Formation Pathways toward 2- and 4-Methylbenzaldehyde via Sequential Reactions from Acetaldehyde over Hydroxyapatite Catalyst

Takahiko Moteki, Andrew T. Rowley, Daniel T. Bregante, David W. Flaherty

Research output: Contribution to journalArticlepeer-review

Abstract

Condensation reactions of biomass derived C2 and C4 aldehydes form both ortho- and para-tolualdehydes (2-MB and 4-MB, respectively). The complete reaction network and the detailed mechanisms, however, have not been fully described. Here, analysis of the products formed by sequential condensation reactions of acetaldehyde and 2-butenal suggests that 2- and 4-MB products form via aromatization of 2,4,6-octatrienal and of highly reactive acyclic intermediate(s) formed via self-addition of 2-butenal, respectively. The exact positions at which C−C bonds form between C4 co-reactants to create 4-MB products were investigated by using reactant mixtures containing combinations of 2-butenal, 2-butenol, and 3-methyl-2-butenal as model reactants. The last two reactants can form products that may be assigned to specific reaction pathways (not distinguishable during self-addition of 2-butenal) and also have decreased reactivity at specific carbon atoms. The analysis of the products suggests that 4-MB species form via 2-butenal self-addition by nucleophilic attack of the α-C to the carbonyl-C. Additionally, Diels–Alder reactions (between C6 and C2 intermediates) do not contribute in any significant manner to the formation of 4-MB. These findings complete the description of the reaction network that forms 2- and 4-MB from acetaldehyde on hydroxyapatite.

Original languageEnglish (US)
Pages (from-to)1921-1929
Number of pages9
JournalChemCatChem
Volume9
Issue number11
DOIs
StatePublished - Jun 8 2017

Keywords

  • bioethanol upgrading
  • crotonal
  • hydroxyapatite
  • reaction mechanism
  • tolualdehyde

ASJC Scopus subject areas

  • Catalysis
  • Physical and Theoretical Chemistry
  • Organic Chemistry
  • Inorganic Chemistry

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