The Mechanism of Base-Promoted HF Elimination from 4-Fluoro-4-(4-nitrophenyl)butan-2-one Is E1cB. Evidence from Double Isotopic Fractionation Experiments
作者:Per Ryberg、Olle Matsson
DOI:10.1021/jo010773l
日期:2002.2.1
Leaving-group fluorine and secondary deuterium multiple kinetic isotope effects (KIEs) have been determined for the base-promoted HF elimination from the 4-fluoro-4-(4'-nitrophenyl)-(1,1,1,3,3-(2)H(5))butan-2-one. The fluorine KIE was determined by using the accelerator-produced short-lived radionuclide (18)F in combination with the naturally abundant (19)F. The (19)F substrate was labeled with (14)C
已确定了从4-氟-4-(4'-硝基苯基)-(1,1,1,3,3-)碱促进的HF消除的离去氟和次级氘多重动力学同位素效应(KIE) (2)H(5))丁-2-。通过使用促进剂生产的短寿命放射性核素(18)F与天然富集的(19)F的组合来确定氟KIE。(19)F底物在远处用(14)C标记,以能够测量两种底物的放射性。当使用乙酸盐作为碱时,测定的氟KIE的尺寸为1.0009 +/- 0.0010。甲酸,乙酸盐和咪唑的次级氘KIE分别为1.009 +/- 0.017、1.000 +/- 0.018和1.010 +/- 0.023。与我们最近报道的质子底物的相应KIE相比,这些KIE的大小明显较小。