β-Thioxoketones. Part 6. Electronic absorption spectra of aromatic β-thioxoketones. A study of enol–enethiol tautomerism
作者:Lars Carlsen、Fritz Duus
DOI:10.1039/p29800001768
日期:——
Aromatic β-thioxoketones exist in solution as mixtures of rapidly interconverting Z-enol and Z-enethiol tautomers. The electronic absorption spectra exhibit in general four absorption bands in the u.v.–visible region at ca. 265 (ArCO, π,π*; ArCC π,π*), 330 (ArCS π,π*; OCCCS π,π*; CO n,π*), 415 (OCCCS π,π*), and 520 nm (CS n,π*), respectively. The β-thioxoketones are converted by sodium hydroxide into
芳族β-硫代酮作为快速相互转化的Z-烯醇和Z-烯硫醇互变异构体的混合物存在于溶液中。电子吸收光谱在大约uv的可见光区域一般表现出四个吸收带。265(ArC O,π,π*; ArC Cπ ,π*),330(ArC Sπ ,π*; O CC CSπ,π*; C O n,π*),415(OC CC Sπ, π*)和520 nm(C S n,π*)。β-硫代酮被氢氧化钠转化为相应的阴离子。CNDO / B计算预测,β-硫代木酮酸酯中的负电荷会在OCCCS系统上离域,这表明同时存在镰刀或W形构型。β-硫代酮酸酯的约2个特征吸收带。分别将275和400 nm分配给涉及Ar–C C C–Ar'和S C C C C O发色团的π,π*跃迁。烯醇-烯硫醇互变异构平衡已通过低温光谱法进行了研究。在室温下的平衡常数(K 293已经发现3 - 5的)对应于4:1的烯醇-烯硫醇浓度比。已经发现,反应熵(ΔS r)对