EXPT 9 Dehydration

The more stable alkene is generally the alkene with

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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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This note was uploaded on 12/15/2012 for the course CHE 301 taught by Professor Lucy during the Spring '12 term at VCU.

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