Table 6 The assignments of chemical shifts in CNMR of crude, microwave-treated, and ultrasonic-treated21,22,46.
Chemical shifts (ppm) | Assignments |
|---|---|
3–18.5 | Terminal CH3 at the alkyl chains |
18.5–23 | Methyl carbons in α position to aromatic rings |
23–50 | CH2 and CH-type naphthenic and paraffinic carbons |
50–60 | CH and C in paraffinic carbons; C–N in amine groups; C–S; C–S=O |
60–76 | Paraffinic and naphthenic carbon α to OH |
78–100 | Ether/alcohol/ester |
100–129 | Peripheral aromatics |
129–170 | Quaternary aromatic carbon |
170–190 | C=O in Carboxylic acid |
190–200 | Quinolinic carbons |
> 200 | C=O in the aldehyde and ketone |
