Hydrogenolysis
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2008-04-17T18:39:26Z
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'''Hydrogenolysis''' is a catalytic [[chemical reaction]] whereby a molecule of hydrogen is added over a carbon-heteroatom single bond, effectively causing a "lysis" of the bond. The heteroatom may vary, but usually is oxygen, nitrogen or sulfur. A closely related reaction is [[hydrogenation]], where hydrogen is added over a carbon-carbon double bond (leading to the ultimate reduction to a single bond).
A classic example of hydrogenolysis is debenzylation - the removal of a [[benzyl]] [[protecting group]] usually attached to an oxygen <ref>For example [[Organic Syntheses]], Coll. Vol. 7, p.386 (1990); Vol. 60, p.92 (1981). http://orgsynth.org/orgsyn/pdfs/CV7P0386.pdf</ref> or a nitrogen atom <ref>For example [[Organic Syntheses]], Coll. Vol. 8, p.152 (1993); Vol. 68, p.227 (1990). http://orgsynth.org/orgsyn/pdfs/CV8P0152.pdf</ref>.
With the current knowledge, the only definitive statement that can be made about the ease of hydrogenolysis is that presence of a positive charge (formal or partial) on the heteroatom greatly increases the rate of hydrogenolysis. A proposed mechanism is presented in the [[Hydrogenation#Mechanism_of_reaction|hydrogenation]] article.
A commercial large-scale example of hydrogenolysis is the [[Raney Nickel]] catalyzed "desulfurization" of substituted [[thiophene]] rings, which is a general method for the synthesis of certain hydrocarbons.
The term was coined by [[Homer Burton Adkins]].
==Use in industry==
The catalytic hydrogenation of organic [[sulfur]] compounds to form gaseous [[hydrogen sulfide]] (H<sub>2</sub>S) is very widely used in [[oil refinery|petroleum refineries]], [[petrochemical]] plants and other industries to [[oil desulfurization|desulfurize]] various final products, intermediate products and process feedstocks by converting sulfur compounds to gaseous hydrogen sulfide which is then easily removed by [[distillation]]. The gaseous hydrogen sulfide is subsequently recovered in an [[amine treater]] and finally converted to elemental [[sulfur]] in a [[Claus process]] unit. In those industries, desulfurization process units are often referred to as [[hydrodesulfurization|hydrodesulfurizers]] (HDS) or [[hydrotreater]]s (HDT). In the petroleum refining and petrochemical industries, cobalt-molybdenum or nickel-molybdenum catalysts are commonly used for hydrogenation and hydrogenolysis catalysts.
==References==
{{Reflist}}
[[Category:organic redox reactions]]
[[Category:Hydrogen]]