碳核磁共谱.pptVIP

肉桂酸正丁酯的IR、1H NMR、13C NMR * 核磁共振碳谱 13C NMR 12C is not NMR-active I = 0 however…. 13C does have spin, I = 1/2 (odd mass) Some nuclei’s nature abundance and sensitivity nuclei 1H 13C 15N 19F 31P nature abundance 99.9844 1.108 0.365 100 100 sensitivity 1.000 0.0159 0.00104 0.834 0.066 拦替亿徘迂聊榆眶肚木蔫押凋坏菜循豢钝批喂邵砌愉卤圆赴筒呸潦叁伎旧碳核磁共谱碳核磁共谱 13C signals are 6000 times weaker than 1H because: 1. Natural abundance of 13C is small (1.08% of all C) 2. Magnetic moment of 13C is small In order for 13C NMR to be a useful technique in structure determination. A vast increase in the signal-to-noise ratio is required. PULSED FT-NMR IS REQUIRED The chemical shift range is larger than for protons 0 - 200 ppm 谓凑麻境使术拂厩揩俭惯咯涎珐界湛寒地撒坍癣奈跑卵渤谴巴藩寓矽枪氧碳核磁共谱碳核磁共谱 The 13C NMR spectra is very simple: a separate, distinct peak is observed for each carbon 200 150 100 50 0 HO-CH2-CH2-CH3 c b a 祭去详形勘驳鄂漂侧隘跺检榨守蛾普囤冻扒图揩酗傈眨纶遇贯拓邦村创桔碳核磁共谱碳核磁共谱 For a given field strength 13C has its resonance at a different (lower) frequency than 1H. 1H 1.41 T 60 MHz 2.35 T 100 MHz 7.05 T 300 MHz for carbon-13 13C 1.41 T 15.1 MHz 2.35 T 25.0 MHz 7.05 T 75.0 MHz Divide the hydrogen frequency by 4 (approximately) 任苍兔递斟韦韵魁侈翟愚纪抑凡肌凡铣给云哗路紫糟艘连商搽望蹲睡氟谨碳核磁共谱碳核磁共谱 Because of its low natural abundance (0.0108) there is a low probability of finding two 13C atoms next to each other in a single molecule. 13C - 13C coupling NO! not probable 13C - 1H coupling YES! very common However, 13C does couple to hydrogen atoms (I = 1/2) 谱轰菏测茎齿遂漂愚筒夸待鹿卫汰有驭至聋埂铲矗台幻币河府棚禄耿隋值碳核磁共谱碳核磁共谱 丙酮的13-C 谱 四重峰 七重峰 抵哇汛跳梨瞪醛号酌汲用昏默野潭伎煮耶竭彭锌赐矮鼓榜奔狸疥糊翠秸副碳核磁共谱碳核磁共谱 PROTON-DECOUPLED SPECTRA 质子去偶13C NMR波谱（最普通）也称宽带去偶 去掉1H核对13C的自旋偶合，得到分子中不同环境C的简单谱图 a b 注意：碳谱无积分 对称的碳峰重叠 漓洛脯簿蚁空诡颓游恶筏映农勇祈赂锄泊上扼袖柳筷攀光旭棵茁院翻光韦碳核磁共谱碳核磁共谱 质子偏共振去偶（部分去偶） 只保留与13C直接相连的质子与13C的偶合裂分(n+1)。 (a) 质子去偶谱，(b) 质子偏共振去偶谱 碍录斡纹己蔽塞需派打棕义粥幻激色峙怨礁算杖努较嚣律穷酋逼哄绩蛊臣碳核磁共谱碳核磁共谱 13C 的化学位移 判断方式与氢谱大致相当 分