Iso Propyl bromide

Substitution can take place by the S l or the 8 2 mechanism elimination by El or E2 How can we predict whether substitution or elimination will be the principal reac tion observed with a particular combination of reactants The two most important fac tors are the structure of the alkyl halide and the basicity of the anion It is useful to approach the question from the premise that the characteristic reaction of alkyl halides with Lewis bases is elimination and that substitution predominates only under certain special circumstances In a typical reaction a typical secondary alkyl halide such as iso propyl bromide reacts with a typical Lewis base such as sodium ethoxide mainly by elimination... 

FIGURE 8 11 When a Lewis base reacts with an alkyl halide either substitution or elimination can occur Sub stitution (Sn2) occurs when the Lewis base acts as a nu cleophile and attacks carbon to displace bromide Elimi nation (E2) occurs when the Lewis base abstracts a pro ton from the p carbon The alkyl halide shown is iso propyl bromide and elimi nation (E2) predominates over substitution with alkox ide bases... 

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

Sulfuric acid and isoamylene under suitable conditions yield diisoamylene also. This polymerization reaction is used commercially in the formation of synthetic rubber from the octadiens. The specific action of the particular catalyst employed is shown also by the fact that iso-propyl bromide dissociated at the temperature of boiling amylene in the presence of asbestos, while the n-bromide did not. [D. Konowalow, Ber. 18, 2808 (1885).]... 

Grignard reagent from -amyl bromide, 16, 41 from benzyl chloride, 10, 4 17, 89 from bromomesitylene, 11, 66 from a-bromonaphthalene, 11, 80 from 2-bromopentane, 11,84 from -butyl bromide, 15,11 from ethyl bromide, 11, 98 17, 48 from iso propyl bromide, IS, 48... 

Other iV-alkyl-m-toluidines may be prepared by practically the same procedure. The submitters report that -propyl, iso-propyl, and w-butyl derivatives are obtained readily from m-toluidine and the appropriate alkyl iodides (rather than the bromides). In these cases the alkylation is effected by placing the sealed bottle in a beaker of water which is wanned gradually to 70-80° and kept in a warm place until the reaction is completed usually several days are required. 

Elimination from iso-Propyl, sec.-Butyl, 2 n-Amyl, and 3 n-Amyl Bromides in Acidic and Alkaline Alcoholic Media. J. chem. Soc. (London) 1948, 2065-... 

Bei der Reaktion von Diisopropylamin mit l-Chlor-2,4-dinitro-benzol in Benzol bei 60° entsteht das erwartete N,N-Diisopropyl-2,4-dinitro-anilin nur in sehr geringer Ausbeute als Hauptprodukt entsteht das nur eine Isopropyl-Gruppe enthaltende 2,4-Dinitro-N-iso-propyl-anilin neben einer geringeren Menge an 2,4-Dinitro-N propyl-anilin1. Ahnliche Er-gebnisse erhalt man mit dem entsprechenden Aryl-fluorid und -bromid sowie bei Durch-fiihrung der Reaktion in Methanol oder Dimethyl-sulfoxid. 

An interesting method for the introduction of substituents into the 2-position of the quinuclidine ring starting from 3-substituted A2-dehydroquinuclidines (126) has been described.47 By the reaction of methyl J2-dehydroquinuclidine-3-carboxylate (130) with iso-propylmagnesium bromide, 1,4-addition with formation of 2-iso-propyl-3-methoxycarbonylquinuclidine (131) took place instead of a sterically hindered Grignard reaction at the alkoxycarbonyl group. 

Dialkylation of malonic ester proceeds in most cases almost as readily as monoalkylation. Diethyl ethylmalonate is alkylated equally well by s-octyl and n-butyl halides. Di-n-propylmalonic ester is prepared in one step from malonic ester and n-propyl bromide. Methylmalonic ester is alkylated by /3-phenylethyl bromide, and even a-naphthyl-malonic ester may be further alkylated by n-alkyl iodides. Difficulty is encountered, however, in introducing two s alkyl groups into malonic ester. A 23% yield of diisopropylmalonic ester is obtained from iso-ptopylmalonic ester, sodium triphenylmethide, and isopropyl iodide. ... 

Cymene. i-Methyl 4-Iso-propyl Benzene.—Cymene, the only other isomeric hydrocarbon of the composition C10H14, which we shall consider, is shown to be i-methyl 4-iso-propyl benzene, by its synthesis from para-brom toluene and isopropyl bromide. 

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