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An Unexplored O-2-Involved Pathway for the Decarboxylation of Saturated Carboxylic Acids by TiO2 Photocatalysis: An Isotopic Probe Study
Wen, Bo; Li, Yue; Chen, Chuncheng; Ma, Wanhong; Zhao, Jincai
2010
Source PublicationCHEMISTRY-A EUROPEAN JOURNAL
ISSN0947-6539
Volume16Issue:39Pages:11859-11866
AbstractThe aerobic decarboxylation of saturated carboxylic acids (from C-2 to C-5) in water by TiO2 photocatalysis was systematically investigated in this work. It was found that the split of C-1-C-2 bond of the acids to release CO2 proceeds sequentially (that is, a C-5 acid sequentially forms C-4 products, then C-3 and so forth). As a model reaction, the decarboxylation of propionic acid to produce acetic acid was tracked by using isotopic-labeled (H2O)-O-18. As much as approximate to 42% of oxygen atoms of the produced acetic acids were from dioxygen (O-16(2)). Through diffuse reflectance FTIR measurements (DRIFT'S), we confirmed that an intermediate pyruvic acid was generated prior to the cut-off of the initial carboxyl group; this intermediate was evidenced by the appearance of an absorption peak at 1772 cm(-1) (attributed to C=O stretch of alpha-keto group of pyruvic acid) and the shift of this peak to 1726 cm(-1) when (H2O)-O-16 was replaced by (H2O)-O-18. Consequently, pyruvic acid was chosen as another model molecule to observe how its decarboxylation occurs in (H2O)-O-16 under an atmosphere of O-18(2). With the alpha-keto oxygen of pyruvic acid preserved in the carboxyl group of acetic acid, approximate to 24% new oxygen atoms of the produced acetic acid were from molecular oxygen at near 100% conversion of pyruvic acid. The other approximate to 76% oxygen atoms were provided by H2O through hole/OH radical oxidation. In the presence of conduction band electrons, O-2 can independently accomplish such C-1-C-2 bond cleavage of pyruvic acid to generate acetic acid with approximate to 100% selectivity, as confirmed by an electrochemical experiment carried out in the dark. More importantly, the ratio of O-2 participation in decarboxylation increased along with the increase of pyruvic acid conversion, indicating the differences between non-substituted acids and alpha-keto acids. This also suggests that the O-2-dependent decarboxylation competes with hole/OH-radical-promoted decarboxylation and depends on TiO2 surface defects at which Ti-4c sites are available for the simultaneous coordination of substrates and O-2.
KeywordCarboxylic Acids Decarboxylation Isotopic Labeling Photocatalysis Titanium Dioxide
DOI10.1002/chem.201001704
Indexed BySCI
Language英语
WOS IDWOS:000283834500016
PublisherWILEY-BLACKWELL
Citation statistics
Cited Times:27[WOS]   [WOS Record]     [Related Records in WOS]
Document Type期刊论文
Identifierhttp://ir.iccas.ac.cn/handle/121111/70716
Collection中国科学院化学研究所
Corresponding AuthorMa, Wanhong
AffiliationChinese Acad Sci, Inst Chem, Key Lab Photochem, Beijing Natl Lab Mol Sci, Beijing 100190, Peoples R China
Recommended Citation
GB/T 7714
Wen, Bo,Li, Yue,Chen, Chuncheng,et al. An Unexplored O-2-Involved Pathway for the Decarboxylation of Saturated Carboxylic Acids by TiO2 Photocatalysis: An Isotopic Probe Study[J]. CHEMISTRY-A EUROPEAN JOURNAL,2010,16(39):11859-11866.
APA Wen, Bo,Li, Yue,Chen, Chuncheng,Ma, Wanhong,&Zhao, Jincai.(2010).An Unexplored O-2-Involved Pathway for the Decarboxylation of Saturated Carboxylic Acids by TiO2 Photocatalysis: An Isotopic Probe Study.CHEMISTRY-A EUROPEAN JOURNAL,16(39),11859-11866.
MLA Wen, Bo,et al."An Unexplored O-2-Involved Pathway for the Decarboxylation of Saturated Carboxylic Acids by TiO2 Photocatalysis: An Isotopic Probe Study".CHEMISTRY-A EUROPEAN JOURNAL 16.39(2010):11859-11866.
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