide''' is the [[chemical compound]] usually described with the formula Al(O-i-Pr)<sub>3</sub>, where i-Pr is the [[isopropyl]] group (CH(CH<sub>3</sub>)<sub>2</sub>). This colourless solid is a useful [[reagent]] in [[organic synthesis]]. The structure of this compound is complex, possibly time-dependent, and may depend on solvent.
==Structure==
The structure of the metal alkoxides are often complex and aluminium isopropoxide is no exception. The complexity is also reflected in the disputed melting point for the material which could reflect the presence of trace impurities, such as water, slow oligomerisation ("aging") or both. The tetrameric structure was verified by [[NMR spectroscopy]] and [[X-ray crystallography]]. The species is described by the formula Al[[(μ-O-i-Pr)<sub>2</sub>Al(O-i-Pr)<sub>2</sub>]]<sub>3</sub>.<ref>{{cite journal | author = Folting, K.; Streib, W. E.; Caulton, K. G.; Poncelet, O.; Hubert-Pfalzgraf, L. G. | title = Characterization of aluminum isopropoxide and aluminosiloxanes | journal = [[Polyhedron (journal)|Polyhedron]] | year = 1991 | volume = 10 | pages = 1639–46 | doi = 10.1016/S0277-5387(00)83775-4}}</ref><ref>Turova, N. Y.; Fozunov, V. A.; Yanovskii, A. I.; Bokii, N. G.; Struchkov, Yu T.; Tarnopolskii, B. L. Journal of Inorganic and Nuclear Chemistry 1979, volume 41, p. 5.</ref> The unique central Al is octahedral surrounded by three bidentate "[[Al(O-i-Pr)<sub>4</sub>]]<sup>-</sup>" [[ligand]]s, each featuring tetrahedral Al. The idealised [[symmetry group|point group symmetry]] is ''D<sub>3</sub>''. The tert-butoxide is a dimeric with the formula Al<sub>2</sub>(μ-O-t-Bu)<sub>2</sub>(O-t-Bu)<sub>4</sub><ref>{{cite book | author = Holleman, A. F.; Wiberg, E. | title = Inorganic Chemistry | publisher = [[Academic Press]] | location = San Diego | year = 2001 | isbn = 0-12-352651-5}}</ref> It is prepared analogously to the isopropoxide.<ref>{{OrgSynth | author = Wayne, W.; Adkins. H. | title = Aluminum tert-Butoxide | collvol = 3 | collvolpages = 48 | year = 1955 | prep = cv3p0048}}</ref>
==Preparation==
A widely accepted method for preparing aluminium isopropoxide was published in 1936 by Young, Hartung, and Crossley.<ref>{{cite journal | author = Young, W.; Hartung, W.; Crossley, F. | title = Reduction of Aldehydes with Aluminum Isopropoxide | journal = [[J. Am. Chem. Soc.]] | volume = 58 | pages = 100–2 | year = 1936 | doi = 10.1021/ja01292a033}}</ref> Their procedure entails heating a mixture of 100 g of aluminium, 1200 mL of [[isopropyl alcohol]], and 5 g of [[mercuric chloride]] at reflux. The process occurs via the formation of an [[amalgam]] of the aluminium. A catalytic amount of iodine is sometimes added to initiate the reaction, which can be quite vigorous. Young et al. achieved an 85-90% yield, after purification by distillation at 140-150 °C (5 mm Hg).
==Reactions==
In a MPV reduction, [[ketones]] and [[aldehydes]] are reduced to alcohols concomitant with the formation of acetone. This reduction relies on an equilibrium process, hence it produces the thermodynamic product. Conversely, in the Oppenauer Oxidation, secondary alcohols are converted to ketones,<ref name = eastham/> and homoallylic alcohols are converted to α,β-unsaturated [[carbonyl]]s.<ref name = eastham>{{OrgSynth | author = Eastham, J. F.; Teranishi, R. | title = Δ4-Cholesten-3-one | collvol = 4 | pages = 192 | year = 1963 | prep = cv4p0192}}</ref> In these reactions, it is assumed that the tetrameric cluster disagregates.
[[Image:MPV-reduction.png|400px]]
Being a basic [[alkoxide]], Al(O-i-Pr)<sub>3</sub> has been also investigated as a [[catalyst]] for [[ring opening polymerization]] of [[cyclic ester]]s.<ref>{{cite journal | author = Tian, D.; Dubois, Ph.; Jérôme, R. | title = <nowiki>Macromolecular Engineering of Polylactones and Polylactides. 22. Copolymerization of ε-Caprolactone and 1,4,8-Trioxaspiro[4.6]-9-undecanone Initiated by Aluminum Isopropoxide</nowiki> | journal = [[Macromolecules (journal)|Macromolecules]] | year = 1997 | volume = 30 | pages = 2575–2581 | doi = 10.1021/ma961567w}}</ref>
==History==
Aluminium isopropoxide was first reported as a reducing agent by [[Hans Meerwein|Meerwein]] and Schmidt in the [[Meerwein-Ponndorf-Verley reduction]] ("MPV") in 1925.<ref>{{cite journal | author = Meerwein, H.; Schmidt, R. | title = Ein neues Verfahren zur Reduktion von Aldehyden und Ketonen | journal = [[Justus Liebig's Annalen der Chemie]] | year = 1925 | volume = 444 | pages = 221–238 | doi = 10.1002/jlac.19254440112}}</ref> The reverse of the MPV reaction, oxidation of an alcohol to a ketone, is termed the [[Oppenauer oxidation]]. The original Oppenauer oxidation employed aluminium butoxide in place of the isoproxide.<ref>{{cite journal | author = Oppenauer, R. V. | title = Dehydration of secondary alcohols to ketones. I. Preparation of sterol ketones and sex hormones | journal = [[Recueil des Travaux Chimiques des Pays-Bas et de la Belgique]] | year = 1937 | volume = 56 | pages = 137–44}}</ref>
==References==
<references/>
[[Category:Alkoxides]]
[[Category:Aluminium compounds]]
[[ar:إيزوبروبوكسيد ألومنيوم]]
[[ja:アルミニウムイソプロポキシド]]
[[lv:Alumīnija izopropoksīds]]
[[zh:异丙醇铝]]