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Aluminium isopropoxide

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Aluminium isopropoxide
One enantiomorph of Al4(OiPr)12
Names
IUPAC name
Aluminium Isopropoxide
Other names
Triisopropoxyaluminium
Aluminium isopropanolate
Aluminium sec-propanolate
Aluminium triisopropoxide
2-Propanol aluminium salt
AIP
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.008.265 Edit this at Wikidata
EC Number
  • 209-090-8
RTECS number
  • BD0975000
UNII
  • InChI=1S/3C3H7O.Al/c3*1-3(2)4;/h3*3H,1-2H3;/q3*-1;+3 checkY
    Key: SMZOGRDCAXLAAR-UHFFFAOYSA-N checkY
  • InChI=1/3C3H7O.Al/c3*1-3(2)4;/h3*3H,1-2H3;/q3*-1;+3
    Key: SMZOGRDCAXLAAR-UHFFFAOYAV
  • CC(C)[O-].CC(C)[O-].CC(C)[O-].[Al+3]
Properties
C9H21AlO3
Molar mass 204.246 g·mol−1
Appearance white solid
Density 1.035 g cm−3, solid
Melting point Sensitive to purity:
138–142 °C (99.99+%)
118 °C (98+%)[1]
Boiling point @10 Torr 135 °C (408 K)
Decomposes
Solubility in isopropanol Poor
Structure
monoclinic
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
 Flammable (F)
GHS labelling:
GHS02: Flammable
Warning
H228
P210, P240, P241, P280
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g. chloroformFlammability 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g. canola oilInstability 2: Undergoes violent chemical change at elevated temperatures and pressures, reacts violently with water, or may form explosive mixtures with water. E.g. white phosphorusSpecial hazards (white): no code
2
1
2
Flash point 16 °C (61 °F; 289 K)
Related compounds
Other cations
 Titanium isopropoxide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
checkY verify (what is checkY☒N ?)

Aluminium isopropoxide is the chemical compound usually described with the formula Al(O-i-Pr)3, where i-Pr is the isopropyl group (–CH(CH3)2). This colourless solid is a useful reagent in organic synthesis.[1]

Structure

[edit]

A tetrameric structure of the crystalline material was verified by NMR spectroscopy and X-ray crystallography. The species is described by the formula Al[(μ-O-i-Pr)2Al(O-i-Pr)2]3.[2][3] The unique central Al is octahedral, and three other Al centers adopt tetrahedral geometry. The idealised point group symmetry is D3.

Preparation

[edit]

This compound is commercially available. Industrially, it is prepared by the reaction between isopropyl alcohol and aluminium, or aluminium trichloride:

2 Al + 6 iPrOH → 2 Al(O-i-Pr)3 +3H2
AlCl3 + 3 iPrOH → Al(O-i-Pr)3 + 3 HCl

The procedure entails heating a mixture of aluminium, isopropyl alcohol, with a small amount of mercuric chloride. The process occurs via the formation of an amalgam of the aluminium. A catalytic amount of iodine is sometimes added to initiate the reaction.[4] The industrial route does not use mercury.[5]

Reactions

[edit]

Aluminium isopropoxide is used in MPV reductions of ketones and aldehydes and the Oppenauer oxidation of secondary alcohols.[6] In these reactions, it is assumed that the tetrameric cluster disaggregates. It is used in the Tishchenko reaction.

Being a basic alkoxide, Al(O-i-Pr)3 has been also investigated as a catalyst for ring opening polymerization of cyclic esters.[7]

History

[edit]

Aluminium isopropoxide was first reported in the master's thesis of the Russian organic chemist Vyacheslav Tishchenko (Вячеслав Евгеньевич Тищенко, 1861–1941), which was reprinted in the Journal of the Russian Physico-Chemical Society (Журнал Русского Физико-Химического Общества) of 1899.[8] This contribution included a detailed description of its synthesis, its peculiar physico-chemical behavior, and its catalytic activity in the Tishchenko reaction (catalytic transformation of aldehydes into esters). It was later found also to display catalytic activity as a reducing agent by Meerwein and Schmidt in the Meerwein–Ponndorf–Verley reduction ("MPV") in 1925.[9][10] 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 isopropoxide.[11]

