以NMR手段为主进行结构分析一则

某固体化合物极易溶于水但未能制得其单晶.为测定其结构可充分发挥NMR的特长.利用NMR的多种技术,包括常规¹H谱、¹³C谱,一维、二维谱,确定脂肪链X-CH₂-CH₂-CH₂-Y与芳香基团Y的存在;利用¹³C-¹H长程耦合相关谱(用反相探头)可确定脂肪链与芳香基团间的联接关系,于是立即可确定该物的有机主体骨架应为X-CH₂-CH₂-CH₂-Y.从IR谱得知该物除存在C-N基团外,还存在-SO₃-基团等.从元素成分分析和M8谱,包括FAB-MS谱等分析结果,最终推断该固体化合物为丙磺酸吡啶内鎓盐,它的分子结构应为:

AN EXAMPLE OF STRUCTURE ANALYSIS BY NMR TECHNIQUE AS IMPORTANT MEANS

An unknown white solid compound is very soluble in water.Its single crystal is not obtained now.The NMR technique plays an important role in determining its structure.From the routine ¹H NMR spectrum (Fig.1),¹³C NMR spectrum,decoupling without NOE ¹³C NMR spectrum,off-resonace ¹³C NMR spectrum,(Fig.3),¹H-¹H COSY spectrum (Fig.2),and ¹³C-¹H correlated 2D spectrum (Fig.4),it proves that there are an alkylchain X-CH₂-CH₂-CH₂-Y and an aromatic group Y in this compound.¹³C-¹H correlated spectrum via long range couplings (in inverse probe)(Fig.5) may determine how to connect between the chain and the group.So its main skeletal must be X-CH₂-CH₂-CH₂-Y.IR spectrum (Fig.6),shows us theexistance of the-SO₃-group.From the results of element analysis and MS spectrum,including FAB-MS spectrum (Fig.7 and 8),It was finally judged that the molecular structure of this compound should be the internal salt of pyridinium-N-propane-sulfonic acid.Its structural formula is .