Master Organic Chemistry Reaction Guide

Elimination (E2) of alkyl halides to give alkenes

Description: Addition of strong base to an alkyl halide results in elimination to form a new C–C π bond.

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Real-Life Examples:

Org. Synth. 1931, 11, 1

DOI Link:10.15227/orgsyn.011.0001

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Org. Synth. 1943, 23, 45

Link: 10.15227/orgsyn.023.0045

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Org. Synth. 1958, 38, 47

DOI Link: 10.15227/orgsyn.038.0047

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Org. Synth. 1967, 47, 31

DOI Link: 10.15227/orgsyn.047.0031

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Comments

Comment section

5 thoughts on “Elimination (E2) of alkyl halides to give alkenes

    1. the reaction is 100 percent anti and the halide ion and the hudrogen atom that is polarised by the strong base shouid be diametrically opposite and the molecules periplaner . it seems to be a reaction of two steps bt is single step reaction

  1. Question: if isobutyl bromide is treated with -OH and H2O would this result in an E2 and SN2 reaction? I’m assuming that even though H2O is a polar protic solvent and -OH is a strong nucleophile the H2O would not affect -OH since it is -OH’s conj. acid. I’m thinking in this case with no heat added you would observe a competition between the -OH anion either deprotonating the single H from the beta carbon acting as a Lewis Base or a substitution resulting in an attack at the alpha carbon and replacement of Br with -OH? I guess seeing both -OH and H2O threw me off.

    1. Usually treatment with a bulky base will do the job. The classic example is t-BuO(-). In some cases tBuO(-) will also do the SN2 reaction (especially with unhindered primary alkyl halides like CH3CH2Br or CH3CH2CH2Br). Another option is a weak amine base like pyridine, triethylamine, or even (if your course covers it) DBU.

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