¹³C NMR Chemical Shift Substituent Effects: Empirical Substituent Effects in β-Alcoxyvinyl Halomethylketones

Abstract

This work presents the evaluation by empirically derived equations for the substituent effect (α, β, γ, δ) on the ¹³C NMR chemical shifts for C-1, C-2, C-3 and C-4 in β-alcoxyvinylhalomethylketones 1a–h to 3a–h [R³C(O)-C(R²)=C(R¹-OR, where R¹ = H, alkyl or phenyl, R² = H, alkyl or hetero-alkyl, and R³ = di- or trihalomethyl], taking as reference the compound la. From the calculated values for the α, β, γ, δ effects for each substituent it was possible to estimate the chemical shift of each carbon of the compounds 1–3. The ¹³C chemical shifts of the C-1, C-2, C-3, C-4 of these compounds, can be estimated with good to rasoable precision: 93% of the calculated chemical shifts are found to be within ±2.0ppm, and 100% are found to be within ±3.0ppm.

Key Words:

• ¹³C NMR of β-Alcoxyvinylketones
• Substituent Effects
• ¹³C NMR of Trisubstituted alkenes

Notes

Delta-13C-BII, Marcos A. P. Martins, 1992, Departamento de Química, Universidade Federal de Santa Maria, Santa Maria, RS, Brasil.