Dibromo butane

Insoluble in water, soluble in organic solvents b.p. — 15°C. Prepared by treating 1,4-dibromo-butane with metallic sodium. Reduced to n-butane by hydrogen at 200" C in presence of nickel catalysts. 

Dibromobutane from 1 4 butanediol). In a 500 ml. threenecked flask fltted with a stirrer, reflux condenser and dropping funnel, place 154 g. (105 ml.) of 48 per cent, hydrobromic acid. Cool the flask in an ice bath. Add slowly, with stirring, 130 g. (71 ml.) of concentrated sulphuric acid. To the resulting ice-cold solution add 30 g. of redistilled 1 4-butanediol dropwise. Leave the reaction mixture to stand for 24 hours heat for 3 hours on a steam bath. The reaction mixture separates into two layers. Separate the lower layer, wash it successively with water, 10 per cent, sodium carbonate solution and water, and then dry with anhydrous magnesium sulphate. Distil and collect the 1 4-dibromo-butane at 83-84°/12 mm. The yield is 55 g. 

In the presence of catalysts, trichloroethylene is readily chlorinated to pentachloro- and hexachloroethane. Bromination yields l,2-dibromo-l,l,2-trichloroethane [13749-38-7]. The analogous iodine derivative has not been reported. Fluorination with hydrogen fluoride in the presence of antimony trifluoride produces 2-chloro-l,l,l-trifluoroethane [75-88-7] (8). Elemental fluorine gives a mixture of chlorofluoro derivatives of ethane, ethylene, and butane. 

The synthesis of 1-ethoxy-1-butjme has been reported previously, but the preparations have required multistep sequences. Two of the procedures use 1,2-dibromo-l-ethoxy butane which is dehydrohalogenated in two successive steps, first by an amine base and then by either powdered potassium hydroxide or sodium amide no yields are given. The... 

Thus, (Z)-but-2-ene will react to give 2,3-dibromo-butane as a pair of enantiomers, R,R and S,S, a result of the anti addition. A racemic product will thus be formed, because there is equal probability of... 

Tertiary alkyl radical Tertiary alkyl radical 1,5-Dibromo-3,3,4,4-tetramethyl butane... 

Halogenation of double bonds is stereospecific. A reaction is stereospecific when a particular stereoisomeric form of the starting material gives a specific stereoisomeric form of the product. For example, the halogenation of cis- and tra 5-2-butene produces a racemic mixture of 2,3-dibromo-butane and mc5o-2,3-dibromobutane, respectively. 

DBU (4.17 g, 27.4 mmol) was slowly added with stirring to a solution of 1,3-dibromo-l, l-difluoro-4-phenyl-butane (4, Ar = Ph 3.00 g, 9.15 mmol) in Et20 (15 mL) at a rate that maintained the temperature below 30 C. Solid DBU HBr salt formed during the addition. The resulting mixture was stirred for an additional 15 min. It was then diluted with EtzO (10 mL), and washed with 3 M HC1 (2 x 20 mL) to dissolve the salt. The Et,0 phase was separated and dried (CaCl2). Evaporation of the volatile material left a pale-yellow liquid yield 0.84g (55%) (E/Z) 9 1. 

Dibromo-l, 1,1 -trifluoro-2,2-bis(trifluoromethyl)butane (22) with potassium hydroxide provides 4.4,4-trifluoro-3.3-bis(trifluoromethyl)but-l-yne (23).9... 

Butane 2-Chlorn-l, 4-dibromo-1.1.2-triflnoro- ElOa. 46 ( loxicity)... 

Butane 1.2-Dibromo-hexafluoro-3-oxo- E10b2. 148 (Educl) Propanoyl Bromide 2-Bromo-lrifluoro-2-t ritluoi omcthyl-EI0b2. 149 (Educt ... 

Butane 2,2-Bis-[trifluoromctliyl]-3.4-dibromo-1.1,1-trifluoro- E10b2. 101 (F.duct)... 

Butane 2-Chloro-1.4-dibromo-l,l,2-triflxioro-4-trimethyIsilyl- EI0b2. 

Butane 1,3-Dibromo-l,l-difluoro-4-phenyl- EI0b2, 97 (Educt)... 

Preparation 349.—Dibromosuccinic Acid [2 3-Dibromo-butan-diacid],... 

Preparative Methods the title reagent is prepared by the treatment of (IR, 25)-(—)-norephedrine with 1,4-dibromo-butane and NaHCOs in toluene. This approach can be modified to form a wide variety of cyclic and acyclic tertiary amine derivatives. The enantiomeric reagent has also been formed from (+)-norephedrine. 

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