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7/6/2012 11:50:10 AMAravamudhan: Chiral Recognition by NMR1 Chiral Recognition by NMR Spectroscopy- A Theoretical approach. Illustrating modeling strategies.

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Presentation on theme: "7/6/2012 11:50:10 AMAravamudhan: Chiral Recognition by NMR1 Chiral Recognition by NMR Spectroscopy- A Theoretical approach. Illustrating modeling strategies."— Presentation transcript:

1 7/6/ :50:10 AMAravamudhan: Chiral Recognition by NMR1 Chiral Recognition by NMR Spectroscopy- A Theoretical approach. Illustrating modeling strategies with organic molecules with overtones for Modeling of Bio-molecules An Abstract This material may be availed as Internet Resource: Display the web subdirectory: Some of the linked files in this.ppt file require the Software ARGUSLAB be installed in your system. Download the MS Windows installer setup.exe file by clicking on the link below: The setup file is in the folder arguslab as mentioned in the link above. Download the contents of the folder, create a folder by name arguslab in your sytem, and save all the contents of the link folder in your resident disk-folder If this presentation file is saved to the resident disc, and if the slideshow is running while the internet connection is available in the P.C., then all the hyperlinks would display the appropriate files from the internet. S.Aravamudhan

2 JPG Image Full publication by Bagatur Yants et al 7/6/ :50:10 AM2Aravamudhan: Chiral Recognition by NMR Cs D3d In the D3d all oxygen are disposed towards the cavity of the molecule In the Cs there are interatomic distances for favorable hydrogen bonding

3 Crown Ether-18crown6-D3d-webmo computational result The JPG image The JPG Image 7/6/ :50:10 AM3Aravamudhan: Chiral Recognition by NMR The several perspective views of the D3d structure which seems to be occurring more in the polar media

4 18crown6-Cs form-computational results The JPG Image 7/6/ :50:10 AM4Aravamudhan: Chiral Recognition by NMR The several perspective views of the Cs structure which seems to be occurring more in the nonpolar media

5 The JPG ImageCrown Ether-18crown6-D3d-webmo computational result 7/6/ :50:10 AM5Aravamudhan: Chiral Recognition by NMR The two-line spectrum of the 18-crown-6 ether, due to the fluctuations and conformational dynamics in solution gives a single averaged line spectrum as much as the cyclohexane (Chair). The experimental PMR spectrum of 18crown6ether displays a single line spectrum at 3.691ppm, this value is higher than the average value of the two-line theoretical spectrum {~( )/2=2.25ppm}. Such differences can be reconciled by using a better QM method of calcualtion (-and a scaling seems inevitable in any case). Link:- data base experimental spectrumas the cyclohexane (Chair). data base experimental spectrum

6 The JPG Image 18crown6-Cs form-computational results 7/6/ :50:10 AM6Aravamudhan: Chiral Recognition by NMR Job Str-PMR-CMR-C12H24O6- Crownether-form2-65.JPG Cyclohexane-boat for comparison

7 The JPG ImageThe Full publication by Koylu et al 7/6/ :50:10 AM7Aravamudhan: Chiral Recognition by NMR The variety of Derivatives of 18- crown-6 ether which are used in the experimental methods; For complexing with chiral molecules and proceed to obtain NMR of the complex. The 18crown6ether in the PMR spectrum has simply a single line; it is not necessary that the derivatives should also have similar single line. Characteristic variations in certain specific nmr line is often possible to recognize the chirality (of the host) dependent variations (as in next slide #7) Typically referred to as NMR titration: A specific line in the spectrum of the complex displays a variation with the relative guest/host concentration ratio.

8 The JPG Image The Full publication by Koylu et al 7/6/ :50:10 AM8Aravamudhan: Chiral Recognition by NMR The specific NMR line position variation for the S and R conformers. The actual complex (the Host and gust) can be seen in the next slide #8 What makes these kind of studies tedious and prone with ambiguities is: the experimental search for appropriate Guest and Host molecules which would enable some line in the spectrum to be tagged on to distinguish chiral - dependence Hence the query as to whether theoretical calculations would reduce the uncertainties; the quest for appropriate theoretical method is duly the initiative required; Is it then simply a matter of calculating chemical shifts accurately, or the better G.O. possibilities?

9 The JPG Image The Full publication by Koylu et al 7/6/ :50:10 AM9Aravamudhan: Chiral Recognition by NMR This docked complex does indicate that a Theoretical Calculation would entail the complications of docking studies in the macromolecular regime (the hyperlinks should display the AGL files and the corresponding exported images). Thus such a supra molecule studies could derive benefit by modeling with small molecules for favorable features to know the specifics which can then be integrated into a set of conditions for a tangible study of the large molecule. This indication for the necessity for a modeling was pursued to gain some insight and the full comprehension of the actualities, regarding the Chiral Recognition by NMR using theoretical methods, would require several compilations of the type presented now, and in the remaining parts.Theoretical Calculationentail the complications of docking studies Hyperlink-1 Hyperlink-2

10 The JPG Image Computation on Cyclohexane-chair 7/6/ :50:10 AM10Aravamudhan: Chiral Recognition by NMR CYCLOHEXANE-analogous symmetry and conformational disposition Return to Slide #4

11 The JPG Image Computation on Cyclohexane-boat 7/6/ :50:10 AM11Aravamudhan: Chiral Recognition by NMR CYCLOHEXANE-analogous symmetry and conformational disposition Return to Slide #5


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