Related Experiment Video
Updated: Aug 12, 2026

Orientational Transition in a Liquid Crystal Triggered by the Thermodynamic Growth of Interfacial Wetting Sheets
Published on: May 15, 2017
Conformational transition of hyaluronic acid: carboxylic group participation and thermal effect
Abstract:
The chiroptical, viscosity and titration studies of hyaluronic acid in mixed organic/water solvent show a reversible conformational transition of the molecule depending upon pH, solvent composition, temperature, and molecular weight. Neither methylhyaluronate nor chondroitin undergoes conformational transition of this type. These results indicate that hydrogen bonding between the protonated carboxylic group and carbonyl oxygen of the acetamido group is directly involved in the conformational change. Results with chondroitin provide further support for the 4-fold helical structure that we have proposed for hyaluronic acid in mixed organic/water solvent. The thermal stability of the conformation has been studied under various pH values and solvent compositions.
Related Concept Videos
Chair Conformation of Cyclohexane
The hydrogen atoms linked to carbons are arranged in two different axial and equatorial orientations to achieve this staggered...
Regioselectivity and Stereochemistry of Acid-Catalyzed Hydration
¹H NMR of Conformationally Flexible Molecules: Temporal Resolution
Acid Halides to Carboxylic Acids: Hydrolysis
As shown below, the mechanism involves a nucleophilic attack by water at the carbonyl carbon to form a tetrahedral intermediate. This is followed by the reformation of the carbon–oxygen π bond along with the departure of a halide ion. A final proton transfer step yields carboxylic acid...
Amides to Carboxylic Acids: Hydrolysis
Acid-catalyzed hydrolysis:
Hydrolysis of amides under acidic conditions yields carboxylic acids. Since the reaction occurs slowly, hydrolysis requires the conditions of heat.
The mechanism begins with the protonation of the carbonyl oxygen by the acid catalyst. The protonation makes the amide carbonyl carbon more...
¹H NMR of Conformationally Flexible Molecules: Variable-Temperature NMR

