Isobutene

Isobutene and isobutylene are other names used for the organic compound with the IUPAC name 2-methylpropene. 2-methylpropene is one of the four structural isomers of butene and it exists as a highly flammable, colourless gas at standard temperature and pressure. Isobutene can be converted into fuel additives that increase the octane rating and prevent engine knocking.
Addition polymerization of isobutene results in polyisobutene (PIB) a rubbery substance which is used in the manufacture of tires, adhesives, ball bladders, caulks and sealants, cling film, rubber modification, fuel additives, and chewing gum.

Researchers at the Department of Energy's Pacific Northwest National Laboratory and at Washington State University have developed a new catalyst material composed of zinc oxide and zirconium oxide that will convert bio-ethanol into isobutene in one production step.
If the catalyst was composed only of zinc oxide, the ethanol was mostly converted into acetone (the chemical used in nail polish remover).
If the catalyst was composed only of zirconium oxide, the ethanol was mostly converted into ethylene (the chemical made by plants that ripens fruit).
When the catalyst is composed of a 1:10 ratio of zinc oxide to zirconium oxide, 83% of the ethanol was converted into isobutene.

Reference
Junming Sun, Kake Zhu, Feng Gao, Chongmin Wang, Jun Liu, Charles H. F. Peden, Yong Wang. Direct Conversion of Bio-ethanol to Isobutene on Nanosized ZnxZryOzMixed Oxides with Balanced Acid–Base Sites. Journal of the American Chemical Society, 2011; 133 (29): 11096 DOI: 10.1021/ja204235v

Further Reading
Naming Carbon Compounds
Structural Isomers of Alkenes
Ideal Gas Law
Polymers and Polymerization
Fuel Definitions
Energy Profiles

Study Questions

1. Give the molecular formula and structural formula for 2-methylpropene.
2. Draw the structural formula for all four structural isomers of butene.
3. Write an equation to represent the polymerization of 2-methylpropene to polyisobutene.
4. Use diagrams to show why the polymerization reaction above is considered to be an addition polymerization reaction.
5. On the diagram produced in response to question 4, clearly label the monomer and polymer compounds.
   
6. Give likely formulae for both zinc oxide and zirconium oxide.
7. Give the IUPAC name, the molecular formula and the structural formula, for each of the following:
   • isobutene
     
   • acetone
   • ethylene
8. Write equations for each of the following catalyzed reactions:
   • the conversion of ethanol into acetone
     
   • the conversion of ethanol into ethylene
9. Which of the following compounds could undergo addition polymerization? Justify your answer.
   
   • acetone
   • ethylene
10. Name the products of any successful addition polymerization in question 8.