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Related Concept Videos

Acid Strength and Molecular Structure03:05

Acid Strength and Molecular Structure

31.4K
Binary Acids and Bases
In the absence of any leveling effect, the acid strength of binary compounds of hydrogen with nonmetals (A) increases as the H-A bond strength decreases down a group in the periodic table. For group 17, the order of increasing acidity is HF < HCl < HBr < HI. Likewise, for group 16, the order of increasing acid strength is H2O < H2S < H2Se < H2Te. Across a row in the periodic table, the acid strength of binary hydrogen compounds increases with...
31.4K
Molecular Structure and Acidity02:34

Molecular Structure and Acidity

18.6K
An acid can be deprotonated to form a conjugate base or an anion. If the produced anion is more stable, then the acid is stronger. On the contrary, if the anion is unstable, then the acid is weaker. Hence, to determine the acidity of the compound, the stability of its conjugate base is studied using various factors.
The size effect explains the change in atomic size on acidity. When comparing the acids formed from elements that belong to the same column in the periodic table, their atomic sizes...
18.6K
Acidity of Carboxylic Acids01:21

Acidity of Carboxylic Acids

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Carboxylic acids are the strongest organic acids. However, their acidic strength is much less than mineral acids like HCl. Carboxylic acids ionize in water and readily lose the hydroxyl proton to form a resonance-stabilized carboxylate ion.
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Acidity and Basicity of Carboxylic Acid Derivatives01:25

Acidity and Basicity of Carboxylic Acid Derivatives

3.7K
Carboxylic acids are the strongest among organic acids, as they readily lose the hydroxyl proton to form a resonance-stabilized carboxylate ion. In comparison, the acid derivatives lack acidic hydrogens directly attached to a functional group. In these compounds, the acidic nature arises from their ability to lose α hydrogens, making them weakly acidic.
The relative acidic strength of the derivatives can be explained based on the extent of resonance stabilization of the conjugate base. The...
3.7K
Extraction: Advanced Methods00:56

Extraction: Advanced Methods

568
Metal ions can be separated from one another by complexation with organic ligands–the chelating agent– to form uncharged chelates. Here, the chelating agent must contain hydrophobic groups and behave as a weak acid, losing a proton to bind with the metal. Since most organic ligands used in this process are insoluble or undergo oxidation in the aqueous phase, the chelating agent is initially added to the organic phase and extracted into the aqueous phase. The metal-ligand complex is...
568
Acidity of 1-Alkynes02:42

Acidity of 1-Alkynes

10.2K

The acidic strength of hydrocarbons follows the order: Alkynes > Alkenes > Alkanes. The strength of an acid is commonly expressed in units of pKa — the lower the pKa, the stronger the acid. Among the hydrocarbons, terminal alkynes have lower pKa values and are, therefore, more acidic. For example, the pKa values for ethane, ethene, and acetylene are 51, 44, and 25, respectively, as shown here.
10.2K

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Related Experiment Video

Updated: Oct 11, 2025

Extraction of Lignin with High &#946;-O-4 Content by Mild Ethanol Extraction and Its Effect on the Depolymerization Yield
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Extraction of Lignin with High β-O-4 Content by Mild Ethanol Extraction and Its Effect on the Depolymerization Yield

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Structural characterizations of lignins extracted under same severity using different acids.

Usama Shakeel1, Xinlong Li1, Biao Wang1

  • 1Biochemical Engineering Research Center, Anhui University of Technology, Ma'anshan, Anhui 243032, China.

International Journal of Biological Macromolecules
|December 5, 2021
PubMed
Summary

This study shows that different acids used for lignin extraction, even at the same severity, alter the final lignin structure. This structural variation impacts the suitability of lignin for various applications.

Keywords:
Chemical structural features. 2D-NMR (HSQC)Lignin applicationsLignin valorizationMild acidolysis lignin (MAL)Tailor-made lignin

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Ultrafast Lignin Extraction from Unusual Mediterranean Lignocellulosic Residues
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Ultrafast Lignin Extraction from Unusual Mediterranean Lignocellulosic Residues

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Quantitative 31P NMR Analysis of Lignins and Tannins
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Quantitative 31P NMR Analysis of Lignins and Tannins

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Related Experiment Videos

Last Updated: Oct 11, 2025

Extraction of Lignin with High &#946;-O-4 Content by Mild Ethanol Extraction and Its Effect on the Depolymerization Yield
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Ultrafast Lignin Extraction from Unusual Mediterranean Lignocellulosic Residues
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Quantitative 31P NMR Analysis of Lignins and Tannins
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Quantitative 31P NMR Analysis of Lignins and Tannins

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Area of Science:

  • Biomass Valorization
  • Renewable Feedstocks
  • Green Chemistry

Background:

  • Lignin, a renewable aromatic polymer, offers potential for high-value products.
  • Efficient lignin extraction under mild conditions is crucial for preserving its structure and enabling its use as a petroleum substitute.
  • Lignin Extraction Severity (LES) significantly influences extracted lignin's structure and applications, alongside reagent choice.

Purpose of the Study:

  • To investigate the impact of different strong acid reagents on lignin structure during extraction.
  • To compare lignin structural characteristics obtained using identical Lignin Extraction Severity (LES) but varying acidic media.
  • To determine the suitability of lignin extracted with different reagents for specific applications.

Main Methods:

  • Lignin extraction using 80% aqueous dioxane with H2O, HCl, H2SO4, or HNO3 at a consistent LES (pH 1.30 ± 0.01).
  • Structural characterization employing high-sensitive Nuclear Magnetic Resonance (NMR) spectroscopy (31P and 2D-HSQC).
  • Complementary analysis using Fourier-Transform Infrared (FTIR) spectroscopy and Gel Permeation Chromatography (GPC).

Main Results:

  • Four distinct lignin preparations (L1-L4) were obtained using different acidic conditions.
  • Structural heterogeneity was quantitatively revealed among the extracted lignin samples.
  • NMR, FTIR, and GPC analyses demonstrated significant variations in lignin structure based on the extraction reagent.

Conclusions:

  • The choice of acid reagent critically influences the structural properties of lignin extracted at the same Lignin Extraction Severity (LES).
  • Different acid-mediated extraction processes yield lignins with distinct characteristics, suggesting tailored applications.
  • Understanding these reagent-induced structural differences is key for optimizing lignin valorization strategies.