1/12/2016 4:17:00 PM1 Dr. Sankarampadi ARAVAMUDHAN NEHU Shillong

Chemistry Materials Polymers Tools for structure determination SPECTROSCOPY Magnetic Resonance Nuclear Magnetic Resonance Spectroscopy of Proton Nuclei A fictitious structure convinces the PMR results Requires further investigation for the chemical reality Computational Chemistry SCHEME FOR THE CONTENTS OF NEXT 9 SLIDES : Slide #2 to #9 Computer Sciences Hardware & Software Programming, Algorithms, Numerical Analysis; Statistics & mathematics Laboratory Instrumentation: Digital Techniques & Automation by computer control Material Sciences Physics CHEMICAL SCIENCES: Chemistry and the aiding branches of Sciences 1)Spectroscopy, NMR/PMR (analytical technique) 2) Computational Chemistry 3) Theoretical Chemistry 1/12/2016 4:17:00 PM2 Dr. Sankarampadi ARAVAMUDHAN NEHU Shillong

Experimental Simulated Structural difference to note is that at CH=CH 2 the double bond is absent in polymer. –CH-CH 2 - (the NMR spectrum consists of broad overlapped lines) 1/12/2016 4:17:00 PM3 Dr. Sankarampadi ARAVAMUDHAN NEHU Shillong

Spectral parameters for the simulation are tabulated as follows: The NMR spin parameters of polymeric styrene parameters can also be possible with a cyclic structure which is only fictitious : referred to as “Spin Book Keeping” structure. For polystyrene Spin parameters of the compound as below result in a spectrum similar to that of polystyrene Would it be possible to inquire for the chemical existence of such fictitious structure with computational Chemistry? 1/12/2016 4:17:00 PM4 Dr. Sankarampadi ARAVAMUDHAN NEHU Shillong

Before making a beginning with the inquiry, the presenting author could get convinced by the possible simulation with the spin parameters that could result from the spin book keeping structure. Simulation software: internet resource 1/12/2016 4:17:00 PM5 Dr. Sankarampadi ARAVAMUDHAN NEHU Shillong

Visualizing a Cyclo addition by the ab initio SCF Methods; a Case Study of Finding Rationale of a Fictitious “Spin bookkeeping” Structure to Simulate NMR spectra. Such a fictitious structure makes possibile the inclusion of certain spin- spin coupling constants for simulation which, otherwise, is not simple enough to infer. Obviously these Spin-Spin interactions occur by mechanisms transmitted through bonds, and it is surprising that a structure which is “fictitious”, can be revealing such through-bond routes by which the exact simulation of the observed NMR spectra. Hence, it was considered worth the while, trying to find out the stability criterion for a dimeric Styrene with the possible QM methods by Geometry Optimization and verify with the calculation of the chemical shifts for such a dimer. A thorough literature survey of the possibility for the occurrence of such dimeric structure of styrene molecule was not undertaken lest those conditions may build up a bias, for an “Only Theoretical Model” by ab initio Calculations. If three successive styrene units of polymer are considered then, if the through bond interactions and circulation-induced fields of the third unit does not influence the proton of the first unit, the entire polymer spectrum would consists of merely dimeric styrene NMR, with possible line broadenings. 1/12/2016 4:17:00 PM6 Dr. Sankarampadi ARAVAMUDHAN NEHU Shillong

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Aromatic plane perpendicular to double arrow head line 1/12/2016 4:17:00 PM10 Dr. Sankarampadi ARAVAMUDHAN NEHU Shillong

? Relevance of Small Molecule Computational Chemistry for the Contexts of Biological Macro molecular Computations Theoretical Chemistry Quantum Chemistry Computational Chemistry Computations with moderate computational facility as much an average Desk top Computer can support Easily accessible and usable provision for beginners Computations with HIGH POWER computational facility / soft wares for parallel processing systems and preferably REQUIRE a full time maintenance staff Often referred to as in silico calculations CHEMISTRY BIOLOGY SCHEME FOR THE CONTENTS OF NEXT 9 SLIDES : Slide #11 onwards 1/12/2016 4:17:00 PM11 Dr. Sankarampadi ARAVAMUDHAN NEHU Shillong

Implications of these remarks to find the possibilities of how small molecule Computational Chemistry can be an aid in the macromolecule computations. This would have a bearing on conventional chemical sciences. CG stands for Coarse Grained 1/12/2016 4:17:00 PM12 Dr. Sankarampadi ARAVAMUDHAN NEHU Shillong

These four configurations have a maximum variation by 6.27 Kcal/mole 1/12/2016 4:17:00 PM13 Dr. Sankarampadi ARAVAMUDHAN NEHU Shillong

Input str. Neutral zwitterion Optimized Str. Neutral non ionic 17 th step 29 th step These stages involve a proton transfer from methyl group to carboxylic oxygen 1/12/2016 4:17:01 PM14 Dr. Sankarampadi ARAVAMUDHAN NEHU Shillong

Proton 8 An example of Experimental 13 C NMR Spectra The CMR image enlarged view 1/12/2016 4:17:01 PM15 Dr. Sankarampadi ARAVAMUDHAN NEHU Shillong

/12/2016 4:17:01 PM16 Dr. Sankarampadi ARAVAMUDHAN NEHU Shillong