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Alkyl Halide Reactivities.pdf

Abstract

Energetic analysis of compounds with similar reactive groups and divergent alkyl chains yields minimal information; thus, analysis of structure is best achieved by partaking by reactions. This can occur with as an SN2 reaction a strong nucleophile such as the iodide ion, which in the case of the Sodium iodide in acetone test dehalogenates the alkyl halide with greater efficiency when the reaction is not disrupted by stearic hindrance, yielding an iodionated alkyl product with a sodium halide precipitate, insoluble in the acetone.

Results

Discussion:

The SN2 reaction of NaI with 2-bromobutane took 17.5 minutes, due to stearic hindrance due to the secondary nature of the halide group. The stabilization of carbocation formation favors the formation of silver halide precipitate, as can be seen by the negative correlation between substitution and elapsed time for precipitate formation; apparently more so with AgBr than AgCl in acetone, as seen by 2-bromobutane reacting with AgNO3 and forming precipitate within 3.75 minutes, as opposed to 2-chlorobutane, which formed precipitate after 18 minutes.

2-chlorobutane formed silver chloride, which was likely partially protonated by the protic polar solvent and thus soluble, causing the appearance of solute to only appear after 18 minutes.

Iodide proves to be a good nucleophile, with the lack of steric hinderance favoring reaction with NaI with 1-bromobutane, which formed precipitate after 7.25 minutes, than with benzyl chloride, which took 11.75 minutes. For the AgNO3, Benzyl chloride formed AgCl after 6.75 minutes, but SN1 reactions do not occur with a primary alkyl halide because SN1 and E1

reactions require formation of a carbocation, the primary form of which is not very stable at all, thus it took 22 minutes to form a precipitate with 2-bromobutane, which did not as eaily form sufficient resonance structure.

The iodide nucleophile attacked both the benzylic and aryl halides with similar ease, in both cases after about 6 minutes for bromobenzene and 6.75 minutes for benzyl chloride. It is possible that the product of the formation of a stable benzylic carbocation was precipitated in ethanol from benzyl chloride after almost 12 minutes, but it was impossible for the aryl halide.