Related Experiment Video
Updated: May 27, 2026

Quantitative 31P NMR Analysis of Lignins and Tannins
Published on: August 2, 2021
Structural characterization of lignins isolated from Caragana sinica using FT-IR and NMR spectroscopy
Ling-Ping Xiao1, Zheng-Jun Shi, Feng Xu
1College of Material Science and Technology, Beijing Forestry University, Beijing 100083, China. lingpingxiao@gmail.com
Abstract:
In order to efficiently explore and use woody biomass, six lignin fractions were isolated from dewaxed Caragana sinica via successive extraction with organic solvents and alkaline solutions. The lignin structures were characterized by Fourier transform infrared spectroscopy (FT-IR) and 1D and 2D Nuclear Magnetic Resonance (NMR). FT-IR spectra revealed that the "core" of the lignin structure did not significantly change during the treatment under the conditions given. The results of 1H and 13C NMR demonstrated that the lignin fraction L2, isolated with 70% ethanol containing 1% NaOH, was mainly composed of beta-O-4 ether bonds together with G and S units and trace p-hydroxyphenyl unit. Based on the 2D HSQC NMR spectrum, the ethanol organosolv lignin fraction L1, extracted with 70% ethanol, presents a predominance of beta-O-4' aryl ether linkages (61% of total side chains), and a low abundance of condensed carbon-carbon linked structures (such as beta-beta', beta-1', and beta-5') and a lower S/G ratio. Furthermore, a small percentage (ca. 9%) of the linkage side chain was found to be acylated at the gamma-carbon.
Related Concept Videos
Spectroscopy of Carboxylic Acid Derivatives
In the...
IR Frequency Region: Fingerprint Region
The...
IR and UV–Vis Spectroscopy of Carboxylic Acids
However, the stretching absorptions for the C=O bond vary depending on the structure of carboxylic acids. The C=O bond of the free carboxylic acids shows a higher stretching frequency, 1760 cm−1, while H-bonded carboxylic acids (dimers) exhibit stretching absorptions at a lower frequency, 1710 cm−1. The C=O bond of the...
NMR Spectroscopy of Aromatic Compounds
IR Spectrum
Transmittance is defined as the ratio of the radiant power passing through a sample to that from the radiation's source. Multiplying the transmittance by 100 gives the percent transmittance (%T), which varies between 100% (no absorption) and 0% (complete...
NMR and Mass Spectroscopy of Carboxylic Acids
While α protons of carboxylic acids absorb at 2–2.5 ppm, β protons absorb further upfield.
Carboxylic acids are easily identified by dissolving them in deuterium oxide, which results in a rapid exchange of the acidic protons with deuterium. This leads to the disappearance of the acidic...

