Trimethylborane

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Trimethylborane
Names
Preferred IUPAC name
Trimethylborane[1]
Other names
Trimethylborine
Trimethylboron
Identifiers
3D model (
JSmol
)
ChemSpider
ECHA InfoCard
 100.008.926 Edit this at Wikidata
EC Number
  • 209-816-3
  • InChI=1S/C3H9B/c1-4(2)3/h1-3H3 checkY
    Key: WXRGABKACDFXMG-UHFFFAOYSA-N checkY
  • CB(C)C
Properties
C3H9B
Molar mass 55.92 g/mol
Appearance Colorless gas or liquid
Density 0.625 g/cm3 at −100 °C[3]
Melting point −161.5 °C (−258.7 °F; 111.6 K)
Boiling point −20.2 °C (−4.4 °F; 253.0 K)
Slight, highly reactive
Structure
Δ
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
 Spontaneously flammable in air; causes burns
GHS labelling:
GHS02: Flammable GHS04: Compressed Gas GHS05: Corrosive
Danger
H220, H250, H280, H314
P210, P222, P260, P264, P280, P301+P330+P331, P302+P334, P303+P361+P353, P304+P340, P305+P351+P338, P310, P321, P363, P370+P378, P377, P381, P403, P405, P410+P403, P422, P501
Flash point Not applicable, pyrophoric gas
−40 °C (−40 °F; 233 K)[4]
Safety data sheet (SDS) MSDS from Voltaix
Related compounds
Related compounds
  • Methylborane
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Trimethylborane (TMB) is a toxic,

methyl
).

Properties

As a liquid it is colourless. The strongest line in the

infrared spectrum
is at 1330 cm−1 followed by lines at 3010 cm−1 and 1185 cm−1.

Its melting point is −161.5 °C, and its boiling point is −20.2 °C.

Vapour pressure is given by log P = 6.1385 + 1.75 log T − 1393.3/T − 0.007735 T, where T is temperature in kelvins.[5] Molecular weight is 55.914. The heat of vapourisation is 25.6 kJ/mol.[4]

Preparation

Trimethylborane was first described in 1862 by

methyl magnesium iodide.[10]

Reactions

Trimethylborane spontaneously ignites in air if the concentration is high enough. It burns with a green flame producing soot.[11] Slower oxidation with oxygen in a solvent or in the gas phase can produce dimethyltrioxadiboralane, which contains a ring of two boron and three oxygen atoms. However the major product is dimethylborylmethylperoxide, which rapidly decomposes to dimethoxymethylborane.[12]

Trimethylborane is a strong

Lewis acid. B(CH3)3 can form an adduct with ammonia: (NH3):B(CH3)3.[13] as well as other Lewis bases. The Lewis acid properties of B(CH3)3 have been analyzed by the ECW model yielding EA= 2.90 and CA= 3.60. When trimethylborane forms an adduct with trimethylamine
, steric repulsion between the methyl groups on the B and N results. The ECW model can provide a measure of this steric effect.

Trimethylborane reacts with water and chlorine at room temperature. It also reacts with grease but not with

teflon or glass.[5]

Trimethylborane reacts with

dimethyldiborane
: (CH3)BH2.BH3 and (CH3)2BH.BH3.

It reacts as a gas with trimethylphosphine to form a solid Lewis salt with a heat of formation of −41 kcal per mol. This adduct has a heat of sublimation of −24.6 kcal/mol. No reaction occurs with trimethylarsine or trimethylstibine.[10]

Methyl lithium reacting with the Trimethylborane produces a tetramethylborate salt: LiB(CH3)4.[14] The tetramethylborate ion has a negative charge and is isoelectronic with neopentane, tetramethylsilane, and the tetramethylammonium cation.

Use

Trimethylborane has been used as a neutron counter.

chemical vapour deposition
where boron and carbon need to be deposited together.

References

  1. ISBN 978-0-85404-182-4
    .. p. 974.
  2. ISBN 978-3-540-66774-2
    .
  3. ^ See MSDS
  4. ^ a b "Trimethylborane" (2009) at the Online Chemical Dictionary. Archived 2012-03-16 at the Wayback Machine.
  5. ^ a b c Rees, William S. Jr.; et al. (1990). Ginsberg, Alvin P. (ed.). Trimethylborane. Inorganic Syntheses. Vol. 27. p. 339.
  6. doi:10.1002/jlac.18621240102
    .
  7. PMID 21113558
    .
  8. doi:10.1002/cber.19210540321
    .
  9. doi:10.1080/00945717308057281
    .
  10. ^
    Texas Tech. Archived from the original
    (PDF) on 2011-08-15. Retrieved 2010-09-23.
  11. ISBN 978-0-8206-0364-3
    .
  12. doi:10.1016/s0022-328x(00)82027-6
    .
  13. ^ a b Ross, Gaylon S.; et al. (2 October 1961). "Preparation of High Purity Trimethylborane" (PDF). Journal of Research of the National Bureau of Standards Section A. 66 (1). Archived from the original (PDF) on 19 October 2011. Retrieved 22 September 2010.
  14. ^ Georg Wittig in 1958
  15. ISSN 0034-6748
    .
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