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The catalytic dehydrog enation of isomeric isopentenes. Part 3. The catalytic conversions of isopentenes in relation to their structure

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Summary

  1. 1.

    The catalytic conversion of the isopentenes takes place in two reactions, isomerization and dehydrogenation. Depending on the degree of conversion, the isomeric isopentenes are arranged in the following series: 3-methylbutene-1 >2-methylbutene-1 > 2-methylbutene-2.

  2. 2.

    Of the three isomeric isopentenes the most stable structure is that of 2-methylbutene-2, where breakdown occurs at the multiple bond, and the least stable is 3-methylbutene-1, breakdown occurring in the saturated portion of the molecule. With respect to the rate of isomerization, the isomets 3-methylbutene-1, 2-methylbutene-1 and 2-methylbutene-2 have the relative values 2.6 ∶ 1.73 ∶ 1, respectively.

  3. 3.

    2-methylbutene-2 is dehydrogenated at a greater rate than the other two isomers, 2-methylbutene-1 and 3-methylbutene-1, where rate constants are in the ratio 1.44∶ 1.15 ∶1.0. Activation energy of the dehydrogenation reaction is similar in all cases, and amounts to approximately 21–22 kcal/mole.

  4. 4.

    At temperatures between 580° and 620° the yield of isoprene amounts to 25–41% on the basis of the isopentenes supplied, and to 91–84% on the basis of the isopentenes consumed.

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Literature cited

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Bogdanova, O.K., Shcheglova, A.P. & Balandin, A.A. The catalytic dehydrog enation of isomeric isopentenes. Part 3. The catalytic conversions of isopentenes in relation to their structure. Russ Chem Bull 12, 1111–1114 (1963). https://doi.org/10.1007/BF00849666

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Keywords

  • Activation Energy
  • Dehydrogenation
  • Stable Structure
  • Isoprene
  • Great Rate