Let's use a chemical shift prediction tool in JASON! Confirmation of analysis results by chemical shift prediction (1)

The results of structural analysis by NMR should be judged based on consistency with various measurement data. In recent years, there has been remarkable development in software-based chemical shift prediction. By comparison of actual chemical shift values with chemical shift prediction, it's possible to improve the accuracy of analysis. Here, we report an example to use a chemical shift prediction tool in JASON*. (JASON: JEOL Analytical Software Network)

Confirmation of an estimated structure by HMBC

Here is an example of analysis of a compound whose molecular formula is C₆H₁₀O₂. In this compound, two estimated structures I and II were derived by measurements of ¹³C, DEPT, HMQC and COSY (Fig. 1). The difference is the position of the oxygen bonding to the carbonyl carbon  F. Therefore we measured HMBC, which could detect long range ¹H-¹³C correlations, usually 2 or 3 bonds apart. The result showed carbonyl carbon F had three correlations with H_C, H_D, and H_E. In estimated structure I, all these protons exist within 3 bonds, while in structure II, correlation between F and H_E is apart 4 bonds. Thus, we can consider structure I is correct.

Confirmation of an estimated structure by a chemical shift prediction tool in JASON

The accuracy of the analysis can be further improved by using HMBC in combination with a chemical shift prediction tool in JASON. The chemical shift prediction tool was applied to both estimated structures I and II (Fig. 3). Table. 1 shows the actual and predicted values of the chemical shifts. The predicted values of estimated structure I had good agreement with the actual values. Thus, we can be more confident that structure I is the correct structure.

Solutions by field

Chemistry

Related products

Nuclear Magnetic Resonance Spectrometer (NMR)

Next Generation NMR Data Analysis Software JASON