Barriers to rotation in methyl formate by dynamic NMR spectroscopy and barriers to 1,3 oxygen-to-oxygen migration in methyl formate and trifluoromethyl formate by ab initio calculations.
Barriers to rotation in methyl formate by dynamic NMR spectroscopy and barriers to 1,3 oxygen-to-oxygen migration in methyl formate and trifluoromethyl formate by ab initio calculations.
复制标题
通过动态核磁共振波谱分析甲酸甲酯中的旋转势垒，通过从头计算计算甲酸甲酯和甲酸三氟甲酯中的 1,3 氧到氧迁移的势垒。
DOI：
10.1021/jo0103726
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发表时间：
2001
期刊：
影响因子：
--
通讯作者：
E. Noe
中科院分区：
文献类型：
--
作者：
D. Cain;D. Pawar;M. Stewart;H. Billings;E. Noe
在-70.8℃下，动态核磁共振谱对富含13C的甲酸甲酯(1)的E-Z转化率和Z-E转化率的自由能垒分别为9.85和11.91+/-0.15千卡/摩尔，对碳甲酸甲酯[13C(2)]的转化率为99%。这些势垒高于报道的-53℃的文献值。甲酸甲酯中甲基1，3氧向氧迁移的自由能势垒是通过从头计算在几个水平上确定的。在MP2/6-311+G(df，pd)水平上得到的58.7kcal/mol的值与该过程的文献障碍(MINDO/3)和相关化合物的障碍进行了比较。在MP2/6-31+G水平上计算了CF3基团在三氟甲酸甲酯(3)中氧向氧迁移的自由能垒为63.0kcal/mol。
Free-energy barriers of 9.85 and 11.91 +/- 0.15 kcal/mol at -70.8 degrees C were found by dynamic NMR spectroscopy for the E-to-Z and Z-to-E conversions, respectively, of methyl formate (1) enriched in 13C to 99% for the carbonyl carbon [methyl formate 13C (2)]. These barriers are higher than the literature values reported for -53 degrees C. The free-energy barrier to 1,3 oxygen-to-oxygen migration of the methyl group in methyl formate was determined by ab initio calculations at several levels. The value of 58.7 kcal/mol obtained at the MP2/6-311+G (df,pd) level was compared to a literature barrier for this process (MINDO/3) and to barriers for related compounds. A free-energy barrier of 63.0 kcal/mol for the oxygen - to - oxygen migration of the CF3 group in trifluoromethyl formate (3) was calculated at the MP2/6-31+G level.