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.
    
    
    

VMD for Fingerprinting

Forensic experts at the University of Abertay Dundee and the Scottish Police Services Authority (SPSA) are researching vacuum metal deposition (VMD) to recover fingerprint ridge detail and impressions from fabrics.

Vacuum metal deposition, VMD, is a common method of depositing a thin film on a substrate.
The source metal is evaporated in a vacuum which allows the vapor particles to travel directly to the target object, the substrate, where they condense back to the solid state. Evaporated materials deposit non-uniformly if the substrate has a rough surface, and, because the evaporated material attacks the substrate mostly from one direction, protruding features block the evaporated material from some areas which is called "shadowing" or " step coverage".

The Scottish scientists have been using gold and zinc in a VMD process to recover fingerprint marks on fabrics. The fabrics are placed in a vacuum chamber then gold is heated up to evaporate it. The gold particles spread out in a thin film over the fabric. Zinc is then heated up, and the zinc particles attach to the gold particles where there are no fingerprint residues. The fingerprint ridges show up as clear fabric, but where there are no fingerprint ridges the distinctive grey colour of the zinc metal is seen.

While only 20% of the public are classed as "good donors" for leaving fingerprints, the researchers have had great success in revealing the shape of a handprint on a number of fabric types. Handprints could help the police piece together a timeline of events which could be used to provide evidence in cases where someone was pushed, or grabbed, in a particular area of their clothing. For example, an impression of a palm print on the back of someone's shirt might indicate they were pushed off a balcony, rather than jumping.

Reference
Joanna Fraser, Keith Sturrock, Paul Deacon, Stephen Bleay, David H. Bremner. Visualisation of fingermarks and grab impressions on fabrics. Part 1: Gold/zinc vacuum metal deposition. Forensic Science International, 2010; DOI: 10.1016/j.forsciint.2010.11.003

Further Reading
Physical and Chemical Changes

Study Questions

1. What do Chemists mean when they refer to evaporation?
2. What do Chemists mean when they refer to condensation?
3. Are evaporation and condensation examples of chemical or physical changes? Explain your answer.
   
4. Write a chemical equation to represent the evaporation of solid gold as described above in the process of vacuum metal deposition.
5. Do you think the equation you wrote above is an example of an evaporation process? Explain your answer.
6. Write a chemical equation to describe the process of gold vapor condensing on a fabric as described in the process of vacuum metal deposition.
7. Give the name for the change of state being described in each of the following:
   
   • heating solid gold until it forms a liquid
   • heating solid gold in a vacuum so that it forms a vapor
   • cooling gold vapor in a vacuum so that if forms solid gold
   • cooling gold liquid until it forms solid gold
   • heating liquid gold until it forms gold vapor
   • cooling gold vapor until it forms liquid gold