W-Propyl bromide

The fact that n- butyl benzene call be prepared in reasonable yield by the action of sodium upon a mixture of bromobenzene and w-butyl bromide can be partly explained on the assumption that n- butyl bromide reacts with phenyl-sodium more rapidly than does bromobeuzene. It is interesting to note that n-butylbenzene can be prepared either from benzylsodium and w-propyl bromide or from phenylsodium and n-butyl bromide (Section VI,29). 

M-Butylbenzene has been prepared by the action of sodium (a) on benzyl chloride or bromide and w-propyl bromide without diluents,1 or (b) on n butyl bromide and bromobenzene without a solvent2 or in benzene 3 by a Clemmensen reduction of ra-butyr-ophenone 4 and by the action of benzylmagnesium chloride on M-propyl />-toluenesulfonate.5 Other procedures do not appear to be of preparative value. 

The competition between elimination and substitution channels when an alkyl halide is allowed to react with a nucleophile in the gas phase is a difficult problem to tackle, since in most gas-phase experiments only the ionic products of reaction are monitored (a few exceptions are reported below). Thus, for example, when w-propyl bromide is allowed to react with methoxide ion in the gas phase, the bromide ion produced can arise either by elimination (a) or by substitution (b) and the two pathways cannot be distinguished from the ions alone (Scheme 34). In this specific case it was possible to establish that the reaction follows exclusively the elimination channel through collection and analysis of the neutral products246. The experiments were performed on a FA apparatus configured with a novel cold finger trap coupled to a GC/MS system. Material collected by the trap was separated by capillary gas chromatography and the individual components identified by their retention times and El mass spectra246. 

Ionic addition yields isopropyl bromide because a secondary cation is formed faster than a primary. Free-radical addition yields w-propyl bromide because a secondary free radical is formed faster than a primary. Examination of many cases of anti-Markovnikov addition shows that orientation is governed by the ease of formation of free radicals, which follows the sequence 3° > 2 > T. 

Using similar procedures, the following can be prepared in the yields indicated ec.-butyl bromide, b.p. 90-93°, 80 per cent w-propyl bromide, b.p. 70-73°, 95 per cent im-propyl bromide, b.p. 60-63°, 68 per cent. 

To this solution of sodium sulfide is added dropwise with stirring 246 g. (2 moles) of w-propyl bromide (Org. Syn. 13, 21). After all the bromide has been added the flask is heated on a steam cone for eight hours (Note 2), during which time the mix-... 

The formation of alkylbenzenes, largely free from unsaturated compounds, provides another interesting application of organosodium compounds. Thus pure -butylbenzene is readily obtained in good yield from benzyl-sodium and w-propyl bromide. Benzyl-sodium is conveniently prepared by first forming phenyl-sodium by reaction between sodium and chlorobenzene in a toluene medium, followed by heating the toluene suspension of the phenyl-sodium at 105° for about 35 minutes ... 

The etherification of 4-mercaptoacetanilide with w-propyl bromide gives rise to the formation of 2-nitro-4 (propylthio) acetanilide with the elimination of one mole of HBr. The resulting product upon hydrolysis converts it to an amine, reduction with SnCl2 to a diamine, and finally interaction with S-methyl thiourea affords eyelization to yield carbamie aeid [5-(propylthio)-IH benzimidazol-2-amino]. This upon acetylation with methyl ehloroformate affords the offieial eompound albendazole. 

Tri-n-propyl-p-tolylphosphonium bromide, (C3H7)3C7H7.PBr, IS obtained only with difficulty when p-tolyldi-n-propylphosphine is refluxed with w-propyl bromide in ether solution. It forms well-developed, hygroscopic needles, M.pt. 125 5° C. 

The compound shown below is a constitutent of the pheromone of the codling moth. It has been synthesized using w-propyl bromide, propyne, 1-pentyne, ethylene oxide, and CO2 as the source of the carbon atoms. Devise a route for such a synthesis. Hint Extensive use of the chemistry of organocopper reagents is the basis for the existing S)mthesis. 

The reactivity is further influenced by the branching of the carbon chain and by the possible presence of a double bond and position of a second halogen atom. Among the tested monovalent and divalent halo compounds (5), methyl iodide, allyl bromide, benzyl bromide, and methylene iodide were found most reactive, a medium reactivity was observed for penta-methylene bromide, ethyl bromide, w-propyl bromide, n-butyl bromide, and w-amyl bromide, while ethylene bromide and isobutyl bromide reacted most slowly. 

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