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Related Concept Videos

Basicity of Aromatic Amines01:18

Basicity of Aromatic Amines

8.3K
The basicity of aromatic amines is much weaker than that of aliphatic amines due to the involvement of the lone pair of electrons over the N atom in resonance with the aryl rings. Generally, the electron-donating ability of any substituents on the aryl ring of aromatic amines increases the basicity of the amine by increasing electron density, and hence the availability of lone pair on the nitrogen. On the other hand, electron-withdrawing functional groups on the aryl ring of amines decrease the...
8.3K
Basicity of Aliphatic Amines01:21

Basicity of Aliphatic Amines

7.1K
Amines can behave as Brønsted–Lowry bases by accepting a proton from the acid to form corresponding conjugate acids. Due to a lone pair of nonbonding electrons, aliphatic amines can also act as Lewis bases by forming a covalent bond with an electrophile.
To measure the basicity of amines, two conventions are generally used. The first defines Kb as the basicity constant for the deprotonation reaction of water by the amine, as presented in Figure 1. Conventionally, lower Kb indicates higher...
7.1K
Basicity of Heterocyclic Aromatic Amines01:25

Basicity of Heterocyclic Aromatic Amines

7.1K
Heterocyclic amines, where the N atom is a part of an alicyclic system, are similar in basicity to alkylamines. Interestingly, the heterocyclic amine having a nitrogen atom as part of an aromatic ring has much less basicity than its corresponding alicyclic counterpart. For this reason, as presented in Figure 1, piperidine (pKb = 2.8) is significantly more basic than pyridine (pKb = 8.8).
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Acidity of 1-Alkynes02:42

Acidity of 1-Alkynes

11.4K

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.
11.4K
Acidity and Basicity of Carboxylic Acid Derivatives01:25

Acidity and Basicity of Carboxylic Acid Derivatives

4.5K
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...
4.5K
Acidity and Basicity of Alcohols and Phenols02:36

Acidity and Basicity of Alcohols and Phenols

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Like water, alcohols are weak acids and bases. This is attributed to the polarization of the O–H bond making the hydrogen partially positive. Moreover, the electron pairs on the oxygen atom of alcohol make it both basic and nucleophilic. Protonation of an alcohol converts hydroxide, a poor leaving group, into water—a good one. The two acid–base equilibria corresponding to ethanol are depicted below.
22.7K

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Related Experiment Video

Updated: Mar 18, 2026

Preparation and Reactivity of a Triphosphenium Bromide Salt: A Convenient and Stable Source of PhosphorusI
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Preparation and Reactivity of a Triphosphenium Bromide Salt: A Convenient and Stable Source of PhosphorusI

Published on: November 22, 2016

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Experimental Basicities of Superbasic Phosphonium Ylides and Phosphazenes.

Jaan Saame1, Toomas Rodima1, Sofja Tshepelevitsh1

  • 1Institute of Chemistry, University of Tartu , 14a Ravila Str, 50411 Tartu, Estonia.

The Journal of Organic Chemistry
|July 9, 2016
PubMed
Summary

This study reports the strongest phosphonium ylide superbases, creating a reliable basicity scale in THF up to pKa 35. This scale aids future research and predicts high basicities in acetonitrile.

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Metal-free Synthesis of Ynones from Acyl Chlorides and Potassium Alkynyltrifluoroborate Salts
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Area of Science:

  • Organic Chemistry
  • Physical Chemistry

Background:

  • Superbases are crucial in organic synthesis.
  • Measuring and comparing basicities of strong bases is challenging.

Purpose of the Study:

  • To establish a self-consistent experimental basicity scale for superbases in Tetrahydrofuran (THF).
  • To synthesize and characterize new phosphonium ylide superbases.
  • To correlate basicity data between THF and acetonitrile.

Main Methods:

  • Synthesis of novel phosphonium ylide compounds.
  • Experimental determination of basicities using potentiometric titration.
  • Compilation of a pKa scale spanning over 30 units.
  • Correlation analysis between THF and acetonitrile basicity data.

Main Results:

  • A comprehensive experimental basicity scale for superbases in THF was established, reaching an estimated pKa of 35.
  • The basicity of 47 compounds, including newly synthesized ones, was determined.
  • The solution basicity of the phosphazene superbase t-Bu-N═P4(dma)9 was rigorously linked to the THF scale.
  • A strong correlation between basicities in THF and acetonitrile was found, enabling prediction of pKa > 40 in acetonitrile.

Conclusions:

  • The developed basicity scale in THF is a valuable tool for future studies.
  • The correlation allows for the estimation of extremely high basicities in acetonitrile.
  • Structure-basicity relationships were analyzed.