Reaction Mechanisms in the Direct Carboxylation of Alcohols for the Synthesis of Acyclic Carbonates

Aresta, Michele and Dibenedetto, Angela and Angelini, Antonella and Pápai, Imre (2015) Reaction Mechanisms in the Direct Carboxylation of Alcohols for the Synthesis of Acyclic Carbonates. TOPICS IN CATALYSIS, 58 (1). pp. 2-14. ISSN 1022-5528

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Dialkylcarbonates, (RO)(2)CO, can be prepared from alcohols and CO2. Such reaction is clean (water is the co-product) but thermodynamically disfavored. In principle, the reaction mechanism of formation of carbonates requires the acid-base activation of alcohols. Existing data support that the first step is the formation of the alkoxo group RO- that reacts with CO2 to give the hemicarbonate moiety ROC(O)O-. The latter converts into the relevant carbonate (RO)(2)CO following different pathways depending on the catalyst used. DFT calculations have been used in a few cases to support the reaction mechanism. Transition states relevant to various mechanistic scenarios have been identified. The results indicated that the relative energies of these transition states depend on the nature of the alkyl group and the molecularity of the reactive step. Organic catalysts, homogeneous-, heterogenized- and heterogeneous-metal systems are discussed in this paper and the known relevant mechanisms compared. Water represents a serious limitation to equilibrium shift to the right and can affect the catalysts. Techniques used to remove water are also discussed.

Item Type: Article
Uncontrolled Keywords: CO2; ALKOXIDES; DIMETHYLCARBONATE; METHANOL; DIOXIDE; MILD CONDITIONS; ZIRCONIA CATALYSTS; selective synthesis; ORGANIC CARBONATES; Dimethyl carbonate; Water removal; reaction mechanism; Alcohols carboxylation; Organic acyclic carbonates
Subjects: Q Science / természettudomány > QD Chemistry / kémia
Depositing User: MTMT SWORD
Date Deposited: 14 Jun 2016 14:02
Last Modified: 14 Jun 2016 14:02

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