In the acid medium,nitrite can diazotize with p-nitroaniline（PNA）and then couple with diethyl malonate（DM） in basic medium to produce an azo compound,which has the maximum absorption at 496 nm and a molar absorpti...In the acid medium,nitrite can diazotize with p-nitroaniline（PNA）and then couple with diethyl malonate（DM） in basic medium to produce an azo compound,which has the maximum absorption at 496 nm and a molar absorptivity(ε496) of 1.7×104L·mol-1·cm-1.A new spectrophotometric approach for nitrite determination was established on such basis with a detection limit of 1.7×10-7 mol/L.Beer’s law was obeyed in the concentration range of 0.05μg/mL-0.80 μg/mL for sodium nitrite.The proposed method has been applied for the determination of nitrite in vegetables,and the results are satisfactory.展开更多
将L-脯氨酸嫁接在树脂氯球上,催化水杨醛及其衍生物和丙二酸酯直接合成香豆素-3-羧酸酯类物质,反应具有选择性强、产率高、成本低、三废少、后处理简单、催化剂可以多次重复使用等优点,符合绿色催化的特性。实验表明:反应在100℃下,醛...将L-脯氨酸嫁接在树脂氯球上,催化水杨醛及其衍生物和丙二酸酯直接合成香豆素-3-羧酸酯类物质,反应具有选择性强、产率高、成本低、三废少、后处理简单、催化剂可以多次重复使用等优点,符合绿色催化的特性。实验表明:反应在100℃下,醛和酯的摩尔比为1:1.2,催化剂的用量1 g,10 mL DMF中反应5h,反应的选择性≥98%,产率高达92%;催化剂循环使用6次反应的产率仍在85%以上。在此优化的反应条件下,高效合成了一系列其他香豆素-3-羧酸酯类物质,产品的结构和纯度通过了NMR、IR和熔点等手段进行了鉴定。展开更多
文摘In the acid medium,nitrite can diazotize with p-nitroaniline（PNA）and then couple with diethyl malonate（DM） in basic medium to produce an azo compound,which has the maximum absorption at 496 nm and a molar absorptivity(ε496) of 1.7×104L·mol-1·cm-1.A new spectrophotometric approach for nitrite determination was established on such basis with a detection limit of 1.7×10-7 mol/L.Beer’s law was obeyed in the concentration range of 0.05μg/mL-0.80 μg/mL for sodium nitrite.The proposed method has been applied for the determination of nitrite in vegetables,and the results are satisfactory.
文摘将L-脯氨酸嫁接在树脂氯球上,催化水杨醛及其衍生物和丙二酸酯直接合成香豆素-3-羧酸酯类物质,反应具有选择性强、产率高、成本低、三废少、后处理简单、催化剂可以多次重复使用等优点,符合绿色催化的特性。实验表明:反应在100℃下,醛和酯的摩尔比为1:1.2,催化剂的用量1 g,10 mL DMF中反应5h,反应的选择性≥98%,产率高达92%;催化剂循环使用6次反应的产率仍在85%以上。在此优化的反应条件下,高效合成了一系列其他香豆素-3-羧酸酯类物质,产品的结构和纯度通过了NMR、IR和熔点等手段进行了鉴定。
