Related Experiment Video
Updated: Jul 8, 2026
11:00
Determination of the Gas-phase Acidities of Oligopeptides
Published on: June 24, 2013
The OH-anion acting as an acid
Lulu Huang1, Lou Massa, Ivan Bernal
1Laboratory for the Structure of Matter, Naval Research Laboratory, Washington, DC 20375-5320, USA.
The Journal of Chemical Physics
|January 22, 2008
Summary
The hydroxide (OH-) anion can act as an acid or base in crystals. Quantum mechanics revealed distinct H3O2- anion structures, with one crystal geometry showing acidic OH- behavior.
Area of Science:
- Physical Chemistry
- Crystallography
- Quantum Mechanics
Background:
- The hydroxide (OH-) anion exhibits amphoteric behavior, acting as both a base and an acid.
- Hydrogen bonding plays a crucial role in the interactions of anions within crystalline structures.
Purpose of the Study:
- To investigate the behavior of the OH- anion in the crystalline state using quantum mechanical calculations.
- To determine the relative stability of different H3O2- anion isomers in three specific crystal environments.
Main Methods:
- Employed four quantum mechanical approximations: Hartree-Fock (HF), B3LYP, SVWN, and Møller-Plesset perturbation theory (MP2).
- Analyzed the geometry and stability of the H3O2- anion in three distinct crystalline samples.
Main Results:
- Identified two qualitatively different structures for the free H3O2- anion, differing in hydrogen bond length.
- Observed a specific crystal state (LICQIX) where the H3O2- anion adopted a geometry indicative of acidic OH- behavior, unlike the free anion.
- Calculated the relative stability of various H3O2- isomers across the studied crystals.
Conclusions:
- The crystalline environment significantly influences the acid-base properties of the OH- anion.
- Quantum mechanical modeling provides insights into the complex behavior of anions in solid-state structures.
- The H3O2- anion exhibits diverse structural possibilities depending on its environment.
More Related Videos
Related Concept Videos
02:54Ions as Acids and Bases
Salts with Acidic Ions
Salts are ionic compounds composed of cations and anions, either of which may be capable of undergoing an acid or base ionization reaction with water. Aqueous salt solutions, therefore, may be acidic, basic, or neutral, depending on the relative acid-base strengths of the salt’s constituent ions. For example, dissolving the ammonium chloride in water results in its dissociation, as described by the equation:
Salts are ionic compounds composed of cations and anions, either of which may be capable of undergoing an acid or base ionization reaction with water. Aqueous salt solutions, therefore, may be acidic, basic, or neutral, depending on the relative acid-base strengths of the salt’s constituent ions. For example, dissolving the ammonium chloride in water results in its dissociation, as described by the equation:
02:16Brønsted-Lowry Acids and Bases
In 1923, the Brønsted–Lowry definition of acids and bases was proposed by Johannes Brønsted and Thomas Lowry. According to this theory, a Brønsted acid is defined as a species that donates a proton in a chemical reaction and gets converted to its conjugate base. A Brønsted base is defined as a species that accepts a proton in a chemical reaction and gets converted into its conjugate acid. These transfers of protons are caused by the displacement of electrons in these reactions, which is...
02:58Bronsted-Lowry Acids and Bases
The acid-base reaction class has been studied for quite some time. In 1680, Robert Boyle reported traits of acid solutions that included their ability to dissolve many substances, to change the colors of certain natural dyes, and to lose these traits after coming in contact with alkali (base) solutions. In the eighteenth century, it was recognized that acids have a sour taste, react with limestone to liberate a gaseous substance (now known to be CO2), and interact with alkalis to form neutral...
01:19Reactions of Acid Anhydrides
The reactions of acid anhydrides are analogous to the reactions of acid chlorides and proceed via a nucleophilic acyl substitution. They only differ in the identity of the leaving group. During an acid chloride reaction, the leaving group is a chloride ion, and the by-product is hydrochloric acid. However, in an acid anhydride reaction, the leaving group is a carboxylate ion, and the by-product is a carboxylic acid.
02:34Molecular Structure and Acidity
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...
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...
03:38Polyprotic Acids
Acids are classified by the number of protons per molecule that they can give up in a reaction. Acids such as HCl, HNO3, and HCN that contain one ionizable hydrogen atom in each molecule are called monoprotic acids. Their reactions with water are: