The dehydrogenation of alcohols and hydrocarbons by atomic metal anions
Paul Mayer1, Jaleh Halvachizadeh2, Alex Mungham3
1Chemistry Department, University of Ottawa, Ottawa, Canada K1N 6N5. pmmayer@uottawa.ca.
Abstract:
The reactivity of anionic metal-carbonyl systems toward hydrocarbons, alcohols and a variety of other classes of molecules is well established in the literature. In this study we explored the reactions of atomic metal anions M(-), notably K(-), Cs(-), Co(-), Fe(-), Cu(-) and Ag(-), with alcohols, alkanes, alkenes and alkynes. All of the metal anions deprotonated the alcohols and alkynes. Also observed were the subsequent reactions of the resulting organic anions. Fe(-) and Cu(-) consistently displayed mono- and bis-dehydrogenation of primary and secondary alcohols, and alkanes, alkenes and alkynes to form MH(-) and MH(2)(-). Mechanisms for the dehydrogenation reactions are proposed and substantiated with isotopically-labelled reagents and thermochemical arguments.
Related Concept Videos
Alcohols from Carbonyl Compounds: Reduction
Catalytic hydrogenation is similar to the reduction of an alkene or alkyne by adding H2 across the pi bond in the presence of transition metal catalysts like Raney Ni, Pd–C, Pt, or Ru. Aldehydes and ketones can be reduced by this method, often under mild to moderate heat (25–100°C) and...
Reduction of Alkenes: Catalytic Hydrogenation
Metals like palladium, platinum, and nickel are commonly used in their solid forms — fine powder on an inert surface. As these catalysts remain insoluble in the reaction mixture, they are referred to as heterogeneous catalysts.
The hydrogenation process takes place on the...
Reduction of Alkynes to cis-Alkenes: Catalytic Hydrogenation
Like alkenes, alkynes can be reduced to alkanes in the presence of transition metal catalysts such as Pt, Pd, or Ni. The reaction involves two sequential syn additions of hydrogen via a cis-alkene intermediate.
Reduction of Alkenes: Asymmetric Catalytic Hydrogenation
The metal catalyst used can be either heterogeneous or homogeneous. When hydrogenation of an alkene generates a chiral center, a pair of enantiomeric products is expected to form. However, an enantiomeric excess of one of the products can be facilitated using an enantioselective reaction or an...
Hydroboration-Oxidation of Alkenes
Alkynes to Aldehydes and Ketones: Hydroboration-Oxidation
One of the convenient methods for the preparation of aldehydes and ketones is via hydration of alkynes. Hydroboration-oxidation of alkynes is an indirect hydration reaction in which an alkyne is treated with borane followed by oxidation with alkaline peroxide to form an enol that rapidly converts into an aldehyde or a ketone. Terminal alkynes form aldehydes, whereas internal alkynes give ketones as the final product.


