摘要
合成了一系列六氢吡啶酰胺化合物以研究酰胺键的双键性质.采用1H及13CNMR技术确证了不同取代的酰胺化合物中酰胺键的双键性质.进一步采用变温核磁共振技术对2-(3,5-dinitrophenyl)-1-(piperidin-1-yl)ethanone(化合物1)进行了1H及13CNMR研究.结果表明,在20℃(293 K)时,a,b及c,d上的氢和碳原子具有不同的化学位移,且距酰胺键越近,化学位移的差异越大.随着温度的升高,两种异构体的转换速率增加,酰胺双键的性质越来越不明显,导致化学位移的差异逐渐减小,直至融合为一个峰.经计算,在融合温度下两种异构体的相互转换的速率常数是380s-1,能垒约为67kJ·mol-1.
A series of amides of piperidin were synthesized and used for studies on the partial double-bond feature of the amide bonds. ^1 H and ^13 C NMR spectra of 2-（3, 5-dinitrophenyt）-l- （piperidin-l-yl） ethanone （compound 1） were acquired at various temperatures. The results showed that the C-N bond of the piperidin amides exhibited partially double-bond character at 20 ~C （293 K） , suggesting that the chemical shifts of a and b, c and d in compound 1 were very different due to the two rotameric states. With increasing temperature, the two peaks of non-equivalent -CH2- groups collapsed into one peak due to the fast rotation of the C-N bond. The rate constant for the dynamic process detected for compound 1 was 380 s 1 , and the free energy of activation for compound 1 at coalescence temperature （343 K） was 67 kJ·mo1^-1.
出处
《波谱学杂志》
CAS
CSCD
北大核心
2008年第3期307-314,共8页
Chinese Journal of Magnetic Resonance
关键词
核磁共振
变温核磁
酰胺键
异构体
NMR
variable-temperature experiment
amide bond
isomerization
