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Title: Towards understanding of laccase-catalysed oxidative oligomerisation of dimeric lignin model compounds
Authors: Ramalingam, B
Sana, B
Seayad, J
Ghadessy, F.J
Sullivan, M.B 
Keywords: Catalysis
Chemical bonds
Density functional theory
Free energy
High performance liquid chromatography
Liquid chromatography
Mass spectrometry
Reaction intermediates
Spectroscopic analysis
Thermodynamic stability
Free-energy difference
Lignin model compound
Mass spectroscopy
Product formation
Reaction progress
Relative free energy
Spectroscopic method
Thermodynamically stable
Mass Spectroscopy
Issue Date: 2017
Citation: Ramalingam, B, Sana, B, Seayad, J, Ghadessy, F.J, Sullivan, M.B (2017). Towards understanding of laccase-catalysed oxidative oligomerisation of dimeric lignin model compounds. RSC Advances 7 (20) : 11951-11958. ScholarBank@NUS Repository.
Rights: Attribution 4.0 International
Abstract: Laccase-catalysed oligomerisation of dimeric ?-O-4 linked lignin model compounds was studied in detail to understand the oligomerisation process by monitoring the reaction progress using high performance liquid chromatography (HPLC) and mass spectroscopy (MS). The initial oxidation intermediates of oligomerisation were isolated for the first time and characterised by spectroscopic methods sucessfully. The experimental observations indicated that C5-C5? biphenyl linkages, one of the most thermodynamically stable linkages present in the native lignin, are formed exclusively during the early stage of the oligomerisation process. The experimental observations were supported by density functional theory (DFT) calculations of relative free energies of possible products. The C5-C5? biphenyl tetramer is the thermodynamically more favoured product compared to the C5-O-C4? product by a free energy difference of 10.0 kcal mol?1 in water. Among the various linking possibilities for further formation of hexamers, the thermodynamically more stable product with a similar C-C linkage is proposed as a plausible structure based on the mass of the hexamer isolated and DFT calculations. The current study demonstrates that laccase catalyzes the oligomerisation more preferentially than oxidative bond cleavage in ?-O-4 linkages and that product formation is likely controlled by the thermodynamic stability of the resultant oligomers. © The Royal Society of Chemistry.
Source Title: RSC Advances
ISSN: 20462069
DOI: 10.1039/c6ra26975c
Rights: Attribution 4.0 International
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