Lithium borohydride

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Lithium borohydride
Names
IUPAC name
Lithium tetrahydridoborate
Other names
Lithium boron hydride
Lithium hydroborate
Lithium tetrahydroborate
Properties
LiBH4
Molar mass 21.784 g/mol
Appearance White or grayish solid
Odor Odorless
Density 0.666 g/cm3 (20 °C)
Melting point 268 °C (514 °F; 541 K)
Boiling point 380 °C (716 °F; 653 K) (decomposes)
Reacts
Solubility Reacts with alcohols, carboxylic acids, aldehydes, halocarbons, ketones
Soluble in ethers
Insoluble in cyclohexane, heptane, hexane, pentane, toluene, xylene
Solubility in 1,4-Dioxane 0.3 g/100 ml (18 °C)
Solubility in diethyl ether 1.32 g/100 ml (0 °C)
3.04973 g/100 ml (25 °C)
6.62228 g/100 ml (34 °C)
Solubility in dimethoxyethane 4.13892 g/100 ml (0 °C)
4.5746 g/100 ml (75 °C)
Solubility in dimethyl ether 1.6 g/100 ml (-45.2 °C)
Solubility in tetrahydrofuran 24.8989 g/100 ml (25 °C)
Vapor pressure ~0 mmHg
Thermochemistry
75.7 J·mol-1K-1
-198.83 kJ/mol
Hazards
Safety data sheet Sigma-Aldrich
Lethal dose or concentration (LD, LC):
87.8 mg/kg (mouse, oral)
Related compounds
Related compounds
Sodium borohydride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Lithium borohydride (LiBH4) is a chemical compound widely used in organic synthesis as a reducing agent, often for esters.

Properties

Chemical

Lithium borohydride reacts with water to release hydrogen gas.

LiBH4 + 4 H2O → LiOH + B(OH)3 + 4 H2

Physical

Lithium borohydride is a white solid, which reacts with water and alcohols, but it's soluble in ethers.

Lithium borohydride has the highest energy density of all known chemical energy carriers, with a value of 65.2 MJ/kg or 43.4 MJ/l, higher than gasoline.

Availability

It is sold by chemical suppliers.

Preparation

Lithium borohydride may be prepared by the metathesis reaction, which occurs upon ball-milling the more commonly available sodium borohydride, and lithium bromide:[1]

NaBH4 + LiBr → NaBr + LiBH4

Alternatively it may be synthesized by treating lithium hydride with boron trifluoride in diethyl ether:[2]

BF3 + 4 LiH → LiBH4 + 3 LiF

Projects

  • Reducing agent
  • Fuel cells

Handling

Safety

Lithium borohydride reacts with water and moisture, and may ignite in open air.

Storage

Lithium borohydride should be kept in closed bottles, under inert gas.

Disposal

Can be safely neutralized by adding it slowly in a large volume of alcohol or water.

References

  1. Peter Rittmeyer, Ulrich Wietelmann “Hydrides” in Ullmann's Encyclopedia of Industrial Chemistry, 2002, Wiley-VCH, Weinheim.
  2. Brauer, Georg (1963). Handbook of Preparative Inorganic Chemistry Vol. 1, 2nd Ed. Newyork: Academic Press. p. 775. ISBN 978-0121266011. 

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