Why does sabatier sendersens reaction for nickel using temperature but pt not using?
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Answer:
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Explanation:
This reaction can be traced back to Debus's transformation of hydrocyanic acid into methylamine over platinum in 1863, De Wilde's hydrogenation of acetylene into ethylene and ethane in 1874, (1) and Mond's extensive work from 1890 to 1895. (2) However, it was in 1899 that Sabatier and Senderens established nickel‐based hydrogenation (3) and converted the unsaturated organic molecules (e.g., ketones, aldehydes, alkenes and aromatics) into corresponding saturated compounds (i.e., alcohols, hydrocarbons) by passing the vapor of organic molecules and hydrogen over hot, finely divided nickel.
This nickel‐based vapor phase hydrogenation became one of the most practically useful reactions and won Sabatier the Nobel Prize in 1912. (1) It is generally known as the Sabatier‐Senderens reduction. (4)
This reaction is different from reductions using nascent hydrogen as the reducing agent, such as amalgam of sodium in alcohol (alkaline condition) and or zinc or tin with hydrochloric acid (acidic medium). In this reaction, the purity of nickel and reaction temperature are found to be critical for successful hydrogenation. (1) For example, trace amounts of sulfur, bromine, or iodine will deactivate the nickel catalyst; in addition, it has been found that each hydrogenation process takes place only within a well‐defined temperature range, (1) as evidenced by the hydrogenation of benzene to cyclohexane at temperatures ranging from 70° to 190°C, with an optimal temperature between 170° and 190°C, and the further reduction of benzene to methane accompanied by the deposited carbon on nickel at temperatures > 300°C. (5) Under the correct hydrogenation conditions, Sabatier et al. successfully converted oleic acid into stearic acid, acetone to isopropanol, carbon monoxide into methane or a gaseous mixture rich in methane, phenol and p‐cresol into cyclohexanol and p‐methylcyclohexanol, benzene to cyclohexane, and naphthalene to tetralin, etc. (1) All these reductions afford the expected products, except for the hydrogenation of naphthalene; other reducing methods may lead to the unexpected products, as demonstrated by the reduction of benzene with hydroiodic acid at 250°C to afford methyl cyclopentane, (1) and the hydrogenation of only one phenyl group of triphenylcarbinol over the Adam's platinum oxide catalyst. (6) At the same time, Sabatier et al. also found that the reduced cobalt, iron, copper, and powdered platinum have catalytic activities similar to nickel. Copper in particular is known to be superior to nickel during the hydrogenation of nitrobenzene to aniline, due to its insensitivity to accidental impurities. (1) It is interesting that Sabatier was able to reduce naphthalene into only tetralin, (7, 8) other researchers have successfully converted naphthalene into decalin over nickel.