Di-tert-butyl chromate

Chemical compound From Wikipedia, the free encyclopedia

Di-tert-butyl chromate is an alkoxide with the formula CrO2(OC(CH3)3)2. It forms red crystals at temperatures below −5 °C, above which it melts to give a red oil.[3][4] The complex, which is diamagnetic, is of fundamental interest as a model for the intermediates in oxidations of alcohols by chromium(VI). This ester is stable because tertiary alcohols such as tert-butyl alcohol lack alpha hydrogens, stopping the E2 elimination required for the oxidation of chromate esters. This complex and its analogues have tetrahedral geometry at chromium, as established by X-ray crystallography of its analogues.[5][6]

Quick facts Names, Identifiers ...
tert-Butyl chromate
Names
IUPAC name
tert-Butyl chromate
Other names
Di-tert-butyl ester of chromic acid; Bis(tert-butyl)chromate
Identifiers
3D model (JSmol)
ChemSpider
RTECS number
  • GB2900000
  • InChI=1S/2C4H9O.Cr.2O/c2*1-4(2,3)5;;;/h2*1-3H3;;;/q2*-1;+2;;
    Key: PNWJTIFZRHJYLK-UHFFFAOYSA-N
  • InChI=1/2C4H9O.Cr.2O/c2*1-4(2,3)5;;;/h2*1-3H3;;;/q2*-1;+2;;/rC8H18CrO4/c1-7(2,3)12-9(10,11)13-8(4,5)6/h1-6H3
    Key: PNWJTIFZRHJYLK-PZTLRDNSAU
  • O([Cr](OC(C)(C)C)(=O)=O)C(C)(C)C
Properties
[(CH3)3CO]2CrO2
Molar mass 230.3 g/mol[1]
Appearance red oil
Melting point −2.8 °C (27.0 °F; 270.3 K)[2]
Miscible[2]
Hazards
NIOSH (US health exposure limits):
PEL (Permissible)
 TWA 0.005 mg CrO3/m3 [skin][1]
REL (Recommended)
 Ca TWA 0.001 mg Cr(VI)/m3[1]
IDLH (Immediate danger)
 Ca [15 mg/m3 {as Cr(VI)}][1]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Preparation

It can be prepared from tert-butyl alcohol and chromium trioxide or chromyl chloride.[3]

Applications

It is used as a precursor to chromium-based catalysts, such as the Phillips catalyst, which are employed for the polymerization of ethylene.[7]

Safety

Like other forms of hexavalent chromium, di-tert-butyl chromate is classified as a potential carcinogen by the United States National Institute for Occupational Safety and Health.[1][2]

References

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