NMR Prediction

Prediction of ¹H-NMR and ¹³C-NMR shift values based on 4000 parameters for 13C NMR and almost 3000 parameters for 1H NMR, chemical shifts are predicted using additivity rules and several strategies of approximation.

Model
Data Set
Output
Prediction Quality
Limitations
References

ChemNMR for ChemDraw
PredictNMR for ISIS™/Draw
Upsol NMRPrediction

Try Online Prediction

Model

Chemical shifts are predicted for all hydrogen or carbon atoms for which additivity rules are available. For a given molecule, the appropriate substructures are automatically assigned following a hierarchical list. These substructures provide the base value of a final predicted shift. Ring systems not available in the data set are approximated by embedded rings and, if necessary, even disassembled into acyclic substructures.

For each substructure found, the remaining parts of the molecule are treated as substituents. Substituents contribute to a final shift by its increments added to the base value. If increments for those substituents are not available so-called embedded substituents, smaller structural units with the same neighbouring atoms, are applied automatically. Or increments of identical or embedded substituents of a corresponding substructure are taken assuming that the effects of the substituents are of the same magnitude.

Models for ethylenes (cis/trans) and cyclohexanes (eq/ax) are also implemented. To use this feature, cyclohexanes must be drawn in the chair conformation.

Data Set

The data set for the ¹H-NMR prediction currently contains 700 base values and about 2000 increments. The ¹³C-NMR prediction tool is based on 4000 parameters.

Output

The output consists of three parts:
1 - the molecular structure with the predicted shifts
2 - a detailed protocol of the prediction process

Question marks given instead of shift values mean that there are no appropriate substructures available in the data set. Shift values in parentheses indicate that the prediction is not complete, that means that the effect of one or more substituents could not be predicted based on data set used.

Prediction Quality

In case of ¹H-NMR, shifts of about 90 % of all CH_x-groups can be predicted with a mean deviation of 0.2 - 0.3 ppm. The use of polar solvents may strongly increase these deviations.
In case of ¹³C-NMR, over 95 % of the shifts can be predicted with a mean deviation of 3.8 ppm.

Limitations

¹H-NMR shifts of hydrogen atoms bonded to hetero atoms are not predicted because they are not only affected by solvents but also by concentration, impurities and steric effects.
In condensed cyclohexane-like rings, gamma corrections cannot be applied for predicting ¹³C-NMR shifts.

References

R. Bürgin Schaller, M. E. Munk and E. Pretsch, J. Chem. Inf. Comput. Sci. 36, 239-243 (1996).
R. Bürgin Schaller, C. Arnold and E. Pretsch, Anal. Chim. Acta 312, 95-105 (1995).
R. Bürgin Schaller, E. Pretsch, Anal. Chim. Acta 290, 295 (1994).
E. Pretsch, A. Fürst, M. Badertscher, R. Bürgin and M. E. Munk, J. Chem. Inf. Comp. Sci. 32, 291-295 (1992).
A. Fürst, E. Pretsch, Anal. Chim. Acta 229, 17 (1990)

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	Prediction of ¹H-NMR and ¹³C-NMR shift values based on 4000 parameters for 13C NMR and almost 3000 parameters for 1H NMR, chemical shifts are predicted using additivity rules and several strategies of approximation.
Model Data Set Output Prediction Quality Limitations References ChemNMR for ChemDraw PredictNMR for ISIS™/Draw Upsol NMRPrediction Try Online Prediction	Model Chemical shifts are predicted for all hydrogen or carbon atoms for which additivity rules are available. For a given molecule, the appropriate substructures are automatically assigned following a hierarchical list. These substructures provide the base value of a final predicted shift. Ring systems not available in the data set are approximated by embedded rings and, if necessary, even disassembled into acyclic substructures. For each substructure found, the remaining parts of the molecule are treated as substituents. Substituents contribute to a final shift by its increments added to the base value. If increments for those substituents are not available so-called embedded substituents, smaller structural units with the same neighbouring atoms, are applied automatically. Or increments of identical or embedded substituents of a corresponding substructure are taken assuming that the effects of the substituents are of the same magnitude. Models for ethylenes (cis/trans) and cyclohexanes (eq/ax) are also implemented. To use this feature, cyclohexanes must be drawn in the chair conformation.
	Data Set
	The data set for the ¹H-NMR prediction currently contains 700 base values and about 2000 increments. The ¹³C-NMR prediction tool is based on 4000 parameters.
	Output
	The output consists of three parts: 1 - the molecular structure with the predicted shifts 2 - a detailed protocol of the prediction process Question marks given instead of shift values mean that there are no appropriate substructures available in the data set. Shift values in parentheses indicate that the prediction is not complete, that means that the effect of one or more substituents could not be predicted based on data set used.
	Prediction Quality
	In case of ¹H-NMR, shifts of about 90 % of all CH_x-groups can be predicted with a mean deviation of 0.2 - 0.3 ppm. The use of polar solvents may strongly increase these deviations. In case of ¹³C-NMR, over 95 % of the shifts can be predicted with a mean deviation of 3.8 ppm.
	Limitations
	¹H-NMR shifts of hydrogen atoms bonded to hetero atoms are not predicted because they are not only affected by solvents but also by concentration, impurities and steric effects. In condensed cyclohexane-like rings, gamma corrections cannot be applied for predicting ¹³C-NMR shifts.
	References
	R. Bürgin Schaller, M. E. Munk and E. Pretsch, J. Chem. Inf. Comput. Sci. 36, 239-243 (1996). R. Bürgin Schaller, C. Arnold and E. Pretsch, Anal. Chim. Acta 312, 95-105 (1995). R. Bürgin Schaller, E. Pretsch, Anal. Chim. Acta 290, 295 (1994). E. Pretsch, A. Fürst, M. Badertscher, R. Bürgin and M. E. Munk, J. Chem. Inf. Comp. Sci. 32, 291-295 (1992). A. Fürst, E. Pretsch, Anal. Chim. Acta 229, 17 (1990)