title: Thermal transformation of bioactive caffeic acid on fumed silica seen by UV-Vis spectroscopy, thermogravimetric analysis, temperature programmed desorption mass spectrometry and quantum chemical methods.
abstract: Thermochemical studies of hydroxycinnamic acid derivatives and their surface complexes are important for the pharmaceutical industry, medicine and for the development of technologies of heterogeneous biomass pyrolysis. In this study, structural and thermal transformations of caffeic acid complexes on silica surfaces were studied by UV-Vis spectroscopy, thermogravimetric analysis, temperature programmed desorption mass spectrometry (TPD MS) and quantum chemical methods. Two types of caffeic acid surface complexes are found to form through phenolic or carboxyl groups. The kinetic parameters of the chemical reactions of caffeic acid on silica surface are calculated. The mechanisms of thermal transformations of the caffeic chemisorbed surface complexes are proposed. Thermal decomposition of caffeic acid complex chemisorbed through grafted ester group proceeds via three parallel reactions, producing ketene, vinyl and acetylene derivatives of 1,2-dihydroxybenzene. Immobilization of phenolic acids on the silica surface improves greatly their thermal stability.
authors.affiliation: Chuiko Institute of Surface Chemistry of National Academy of Sciences of Ukraine, 17 General Naumov Street, Kyiv 03164, Ukraine. Electronic address: tanyakulyk@i.ua.
authors.forename: Tetiana V
authors.initials: TV
authors.lastname: Kulik
authors.affiliation: Chuiko Institute of Surface Chemistry of National Academy of Sciences of Ukraine, 17 General Naumov Street, Kyiv 03164, Ukraine.
authors.forename: Natalia O
authors.initials: NO
authors.lastname: Lipkovska
authors.affiliation: Chuiko Institute of Surface Chemistry of National Academy of Sciences of Ukraine, 17 General Naumov Street, Kyiv 03164, Ukraine.
authors.forename: Valentyna M
authors.initials: VM
authors.lastname: Barvinchenko
authors.affiliation: Chuiko Institute of Surface Chemistry of National Academy of Sciences of Ukraine, 17 General Naumov Street, Kyiv 03164, Ukraine.
authors.forename: Borys B
authors.initials: BB
authors.lastname: Palyanytsya
authors.affiliation: Chuiko Institute of Surface Chemistry of National Academy of Sciences of Ukraine, 17 General Naumov Street, Kyiv 03164, Ukraine.
authors.forename: Olga A
authors.initials: OA
authors.lastname: Kazakova
authors.affiliation: Chuiko Institute of Surface Chemistry of National Academy of Sciences of Ukraine, 17 General Naumov Street, Kyiv 03164, Ukraine.
authors.forename: Olesia O
authors.initials: OO
authors.lastname: Dudik
authors.affiliation: Department of Physical Chemistry and Material Science, Budapest University of Technology and Economics, H-1521 Budapest, Hungary; Institute of Materials Science and Environmental Chemistry, Research Center for Natural Sciences, Hungarian Academy of Sciences, Hungary.
authors.forename: Alfréd
authors.initials: A
authors.lastname: Menyhárd
authors.affiliation: Department of Physical Chemistry and Material Science, Budapest University of Technology and Economics, H-1521 Budapest, Hungary.
authors.forename: Krisztina
authors.initials: K
authors.lastname: László
mesh_terms: D002109:Caffeic Acids / Q000737:chemistry*; D013058:Mass Spectrometry; D015394:Molecular Structure; D010316:Particle Size; D011789:Quantum Theory; D012822:Silicon Dioxide / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet; D013499:Surface Properties; D013696:Temperature; D013818:Thermogravimetry
chemical_list: D002109:Caffeic Acids; D012822:Silicon Dioxide; C040048:caffeic acid
keywords: Hydroxycinnamic acid derivatives; Kinetic parameters; Silica; Surface complexes; Temperature-programmed desorption mass spectrometry; Thermal transformation