The Competitive O–H versus C–H Bond Activation of Ethanol and Methanol by VO₂⁺ in Gas Phase: A DFT Study

Abstract

The activation of ethanol and methanol by VO₂⁺ in gas phase has been theoretically investigated by using density functional theory (DFT). For the VO₂⁺/ethanol system, the activation energy (Δ<i>E</i>) is found to follow the order of Δ<i>E</i>(C^β–H) < Δ<i>E</i>(C^α–H) ≈ Δ<i>E</i>(O–H). Loss of methyl and glycol occurs respectively via O–H and C^β–H activation, while acetaldehyde elimination proceeds through two comparable O–H and C^α–H activations yielding both VO­(H₂O)⁺ and V­(OH)₂⁺. Loss of water not only gives rise to VO­(CH₃CHO)⁺ via both O–H and C^α–H activation but also forms VO₂(C₂H₄)⁺ via C^β–H activation. The major product of ethylene is formed via both O–H and C^β–H activation for yielding VO­(OH)₂⁺ and VO₂(H₂O)⁺. In the methanol reaction, both initial O–H and C^α–H activation accounts for formaldehyde and water elimination, but the former pathway is preferred