Hydrogenolysisis achemical reactionwhereby acarbon–carbonor carbon–heteroatomsingle bond is cleaved or undergoeslysis(breakdown) byhydrogen.[1]The heteroatom may vary, but it usually is oxygen, nitrogen, or sulfur. A related reaction ishydrogenation,where hydrogen is added to the molecule, without cleaving bonds. Usually hydrogenolysis is conducted catalytically using hydrogen gas.
History
editThe term "hydrogenolysis" was coined byCarleton Ellisin reference to hydrogenolysis of carbon–carbon bonds.[1][2]Earlier,Paul Sabatierhad already observed the hydrogenolysis ofbenzyl alcoholtotoluene,[3]and as early as 1906, Padoa and Ponti had observed the hydrogenolysis offurfuryl alcohol.[4]Homer Burton AdkinsandRalph Connorwere the first to call the carbon–oxygen bond cleavage "hydrogenolysis".[1]
In the petrochemical industry
editInpetroleum refineries,catalytic hydrogenolysis of feedstocks is conducted on a large scale to remove sulfur from feedstocks, releasing gaseoushydrogen sulfide(H2S). The hydrogen sulfide is subsequently recovered in anamine treaterand finally converted to elementalsulfurin aClaus processunit. In those industries, desulfurization process units are often referred to ashydrodesulfurizers(HDS) orhydrotreaters(HDT). Catalysts are based onmolybdenum sulfidecontaining smaller amounts of cobalt or nickel. Hydrogenolysis is accompanied by hydrogenation.[5]
Another hydrogenolysis reaction of commercial importance is the hydrogenolysis of esters into alcohols by catalysts such ascopper chromite.
Thehydrodeoxygenationreaction used in theNeste Renewable Dieselprocess, thevegetable oil refiningprocess of largest production capacity, is a hydrogenolysis oftriglyceridesintoalkanes.
In the laboratory
editIn the laboratory, hydrogenolysis is used inorganic synthesis.Debenzylation is most common and involves the cleavage ofbenzylethers:[6]
- R−OCH2C6H5+ H2→ R−OH + CH3C6H5
Thioketalsundergo hydrogenolysis usingRaney nickelin theMozingo reduction.
Laboratory hydrogenolysis is operationally similar tohydrogenation,and may be accomplished at atmospheric pressure by stirring the reaction mixture under a slight positive pressure of hydrogen gas, having flushed the apparatus with more of this gas. The hydrogen may be provided by attaching a balloon to a needle, filling it from a bottle, and inserting the needle into the reaction flask via arubber septum.At high pressure, a hydrogenationautoclave(i.e., a Buchi or Parrhydrogenator) or similar piece of equipment is required.
References
edit- ^abcRalph Connor, Homer Adkins. Hydrogenolysis Of Oxygenated Organic Compounds. J. Am. Chem. Soc.; 1932; 54(12); 4678–4690.doi:10.1021/ja01351a026
- ^Carleton Ellis. Hydrogenation of Organic Substances, 3rd ed., Van Nostrand Company, New York, 1930, p. 564 (as referred by Connor and Adkins).
- ^Sabatier and Murat. Ann. Chim. [9] 4, 258, (1915), according to Connor and Adkins.
- ^Furfuryl alcohol hydrogenation is accompanied by hydrogenolysis into 2-methylfuran, which gives 2-methyltetrahydrofuran, and further hydrogenolysis opens the ring to give 2-pentanol. Original: Padoa and Ponti. Atti. R. accad. Lincei, 15, [5] 610 (1906); Gazz. chim. ital. 37, [2] 105 (1907), according to Kaufmann: W. E. Kaufmann, Roger Adams. The Use Of Platinum Oxide As A Catalyst In The Reduction Of Organic Compounds. Iv. Reduction Of Furfural And Its Derivatives. J. Am. Chem. Soc.; 1923; 45(12); 3029–44.doi:10.1021/ja01665a033
- ^Topsøe, H.; Clausen, B. S.; Massoth, F. E., Hydrotreating Catalysis, Science and Technology, Springer-Verlag: Berlin, 1996.
- ^For example,Organic Syntheses,Coll. Vol. 7, p. 386 (1990); Vol. 60, p. 92 (1981).http://orgsynth.org/orgsyn/pdfs/CV7P0386.pdf.For an example of C-N scission, seeOrganic Syntheses,Coll. Vol. 8, p. 152 (1993); Vol. 68, p. 227 (1990).http://orgsynth.org/orgsyn/pdfs/CV8P0152.pdf