For example, the tartaric acid has two stereo isomers namely l-tartaric acid and d-tartaric acid. I want to differentiate both of them by any theoretical calculations using some softwares like Gaussion, VASP and etc., or any other manual calculations. Also please prefer some experimental methods too..
Go through this
Article Chiral Discrimination of D- and L-Amino Acids Using Iodinate...
Dear Sankar,
Density functional theory based calculations (along with many wave function theory based calculations) can be used to differentiate the stereo isomers (structure wise/stability wise). You can use ORCA, TURBOMOLE software for such calculations. The choice of method depends on what type of info you want for the isomers.
Regards,
Biswajit
Dear Biswajit Sadhu,
There is any free version is available for those softwares?
Dear Abdul Amin ,
Thank you for giving a valuable suggestion. I read this full text, but haven't get clear idea. Can you suggest me any other papers or ideas?
Dear Sankar Selvaraj,
The Firflt, MOPAC, and ORCA are the free software.
The following link will help you
https://en.wikipedia.org/wiki/List_of_quantum_chemistry_and_solid-state_physics_software
What do you mean by differentiate? Most quantum chemical programs have front ends that allow you to see the 3-dimensional geometry of the molecule, which would be different for L- and D- versions of a chiral molecule.
However, I'm not aware of any software that automatically assigns an "R" or an "S" to a given chiral molecular structure. This is despite the algorithmic nature of the rule for assignment. (Assigning D and L, apart from amino acids and the like, is less algorithmic and in some cases more a matter of convention. That's why R and S are preferred today.)
I believe there has been some progress on the question of which way a given molecule will rotate polarized light (i.e. assigning + or - to the chiral molecule). But it's still a difficult calculation.
you can draw them in Gaussian view and make calculations, but remember that there are many single bond and this will lead to different conformer for each isomer.
Best.
David, you don't happen to have some reference for the light polarization predictions you mentioned?
Stefan: I may have misspoken. A quick search didn't find anything regarding *visible* light optical activity. I was probably thinking of work in Raman optical activity, where there has been some activity. (For references on that, try "raman optical activity calculations" in Google Scholar).
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