title: DFT investigation on the decarboxylation mechanism of ortho hydroxy benzoic acids with acid catalysis.
abstract: A density functional theory (DFT) study was performed to explore the mechanisms of the acid-catalyzed decarboxylation reaction of salicylic acids using the B3LYP method with 6-31++G(d,p) basis set in both gas phase and aqueous environment. The α-protonated cation of carboxylate acid was formed during the decarboxylation process in acidic conditions, and the presence of hydrogen ions promotes decarboxylation greatly by significantly decreasing the overall reaction energy barriers to 20.98 kcal mol(-1) in gas phase and 20.93 kcal mol(-1) in water, respectively. The hydrogen in the α-carbon came directly from the acid rather than from the carboxyl group in neutral state. Compared with the reaction in gas phase, water in aqueous state causes the reaction to occur more easily. Substituents of methyl group, chlorine and fluorine at the ortho-position to the carboxyl of salicylic acid could further lower the decarboxylation energy barriers and facilitate the reaction.
authors.affiliation: Key Laboratory of Industrial Fermentation Microbiology (Tianjin University of Science & Technology), Ministry of Education, College of Bioengineering, Tianjin University of Science and Technology, Tianjin, 300457, People's Republic of China.|Department of Life Science and Engineering, Jining University, Qufu, 273155, Shandong Province, People's Republic of China.
authors.forename: Yanying
authors.initials: Y
authors.lastname: Hu
authors.affiliation: Key Laboratory of Industrial Fermentation Microbiology (Tianjin University of Science & Technology), Ministry of Education, College of Bioengineering, Tianjin University of Science and Technology, Tianjin, 300457, People's Republic of China.
authors.forename: Lu
authors.initials: L
authors.lastname: Gao
authors.affiliation: College of Food Science and Technology, Wuhan Polytechnic University, Wuhan, 430023, Hubei Province, People's Republic of China.
authors.forename: Zhoutong
authors.initials: Z
authors.lastname: Dai
authors.affiliation: Key Laboratory of Industrial Fermentation Microbiology (Tianjin University of Science & Technology), Ministry of Education, College of Bioengineering, Tianjin University of Science and Technology, Tianjin, 300457, People's Republic of China.
authors.forename: Guojuan
authors.initials: G
authors.lastname: Sun
authors.affiliation: Key Laboratory of Industrial Fermentation Microbiology (Tianjin University of Science & Technology), Ministry of Education, College of Bioengineering, Tianjin University of Science and Technology, Tianjin, 300457, People's Republic of China.
authors.forename: Tongcun
authors.initials: T
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Industrial Fermentation Microbiology (Tianjin University of Science & Technology), Ministry of Education, College of Bioengineering, Tianjin University of Science and Technology, Tianjin, 300457, People's Republic of China.
authors.forename: Shiru
authors.initials: S
authors.lastname: Jia
authors.affiliation: Key Laboratory of Industrial Fermentation Microbiology (Tianjin University of Science & Technology), Ministry of Education, College of Bioengineering, Tianjin University of Science and Technology, Tianjin, 300457, People's Republic of China. yujiedai@sina.com.
authors.forename: Yujie
authors.initials: Y
authors.lastname: Dai
authors.affiliation: Key Laboratory of Industrial Fermentation Microbiology (Tianjin University of Science & Technology), Ministry of Education, College of Bioengineering, Tianjin University of Science and Technology, Tianjin, 300457, People's Republic of China. zxl1966@hotmail.com.
authors.forename: Xiuli
authors.initials: X
authors.lastname: Zhang
keywords: Acid-catalyzed; Decarboxylation; Density functional theory; Salicylic acid