Isopropyl Bromide(C3H7Br): Properties And Preparation

Isopropyl bromide also referred to as 2-Bromopropane or 2-propyl bromide, is the halogenated hydrocarbon with the formula CH3CHBrCH3. It is a colorless liquid, insoluble in water but soluble in ethanol and ether. T is used for introducing the isopropyl functional group in organic synthesis. 2-Bromopropane is prepared by heating Isopropanol with hydrobromic acid.

Properties Isopropyl Bromide

Chemical FormulaC3H7Br
Molar Mass122.993 g/mol
AppearanceColorless liquid
Density1.31 g/ml
Melting point-89.0 oC (-138.1oF, 184.2K)
Boiling Point51-61oC (138 to 142oF, 322 to 334K)
Heat capacity135.6 J/mol
Solubility in water3.2g/l (at 20oC)
Related alkanesBromoethane 1-Bromopropane 1-Bromobutane 2-Bromobutane  

Preparation Of Isopropyl Bromide

  • 40 grams of isopropyl alcohol are mixed with 460 grams of concentrated hydrobromic acid in a 500 ml distilling flask, fitted with an efficient condenser and a receiver.
  • The flask is gently heated and the isopropyl bromide is slowly distilled few drops per minute until about half of the liquid has passed over.
  • The lower isopropyl bromide layer is separated.
  • Redistillation of the aqueous layer yields additional 7 grams of the crude isopropyl bromide.
  • The residue in the distillation flask may be mixed with the aqueous layer of the first distillate, 40 grams of isopropyl alcohol are added and the slow distillation repeated.
  • The yield of crude isopropyl bromide in the second distillation is only slightly less than that obtained in the original preparation.
  • Subsequently, most of the residual hydrobromic acid may be recovered by distillation as the constant boiling point acid (126oC).
  • The obtained crude isopropyl bromide is washed with an equal volume of concentrated hydrochloric acid in order to remove unreacted isopropyl alcohol, then, water, 5% sodium bicarbonate solution and dried with anhydrous calcium chloride.
  • Isopropyl bromide is purified by distillation. The fraction passing over 59oC is collected yielding 66 grams of pure isopropyl bromide.