Deoxygenation is achemical reaction involving the removal ofoxygen atoms from a molecule. The term also refers to the removal of molecular oxygen (O2) from gases and solvents, a step inair-free technique andgas purifiers. As applied toorganic compounds, deoxygenation is a component offuels production as well a type of reaction employed inorganic synthesis, e.g. ofpharmaceuticals.
Compounds with an oxygen atom removed can be described as "desoxy-" or "deoxy-" relative to the original compound, for instancedeoxyribose ordesoxymescaline.
The main examples involving the replacement of an oxo group by two hydrogen atoms (A=O → AH2) arehydrogenolysis. Typical examples use metal catalysts and H2 as the reagent. Conditions are typically more forcing thanhydrogenation.[citation needed]
Stoichiometric reactions that effect deoxygenation include theWolff–Kishner reduction for aryl ketones. The replacement of ahydroxyl group by hydrogen (A-OH → A-H) is the point of theBarton–McCombie deoxygenation and theMarkó–Lam deoxygenation.[citation needed]
Deoxygenation is an important goal of the conversion of biomass to useful fuels and chemicals. Partial deoxygenation is effected bydehydration anddecarboxylation.[1]
Oxygen groups can also be removed by the reductive coupling of ketones, as illustrated by theMcMurry reaction.
Epoxides can be deoxygenated using the oxophilic reagent produced by combiningtungsten hexachloride andn-butyllithium generates thealkene. This reaction can proceed with loss or retention of configuration.[2][3]
Nitroaromatics are deoxygenated by strongly reducing silyl reagents such asN,N'-bis(trimethylsilyl)-4,4'-bipyridinylidene.[4]
Phosphorus occurs in nature as oxides, so to produce elemental form of the element, deoxygenation is required. The main method involvescarbothermic reduction (i.e., carbon is the deoxygenation agent).
Oxophilic main group compounds are useful reagents for certain deoxygenations conducted on laboratory scale. The highly oxophilic reagenthexachlorodisilane (Si2Cl6) stereospecifically deoxygenatesphosphine oxides.[5][6]
A chemical reagent for the deoxygenation of many sulfur and nitrogen oxo compounds is the combinationtrifluoroacetic anhydride/sodium iodide.[7] For example, in the deoxygenation of thesulfoxidediphenylsulfoxide to thesulfidediphenylsulfide:
Thereaction mechanism is based on the activation of the sulfoxide by a trifluoroacetyl group and oxidation of iodine.Iodine is formed quantitatively in this reaction and therefore the reagent is used for the analytical detection of many oxo compounds.
