hi,

start witth 

u v , i r, ms, proton nmr, carbon nmr, cosy and next all. 

all the best

Hello Rao,

structural elucidation of unknown compounds can be very challenging, and there is no straight-away single procedure to follow. Usually it is a good idea to start with determination of the molecular formula: C's and H's can be obtaind from 13C- and 1H-NMR, possible elemental compositions can be calculated from HRMS. Don't forget to look at isotopic patterns in the MS as they indicate certain elements (Cl, Br are easily recognizable, S, Si are a bit more difficult). Then, try to identify functional groups by looking at UV, IR and NMR spectra. Some structural elements/functional groups may show themselves as characteristic fragments or mass differences in the MS. The next step would be to identify structural elements of the carbon backbone; for this you use mainly the NMR spectra, as they give you information about C's and H's which are neighbored - especially the various 2D NMR spectra provide a wealth of information here. Make sure that you cross-check every structural motif you believe to have found by looking at the other spectra you have. Finally, you try to put all structural elements together to a reasonable structure which should match all experimental data.

This would be a very simplified strategy. In many cases, it is not straight forward because spectral information are not as unambiguous as one would like them to be. That means, there is usually a lot cross-checking and pitfall, of trial and error before you have a reasonable structure proposal. And keep in mind: Your result will be a structure proposal, not a proof! A structure proposal is regarded to be proven only when the proposed structure has been synthesized and shown to give exactly the same spectra as those you started with.

In that sense, good luck!

Thomas Dülcks

Thank you so much Thomas Dülcks  Sir for your useful information.. i shall start with same strategy..  

Dear Ajay,

I would recommend instead of carrying out sophisticated characterization understand that natural molecules belong to particular class of compounds e.g tannins, flavonoids, sterols, glycosides, coumarins, aquinones etc. you first carry out the chemical tests to confirm the class of compounds. This can then be followed by carrying out TLC (refer Plant Drug Analysis by Wagner) once this is done you are aware of basic nucleus then you can revisit the spectroscopic data, the interpretation will be much quicker

You can start first literature by which you can make some idea to nature and type of compounds present in it, after that try to find out molecular weight by Mass, after that 13 C NMR which will give the information of no. of carbon present and its corresponding mass, remaining mass can be checked by filling H atoms, Nitrogen rule tell you presence of Halogen atoms. After molecular mass and formula then the role of 2D NMR explain you relation between C & H. FT-IR tells you nature of functional groups only

First of all you have to be sure that you have a clean individual substance in your hands. To do this, thin layer chromatography can be performed in a suitable solvent system. I agree with Galvina Ferreira that a qualitative reaction showing to which class of natural compounds your substance belongs can be very useful. Then use the spectroscopic techniques that are available to you.