I Lab Services 

4.3 CNMR Predictor 

CNMR Predictor quickly and precisely calculates 

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C NMR spectra for almost any drawn organic 

structure.  The calculated chemical shifts are always provided with the confidence limits, so that 

you always know how far the calculated values can be trusted. 

In most cases, the CNMR Predictor module calculates chemical shifts with an accuracy of 3 ppm 

or better.  For this purpose, the module uses a large internal data base with over 2,017,000 

experimental chemical shifts and 81,400 coupling constants for 165,000 structures.  To quantitate 

intramolecular interactions in new organic structures and to predict their chemical shifts, CNMR 

Predictor module uses a unique algorithm based on the intramolecular interaction parameters for 

over 3,000 structural fragments, which have been carefully derived from the experimental data 

using the specially developed CNMR data processing approaches.  It calculates the spin spin 

interaction of carbon nuclei with the magnetic nuclei of other elements, proceeding from the 

natural ratio of magnetic isotopes.  Calculated chemical shifts and coupling constants are 

provided with 95% confidence intervals so that you know the reliability of the calculated values. 

ACD/CNMR recognizes spectral differences between the following types of isomeric structures: 

Cis trans isomers of alkenes; 

Cis trans and endo exo isomers of cyclic structures; and 

Syn anti isomers of amides, oximes, hydrazones, and nitrosoamines. 

The results of CNMR spectrum prediction can be viewed from a special dialog box that appears 

automatically as soon as the results are received from the server (if the corresponding check box 

is selected in the ACD/I Lab Options dialog box) or that can be opened from the Task Manager 

by clicking Result. 

The results are represented in the form of a spectrum that can be viewed with the external viewer 

(CNMR Viewer) that is included into the ChemSketch installation package by default. 

4.4 PNMR Predictor 

ACD/PNMR Predictor accurately calculates 

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P NMR chemical shifts and coupling constants for 

many typical chemical structures containing P.  It uses parameters gleaned from its internal 

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P 

database, which contains over 28,200 chemical shifts and 19,400 coupling constants for over 

22,600 structures. 

The resultant table of chemical shifts includes the following information: 

The type of nucleus giving rise to the nuclear magnetic resonance (here, it is 

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P); 

The number of the atom in the structure which gives rise to the predicted shift; 

The value of the predicted shift; and 

The uncertainty of the predicted shift, based on 95% confidence limits for the structure 

fragment. 

The table of coupling constants displays: 

The type of nucleus giving rise to the nuclear magnetic resonance coupling (here, it is 

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P); 

The numbers of the two atoms in the structure which give rise to the coupling; 

The value of the predicted coupling; and 

ACD/I Lab via ChemSketch  

User's Guide 

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