α—取代呋喃类化合物高分辨^1HNMR特征与取代基效应

THE CHARACTERISTICS OF HIGH RESOLUTION ~1HNMR AND SUBSTITUENT EFFECTS OF α-SUBSTITUTED FURAN COMPOUNDS

呋喃类杂环化合物几乎存在于所有食品中[1]。目前已从不同食品中鉴定出200余种呋喃类化合物,通过剖析和模拟天然食品中香气成分的组成和结构,已研究开发出100余种呋喃类杂环香料[2],许多α呋喃酯类化合物已成为重要的合成香料新品种[3]。本文通过高分辨核磁共振方法研究了...

The results show that the three protons bonded to the α furan ring are chemically and magnetically nonequivalent,and an AMX three spin system is formed.Every proton is split by the other two protons on the α furan ring into an independent quartet,and the coupling constants J AM ;J MX and J AX are 1.8,3.5 and 0.8Hz respectively,activating substituents:δ HX <δ HM ;deactivating substituents:δ HX >δ HM .The two protons bonded to the carbon carbon double bond of α furanacrylic esters are chemically and magnetically nonequivalent,and there is an AB two spin system,every proton on the double bond shows a doublet,the chemical shifts are correspondingly 6.33 and 7.53ppm,the coupling constand is 15.6Hz,this result indicated that the double bond is a trans configuration.If the chemical shift (δ,6.30ppm) of the β proton attached to unsubstituted furan ring is used as a reference standard,deactivating substituents:δ HX >6.30ppm,activating substituents:δ HX <6.30ppm.There is an empirical correlation between the effects of α substituents and the chemical shifts of the β proton on the α furan ring.