Abstract: Using tetramethyl silicane (TMS) as an external reference, solvent effect on chemical shifts of five extracting solvents, N-methyl-2-pyrrolidone (NMP), sulfolane, N,N-dimethylformamide (DMF), N,N-dimethyl-acetamide (DMA), and γ-butyrolactone (γ-BL), has been investigated in C_6—C_9 aromatics relative to carbon tetrachloride at 60.0 MHz and 36 ℃.
In the aromatic solvents, it has been observed that signals of the extracting molecules shifted significantly to high field and the resonance lines of NMP and γ-BL were splited or overlapped. The upfield shifts of the molecules decrease as the number of methyl group on aromatic ring increases. The extent of upfield shift in styrene is the largest among C_6—C_9 aromatics for NMP, DMF, DMA, and sulfolane. Considering the thermodynamic results obtained previously, it can be deduced that weak chemical interactions between molecules of the extracting solvents and the aromatic hydrocarbons may be existent.

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