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Properties of substance:

potassium borohydride

Synonyms:

potassium tetrahydroborate

Group of substances:

inorganic

Physical appearance:

white cubic crystals

Empirical formula (Hill's system for organic substances):

H4BK

Structural formula as text:

KBH4

Molar/atomic mass: 53.94

Melting point (°C):

585

Decomposition temperature (°C):

584

Solubility (g/100 g of solvent):

1,4-dioxane: practically insoluble [Ref.]
2-butoxyethanol: 1.43 (25°C) [Ref.]
3-pentanol: 0.66 (25°C) [Ref.]
acetonitrile: 0.29 [Ref.]
ammonia liquid : 20 (-30°C) [Ref.]
benzene: practically insoluble [Ref.]
diethanolamine: 0.71 (25°C) [Ref.]
diethyl ether: insoluble [Ref.]
diglyme: insoluble [Ref.]
dimethylformamide: 1.2 (25°C) [Ref.]
dimethylsulfoxide: 7.6 [Ref.]
ethanol 95%: 0.25 (25°C) [Ref.]
ethanolamine: 1.52 (25°C) [Ref.]
ethylene glycol monomethyl ether: 0.04 (25°C) [Ref.]
ethylenediamine: 3.9 (75°C) [Ref.]
hexane: practically insoluble [Ref.]
isopropylamine: insoluble [Ref.]
isopropylamine: practically insoluble [Ref.]
methanol: 0.7 (20°C) [Ref.]
methanol 20%: 13 (20°C) [Ref.]
methanol 80%: 1.9 (20°C) [Ref.]
morpholine: 0.04 (25°C) [Ref.]
n-butylamine: insoluble [Ref.]
n-butylamine: 0.08 (25°C) [Ref.]
pyridine: insoluble [Ref.]
tetraglyme: 0.07 [Ref.]
tetrahydrofuran: 0.23 [Ref.]
triethylamine: insoluble [Ref.]
water: 15.3 (0°C) [Ref.]
water: 17.9 (7.3°C) [Ref.]
water: 22.6 (20.5°C) [Ref.]
water: 24 (25°C) [Ref.]
water: 25.8 (29.2°C) [Ref.]
water: 29 (37.5°C) [Ref.]
water: 37.9 (60.5°C) [Ref.]
water: 45 (84.9°C) [Ref.]

Density:

1.17 (20°C, g/cm3)

Synthesis 1:

Reference: Banus, M.D., Bragdon, R.W., Hinckley, A.A. (1954). Potassium, Rubidium and Cesium Borohydrides / Journal of the American Chemical Society. - 1954. - Vol. 76, No. 14 pp. 3848 [doi: 10.1021/ja01643a077]

NaBH4 + KOH → KBH4 + NaOH

A solution of 74.2 g. of 94.7% sodium borohydride in 130 cc. of distilled water was added to a stirred solution of 133.2 g. of potassium hydroxide (85% assay) in 110 cc. of water. The resulting thick slurry was filtered through a medium-porosity, sintered glass disc under nitrogen pressure. The precipitate was washed with three 100-cc. portions of ice-cold, 95% ethanol. The product was then dried in a vacuum oven at 80° for three hours; 75.5 grams of potassium borohydride was obtained, representing a yield of 75.5%.

Anal. Calcd. for KBH4: K, 72.48; B, 20.06; H, 7.47. Found: K, 73.3; B, 19.8; H, 7.25.

Standard molar enthalpy (heat) of formation ΔfH0 (298.15 K, kJ/mol):

-227 (s)

Standard molar entropy S0 (298.15 K, J/(mol·K)):

106.5 (s)

Molar heat capacity at constant pressure Cp (298.15 K, J/(mol·K)):

96.2 (s)

References:

  1. Armarego W. L. F. Purification of Laboratory Chemicals. - 7ed. - 2013. - pp. 599
  2. Progress in inorganic chemistry. - Vol. 11. - John Wiley & Sons, 1970. - pp. 112, 136-139
  3. Ефимов А.И. и др. Свойства неорганических соединений. Справочник. - Л.: Химия, 1983. - pp. 126-127 [Russian]
  4. Жигач А.Ф., Стасиневич Д.С. Химия гидридов. - Л.: Химия, 1969. - pp. 427-433 [Russian]
  5. Корольченко А.Я., Корольченко Д.А. Пожаровзрывоопасность веществ и материалов и средства их тушения. - 2 изд, Ч.1. - М.: Ассоциация Пожнаука, 2004. - pp. 597 [Russian]
  6. Краткая химическая энциклопедия. - Т. 2: Ж-Малоновый эфир. - М.: Советская энциклопедия, 1963. - pp. 354 [Russian]
  7. Некрасов Б.В. Основы общей химии. - Т.2. - М.: Химия, 1973. - pp. 26 [Russian]
  8. Общая органическая химия. - Т. 6, под ред. Бартона Д. и Оллиса В.Д. - М.: Химия, 1984. - pp. 245 [Russian]
  9. Хайош А. Комплексные гидриды в органической химии. - Л.: Химия, 1971. - pp. 66-68 [Russian]
  10. Химическая энциклопедия. - Т. 1. - М.: Советская энциклопедия, 1988. - pp. 308 [Russian]

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    © Collected Ruslan Anatolievich Kiper, burewestnik@mail.ru