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Titration of Polyprotic Base with a Strong Acid01:18

Titration of Polyprotic Base with a Strong Acid

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...
Indicators02:39

Indicators

Certain organic substances change color in dilute solution when the hydronium ion concentration reaches a particular value. For example, phenolphthalein is a colorless substance in any aqueous solution with a hydronium ion concentration greater than 5.0 × 10−9 M (pH < 8.3). In more basic solutions where the hydronium ion concentration is less than 5.0 × 10−9 M (pH > 8.3), it is red or pink. Substances such as phenolphthalein, which can be used to determine the pH of a solution, are called...
Titration of Polyprotic Acids with a Strong Base01:23

Titration of Polyprotic Acids with a Strong Base

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 monoprotic...
Titration of a Polyprotic Acid02:08

Titration of a Polyprotic Acid

A polyprotic acid contains more than one ionizable hydrogen and undergoes a stepwise ionization process. If the acid dissociation constants of the ionizable protons differ sufficiently from each other, then the titration curve for such polyprotic acid generates a distinct equivalence point for each of its ionizable hydrogens. Therefore, titration of a diprotic acid results in the formation of two equivalence points, whereas the titration of a triprotic acid results in the formation of three...
Polyprotic Acids03:38

Polyprotic 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:

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Optical Quantification of Intracellular pH in Drosophila melanogaster Malpighian Tubule Epithelia with a Fluorescent Genetically-encoded pH Indicator
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A colorimetric proton sponge.

Charles D Swor1, Lev N Zakharov, David R Tyler

  • 1Department of Chemistry, University of Oregon, Eugene, Oregon 97403, USA.

The Journal of Organic Chemistry
|September 23, 2010
PubMed
Summary

Researchers synthesized a novel compound, 4-maleicanhydridoproton sponge (MAPS), from Proton Sponge and bromomaleic anhydride. MAPS functions as a color-changing indicator for proton detection, reversible by pH changes.

Area of Science:

  • Organic Chemistry
  • Supramolecular Chemistry
  • Chemical Sensing

Background:

  • 1,8-Bis(dimethylamino)naphthalene, known as Proton Sponge, is a strong organic base.
  • Development of novel compounds with unique acid-base properties is crucial for chemical applications.
  • Colorimetric indicators offer visual detection methods for chemical species and reactions.

Purpose of the Study:

  • To synthesize and characterize a new derivative of Proton Sponge.
  • To investigate the acid-base properties and spectral behavior of the novel compound.
  • To explore its potential as a colorimetric proton sensor.

Main Methods:

  • Reaction of 1,8-Bis(dimethylamino)naphthalene with bromomaleic anhydride at room temperature.
  • Isolation and characterization of the resulting product, 3-(4,5-bis(dimethylamino)napthalen-1-yl)furan-2,5-dione (MAPS).

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  • Spectroscopic analysis (UV-Vis) and acid-base titrations to determine properties.

    • Main Results:

    • Successful synthesis of MAPS, a deep purple solid.
    • MAPS exhibits positive solvatochromism, changing color with solvent polarity.
    • MAPS is a weaker base than Proton Sponge; protonation causes a reversible color loss, enabling colorimetric detection.

    Conclusions:

    • MAPS is a novel, colorimetric derivative of Proton Sponge with tunable basicity.
    • The compound's reversible color change upon protonation/deprotonation makes it a potential visual pH indicator.
    • MAPS offers a new tool for sensing and studying proton transfer processes.