Related Experiment Video
Updated: Dec 24, 2025
06:50
Author Spotlight: A Computational Approach to Decipher Amino Acid Preferences in Multispecific Protein-Protein Interactions
Published on: January 26, 2024
2.4K
Predicting Deprotonation Sites Using Alchemical Derivatives
Macarena Muñoz1, Andrés Robles-Navarro2,3, Patricio Fuentealba2,3
1Facultad de Ingenierı́a y Ciencias, Universidad Adolfo Ibañez, Diagonal Las Torres 2640, Santiago 7941169, Chile.
The Journal of Physical Chemistry. A
|April 15, 2020
Summary
Alchemical derivatives accurately rank proton affinity and predict proton dissociation enthalpy for various molecules. Their predictions show strong correlation with experimental and computational data, offering a reliable computational chemistry tool.
Area of Science:
- Computational chemistry
- Physical chemistry
Background:
- Alchemical transformations connect states in chemical space.
- Proton vanishing is key, linking energy to proton dissociation enthalpy.
Purpose of the Study:
- Assess alchemical derivatives for predicting proton dissociation enthalpy.
- Evaluate reliability across diverse mono- and polyprotic molecules.
Main Methods:
- Utilized alchemical derivatives to analyze proton dissociation.
- Compared predictions with energy difference calculations and experimental values.
Main Results:
- Alchemical derivatives excel at ranking proton affinity.
- Predictions show good correlation with established methods.
- Second-order derivatives slightly underestimate enthalpy but offer constant deviation.
Conclusions:
- Alchemical derivatives are reliable for ranking and predicting proton affinity.
- They are accurate for evaluating differences in polyprotic molecules.
- Higher-order derivatives likely explain enthalpy underestimation.
Related Concept Videos
01:10α-Alkylation of Ketones via Enolate Ions
3.7K
Ketones with α protons are deprotonated by strong bases like lithium diisopropylamide (LDA) to form enolate ions. The anion is stabilized by resonance, and its hybrid structure exhibits negative charges on the carbonyl oxygen and the α carbon. This ambident nucleophile can attack an electrophile via two possible sites: the carbonyl oxygen, known as O-attack, or the α carbon, known as C-attack. The nucleophilic attack via the carbanionic site is preferred. This is due to the...
3.7K
01:18Titration of Polyprotic Base with a Strong Acid
4.0K
The titration of a polyprotic base such as sodium carbonate with a strong acid such as hydrochloric acid results in two equivalence points on the titration curve. At the first equivalence point, the carbonate ions in the base are completely converted to bicarbonate ions. The second equivalence point corresponds to the complete conversion of bicarbonate ions to carbonic acid, which dissociates into carbon dioxide and water. The region before the first equivalence point corresponds to the...
4.0K
01:23Titration of Polyprotic Acids with a Strong Base
2.8K
Titration of a polyprotic acid, which contains multiple ionizable protons, involves distinct dissociation steps, each with its own dissociation constant (Ka). Each successive Ka is weaker than the previous one. In the titration of a polyprotic acid like sulfurous acid with a strong base such as sodium hydroxide, the base first neutralizes the initial ionizable proton, forming an intermediate species (e.g., hydrogen sulfite ions). This step's titration curve resembles that of a weak...
2.8K
01:19Composition of Polyprotic Acid Solutions as a Function of pH
782
Polyprotic acids of the type H2M constitute two ionizable protons. As a result, on titration with a base, they exhibit two equivalence points in the titration curve. During titration, the species H2M, HM−, and M2− will be present in the solution at different points. The fractions of H2M, HM−, and M2− present at the various instances of the titration are denoted by α0, α1, and α2, respectively.
A graph with the alpha values is plotted against the volume of...
A graph with the alpha values is plotted against the volume of...
782
01:29Leveling Effect
1.3K
In acid-base chemistry, the leveling effect refers to the limitation imposed by the solvent on the strength of acids and bases in solution. When a base stronger than the solvent's conjugate base is used, it deprotonates the solvent until the base is entirely consumed, making it ineffective against weaker acids. Conversely, an acid stronger than the solvent's conjugate acid protonates the solvent until the acid is depleted, rendering it ineffective against weaker bases. Essentially, the...
1.3K
01:16Titration in Nonaqueous Solvents
1.3K
Most acid-base titrations are performed in an aqueous medium. In aqueous titrations, water competes with weaker acids or bases for proton donation or acceptance, leading to ambiguous endpoints in the titration curve. Water also affects the partial ionization of weak acids or bases. For example, water accepts a proton from acetic acid to form hydronium and acetate ions. The hydronium ion formed is a stronger acid than acetic acid, and the acetate ion is a stronger base than water. As a result,...
1.3K