I'm trying to prepare hydrazide from ester of meclofenamic acid. By tlc is showing 3 spots one of them is of product, I don't know what two others are. What should I do
Check the solubility of your crude product.
If this is insoluble in chloroform or ethanol, use these solvents for washing.
If washing doesn't work, try recrystallization.
Check purity of your methyl ester of meclofenamic acid. The acid form will not react directly with hydrazine. Did you conduct microwave assisted reaction - in 2011 a succesfull procedure has been published for your substance you want to make.
Microwave-Assisted One-Step Synthesis of Fenamic Acid Hydrazides from the Corresponding Acids (nih.gov)
What was an NMR of your reaction mixture looking like ? your final product seems to be 2-(2,6-Dichloro-3-methylphenylamino)benzohydrazide (3c) White fibers; Mp: 155-157 °C (reported [29] 158-160 °C). 1 H-NMR δ: 2.38 (s, 3H, CH3), 4.57 (s, D2O exch., 2H, NH2), 6.21 (d, 1H, J = 8 Hz, ArH), 6.77 (t, 1H, J = 7 Hz, ArH), 7.22 (t, 1H, J = 7 Hz, ArH), 7.29 (d, 1H, J = 8 Hz, ArH), 7.48 (d, 1H, J = 8 Hz, ArH), 7.62 (d, 1H, J = 8 Hz, ArH), 9.74 (s, D2O exch., 1H, NH), 9.89 (s, D2O exch., 1H, NH). 13C NMR δ: 20.13, 113.29, 115.82, 117.62, 127.87, 128.06, 128.34, 129.27, 131.60, 132.36, 135.21, 136.39, 144.65, 168.16. MS m/z (%): 310 (M+ ).
If you are sure where the spot of your target product is, the crude reaction product is solid and the visual intensity of the other spots under UV is very weak, you can try successive recrystallizations from suitable solvent. That could give you a product of satisfactory purity for spectral analysis or engaging in next-step reactions (although this method will decrease the actual yield of your product).
If the spots of your product and other side products/SMs are of equal intensity, it's better to separate them using flash column chromatography or preparative HPLC (if available in your lab) then submitting the isolated compounds to spectral analysis to identify your target reaction product (this method is better for either cases, although it's more time and effort-consuming).
You can try changing the solvent to wash. Alternatively, purification can be carried out using other methods such as recrystallization, distillation, chromatographic columns, etc.
- Badges
- Science topic