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如何用TLC监控反应过程(翻译)

2009-02-04 11:45阅读:
1.选择展开剂体系使得反应物的Rf在0.3-0.4之间
polar compounds: 100% EtOAc or 5% MeOH/dichloromethane
normal compounds: 10-50% EtOAc/Hexane
nonpolar compounds: 5% EtOAc/hexane, 5% ether/hexane, 100% hexane
2.在展开瓶内放入0.5cm左右的混合溶剂
3.准备TLC板(1.5-2cm宽,5cm高,固定相:硅胶、铝板等,通常加入荧光粉,在254nm紫外灯下显亮绿色),在底物画一水平线,用铅笔点三个点(点间距离需超过0.5cm),并保证这些点不会没入溶剂中。
4.取一定原料稀释至反应体系浓度,在最左面和中间用毛细管点点,点不能太大。(如果原料多于一种,需要点超过3个点)
5.用毛细管取反应液在中间和右面点点。中间的点为“cospot”
6.爬板至接近顶部
7.在紫外灯下观察并将点圈出
8.在空气中或热台上使板上溶剂干掉。
9.将板子浸适合的TLC着色剂中,在热台上加热。多实验几次以便找到合适的着色剂。
There are various techniques to visualize the compounds.
1. Sulfuric acid/heat: destructive, leaves charred blots behind

2. Ceric stain: destructive, leaves a dark blue blot behind for polar compounds
3. Iodine: semi-destructive, iodi
ne absorbs onto the spots, not permanent

4. UV light: non-destructive, long wavelength (background green, spots dark), short wavelength (plate dark, compounds glow), Do not look into the UV lamp!!!

Circle the spots on the TLC plate to have a permanent record how far the compound traveled on the plate. Also draw a sketch of the developed plate in your lab notebook.

Tip:不要将热板浸入KMnO4中,但是可以将热板浸入茴香醛(对甲氧基苯甲醛)中效果较好。
如何用TLC监控反应过程(翻译)
(图片来源:http://www.chem.ucla.edu/~bacher/General/30BL/tips/TLC1.html
The Rf (=retardation factor) depends on the following parameters:
  • solvent system
  • absorbent (grain size, water content, thickness)
  • amount of material spotted
  • temperature

原文:http://chem.chem.rochester.edu/~nvd/tlchowto.html



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