The alkene then complexes with the catalyst surface by using its p orbitals to overlap with the empty metal orbitals of the catalyst. The alkane formed is no longer bound to the metal and diffuses away from the catalyst's surface. The process of hydrogenation is exothermic. For example, although the hydrogenation of both cis butene and trans butene gives the same product — butane, trans butene is more stable than cis butene.
This can be explained based on the heat of hydrogenation of the two isomers. In cis butene, the steric repulsion between the two methyl groups lying on the same side of the double bond makes it less stable, which is reflected in its larger heat of hydrogenation.
To learn more about our GDPR policies click here. If you want more info regarding data storage, please contact gdpr jove. Your access has now expired. Provide feedback to your librarian. If you have any questions, please do not hesitate to reach out to our customer success team.
Login processing Chapter 8: Reactions of Alkenes. Chapter 1: Covalent Bonding and Structure. Chapter 2: Thermodynamics and Chemical Kinetics.
Chapter 3: Alkanes and Cycloalkanes. Chapter 4: Stereoisomerism. Chapter 5: Acids and Bases. Chapter 7: Alkene Structure and Reactivity. Chapter 9: Alkynes. Chapter Alcohols and Phenols. Chapter Ethers, Epoxides, Sulfides. Catalysts are required for the reaction to be usable; non-catalytic hydrogenation takes place only at very high temperatures.
Hydrogenation reduces double and triple bonds in hydrocarbons. Catalytic hydrogenation has diverse industrial uses. Most frequently, industrial hydrogenation relies on heterogeneous catalysts. In petrochemical processes, hydrogenation is used to convert alkenes and aromatics into saturated alkanes paraffins and cycloalkanes naphthenes , which are less toxic and less reactive as well as less corrosive. Hydrocracking of heavy residues into diesel is another application.
Catalytic hydrogenation is hydrogenation in presence of catalysts. Addition of hydrogen to alkenes is an exothermic releasing heat energy reaction, requiring the use of a transition metal catalyst due to the high energy barriers to direct the reaction between alkenes and hydrogen gas. Catalytic hydrogenation of alkynes with transition metal catalysts results in alkanes just like the catalytic hydrogenation of alkenes unless specially deactivated catalysts are used. For the petrochemical industry, many of the compounds found in crude oil are of little use since they contain multiple double bonds; they must be first converted to saturated compounds before use as commodities such as gasoline.
Hydrogenation is also used in coal processing. Solid coal is converted to a liquid through the addition of hydrogen. Liquefying coal makes it available to be used as fuel. Hydrogenation reactions use a catalyst such as palladium, platinum, rhodium, ruthenium or Raney nickel, and are performed at elevated temperature and pressure. Catalytic hydrogenation occurs on the surface of the metal catalyst. Transition metals adsorb hydrogen molecules and pi systems. ACS Nano , 14 10 , ACS Catalysis , 10 7 , The Journal of Physical Chemistry C , 51 , ACS Catalysis , 9 9 , Journal of CO2 Utilization , 47 , Chemosphere , , Zakharov , Nikolay A.
Zhuravlev , Tatiana A. Denisova , Alexander S. Belozerov , Anna Yu. Stroeva , Emma G. Vovkotrub , Andrei S. Farlenkov , Maxim V. Journal of Catalysis , , Brower , Bryan J. Hare , Venkat R. Bhethanabotla , John N. ChemCatChem , 12 24 , Advanced Materials , 32 50 , Applied Surface Science , , International Journal of Hydrogen Energy , 45 51 , Hydrogen adsorption on In 2 O 3 and In 2 O 3 Physical Chemistry Chemical Physics , 22 28 ,
0コメント