The photochemistry in methanol of 1-naphthylmethyl phenyl carbonate (3) and 1-naphthylmethyl benzyl carbonate (4) has been studied. Products resulting from both the 1-naphthylmethyl cation and the 1-naphthylmethyl radical are obtained for 3, but only from the cation for 4. Similar results were obtained for the corresponding 1-naphthylmethyl derivatives 5 and 6 of N-phenyl and N-benzyl carbamic acids. The product yields for all four compounds can be explained by a mechanism of initial homolytic cleavage of the 1-naphthylmethyl carbon–oxygen bond from the excited singlet state. The radical pair generated then partitions between the two pathways: electron transfer to form the ion pair or decarboxylation. For PhO-CO-O• and PhNH-CO-O•, decarboxylation is rapid and competitive with electron transfer. For PhCH2O-CO-O• and PhCH2NH-CO-O•, decarboxylation is slower, electron transfer dominates, and only products from the ion pair are obtained.
已研究了1-
萘甲基
苯碳酸甲酯(3)和1-
萘甲基苄基
碳酸甲酯(4)在
甲醇中的光
化学反应。对于3,既从1-
萘甲基离子又从1-
萘甲基自由基得到产物,而对于4,只从离子得到产物。对应的N-苯基和N-苄基
碳酸酰衍
生物5和6的结果类似。所有四种化合物的产物产率可以通过1-
萘甲基碳-氧键的光激发单态态起始自由裂解机制来解释。然后生成的自由基对在两个途径之间分配:电子转移形成离子对或脱羧反应。对于PhO-CO-O•和PhNH-CO-O•,脱羧反应迅速且与电子转移竞争。对于PhCH2O-CO-O•和PhCH2NH-CO-O•,脱羧反应较慢,电子转移占优势,只得到来自离子对的产物。