Abstract:

Inductive effect is one of the most important effects in organic chemistry. We propose a new inductive effect parameter for neutral groups (I_G), which describes the “inner-shielding” and “outer-shielding” effects in NMR. It was shown that the ¹³C NMR chemical shifts (CS) of alcohols can be predicted from I_G, polarization effect index (PEI) and α, β, γ structural parameters as follow:

CS=-2.3+[20.696 7(ΣΔI)+18.386 5(ΣΔPEI)-0.011 1(ΣΔI/ΣΔPEI)

+1.239 7(ΣΔPEI/ΣΔI)-5.800 9N^α_C+4.260 4N^β_C-1.758 3

-3.346 0N^γ_C+32.376 3]. 
Experimental results showed that the above model had good stability and predictive ability. The correlation coefficient R of the equation was found to be 0.994 7, and the cross-validation correlation coefficient R_CV by the LOO method was 0.992 7.

Key words: ¹³C NMR, chemical shift, inductive effect, polarization effect, alcohol