[edit]
  • Aluminium phenolate
  • Aluminium tert-butoxide, which is a dimer [(t-Bu-O)2Al(μ-O-t-Bu)]2.[12] It is prepared analogously to the isopropoxide.[13]

References

[edit]
  1. ^ a b Ishihara, K.; Yamamoto, H. (2001). "Aluminum Isopropoxide". Encyclopedia of Reagents for Organic Synthesis. John Wiley & Sons. doi:10.1002/047084289X.ra084. ISBN 0471936235.
  2. ^ Folting, K.; Streib, W. E.; Caulton, K. G.; Poncelet, O.; Hubert-Pfalzgraf, L. G. (1991). "Characterization of aluminum isopropoxide and aluminosiloxanes". Polyhedron. 10 (14): 1639–46. doi:10.1016/S0277-5387(00)83775-4.
  3. ^ Turova, N. Y.; Kozunov, V. A.; Yanovskii, A. I.; Bokii, N. G.; Struchkov, Yu T.; Tarnopolskii, B. L. (1979). "Physico-chemical and structural investigation of aluminium isopropoxide." J. Inorg. Nucl. Chem. 41(1): 5-11, doi:10.1016/0022-1902(79)80384-X.
  4. ^ Young, W.; Hartung, W.; Crossley, F. (1936). "Reduction of Aldehydes with Aluminum Isopropoxide". J. Am. Chem. Soc. 58: 100–102. doi:10.1021/ja01292a033.
  5. ^ Otto Helmboldt; L. Keith Hudson; Chanakya Misra; Karl Wefers; Wolfgang Heck; Hans Stark; Max Danner; Norbert Rösch. "Aluminum Compounds, Inorganic". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a01_527.pub2. ISBN 978-3527306732.
  6. ^ Eastham, Jerome F.; Teranishi, Roy (1955). "Δ4-Cholesten-3-one". Organic Syntheses. 35: 39. doi:10.15227/orgsyn.035.0039.
  7. ^ Tian, D.; Dubois, Ph.; Jérôme, R. (1997). "Macromolecular Engineering of Polylactones and Polylactides. 22. Copolymerization of ε-Caprolactone and 1,4,8-Trioxaspiro[4.6]-9-undecanone Initiated by Aluminum Isopropoxide". Macromolecules. 30 (9): 2575–2581. doi:10.1021/ma961567w.
  8. ^ Тищенко, B. E. (Tishchenko, V. E.) (1899). "Действие амальгамированного алюминия на алкоголь. Алкоголятов алюминия, их свойства и реакции" [Effect of amalgamated aluminium on alcohol. Aluminium alkoxides, their properties and reactions.]. Журнал Русского Физико-Химического Общества (Journal of the Russian Physico-Chemical Society) (in Russian). 31: 694–770.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  9. ^ Meerwein, H.; Schmidt, R. (1925). "Ein neues Verfahren zur Reduktion von Aldehyden und Ketonen" [A new procedure for the reduction of aldehydes and ketones]. Justus Liebigs Ann. Chem. (in German). 444: 221–238. doi:10.1002/jlac.19254440112.
  10. ^ Wilds, A. L. (1944). "Reduction with Aluminum Alkoxides (The Meerwein-Ponndorf-Verley Reduction)". Org. React. 2 (5): 178–223. doi:10.1002/0471264180.or002.05.
  11. ^ Oppenauer, R. V. (1937). "Eine Methode der Dehydrierung von Sekundären Alkoholen zu Ketonen. I. Zur Herstellung von Sterinketonen und Sexualhormonen" [Dehydration of secondary alcohols to ketones. I. Preparation of sterol ketones and sex hormones]. Recl. Trav. Chim. Pays-Bas (in German). 56 (2): 137–144. doi:10.1002/recl.19370560206.
  12. ^ Holleman, A. F.; Wiberg, E. (2001). Inorganic Chemistry. San Diego: Academic Press. ISBN 0-12-352651-5.
  13. ^ Wayne, Winston; Adkins, Homer (1941). "Aluminum tert-Butoxide". Organic Syntheses. 21: 8. doi:10.15227/orgsyn.021.0008.
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