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Unformatted text preview: le alkene is generally the alkene with the more
substituted double bond. This is known as Zaitsev elimination. Of course, if two or more alkenes
can be formed, usually all products will be formed. This can lead to separation problems, since
all of the alkenes formed in a reaction will generally have boiling points or melting points fairly
close to one another as well as similar solubilities in common solvents. Because of these
separation problems, it is often necessary to resort to gas chromatography or liquid
chromatography to separate the products. An example of an elimination which gives a product
mixture is the conversion of 2-methyl-2-butanol into 2-methyl-1-butene and 2-methyl-2-butene
(Eq. 2). OH conc. H3PO 4 + (Eq. 2) heat
major minor Since the reaction involves a carbocation intermediate, there is another consideration which must
be taken into account, the possibility of rearrangement of the initial carbocation to a more stable
carbocation which then leads to a different product. For example, treatment of 3,3-dimethyl-1butanol would not give 3,3-dimethyl-1-butene, but would instead lead primarily to 2,3-dimethyl2-butene via rearrangement of the initial carbocation to a tertiary carbocation by a series of 1,2group migrations (Eq. 3). HO conc. H3PO 4...
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