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ChemicalBook CAS DataBase List 1-Bromopropane
106-94-5

1-Bromopropane synthesis

11synthesis methods
1-Bromopropane can be synthesized by reacting n-propyl alcohol (n-propanol) with excess hydrobromic acid. Water formed as a by-product is quickly removed from the resulting crude product before purification to give the final product. A modification of this reaction procedure involves using bromine with a reducing agent such as sulfur, sulfur dioxide, phosphorus or sodium borohydride. The overall reaction with hydrobromic acid is depicted below.
n-C3H7OH + HBr => n-C3H7Br + H2O
The prefix n (or normal) refers to a “straight chain” hydrocarbon component as opposed to a branched hydrocarbon component, such as the isopropyl group in isopropyl alcohol (i-propyl alcohol or i-propanol) where the hydroxyl (−OH) group is attached to the middle carbon.
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Yield:106-94-5 97.8% ，75-26-3 1.57%

Reaction Conditions:

with hydrogen bromide;oxygen at 20 - 23; under 1551.49 - 1603.2 Torr; for 4.5 h;

Steps:

1

A laboratory-scale backpressure reactor was constructed using a heavy- walled, 60 psi (413.7 kPa) rated 500 rnL flask with threaded Teflon polymer coated connections to a 60 psi (413.7 kPa) rated condenser (50C coolant) and adapters with the vent gas connected to a back pressure regulator. An initial liquid volume of 178.70 g , (1.124 mol) NPB was added into the reactor. Hydrogen bromide gas was fed super- surface, through 0.5 inch (1.27 cm) Teflon polymer coated tubing increasing a rate of 0.67 g/min. for 3-4 minutes. Propene was fed through 0.25 inch (0.635 cm) PTFE tubing initially at approximately 205 mL/min though calibrated flow meters into a Fischer-Porter bottle. Oxygen-containing gas (air) (6 mL/min) was metered via computerized pump using No.14 Viton tubing into the Fischer-Porter bottle. The propene and air mixture was fed subsurface to the 500 mL flask during a 4.5 hour addition, during which HBr feed was maintained at approximately 0.67 gm/min. The hydrobromination was performed at 20- 23°C, 30-31 psi (206.8-213.7 kPa) with these pressures being maintained using a backpressure regulator. The liquid product was condensed as it was formed. The vent gas was scrubbed through water to remove HBr and the exit gas flow was measured intermittently with a gas (Bunte) buret. The calculated conversion to NPB, based on propene feed and hydrogen bromide exit gas amounts was 99.90 mole %. The crude EPO product contained 1.30 % dissolved HBr, and after washing with 87.26 g water and phase separation, an isolated yield of 250 g of propyl bromide in excess of the initial heel was obtained. Analysis of the vent gas showed 0.10% propene, 1.90 % propane and indicated sufficiently low flow of combustible organics so as to maintain below the flamability range of both propene and propane in air. Propane, an impurity in propene, is the predominant hydrocarbon vent gas under these experimental conditions (with 1-3% excess HBr flow in excess of stoichiometric amount necessary when measured at atomospheric pressure) and is unreactive to that it passes through the system as an inert flammable exit gas. GC analysis of the product indicated 97.80 % NPB, 1.57 % IPB, 0.20 % dibromopropane on a GC area percent basis. Typically, the exit gas analysis had a reaction completion of greater than 99.5 %. The reactor yield is limited by the selectivity for NPB, typically 96.0-98.4 %.

References:

WO2006/113307,2006,A1 Location in patent:Page/Page column 18; 19

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