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Basicity of Aliphatic Amines

Basicity of Aliphatic Amines

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...

Amides to Carboxylic Acids: Hydrolysis

Amides to Carboxylic Acids: Hydrolysis

Amides can undergo either acid-catalyzed hydrolysis or base-promoted hydrolysis through a typical nucleophilic acyl substitution. Each hydrolysis requires severe conditions.
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...

Preparation of Amides

Preparation of Amides

Amides are synthesized by treating carboxylic acids with amines in the presence of dehydrating agents like dicyclohexylcarbodiimide (DCC).
The DCC-promoted synthesis of amides begins with the protonation of DCC by carboxylic acid. The protonation makes it a better acceptor. Next, the addition of carboxylate to the protonated carbodiimide gives a reactive acylating agent.
Subsequently, the amine acts as a nucleophile that attacks the acylating agent to form a tetrahedral intermediate. In the...

Ions as Acids and Bases

Ions 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:

Amines to Amides: Acylation of Amines

Amines to Amides: Acylation of Amines

Various carboxylic acid derivatives (such as acid chlorides, esters, and anhydrides) can be used for the acylation of amines to yield amides. The reaction requires two equivalents of amines. The first amine molecule functions as a nucleophile and attacks the carbonyl carbon to produce a tetrahedral intermediate. This is followed by the loss of the leaving group and restoration of the C=O bond.
Next, the second equivalent of amine serves as a Brønsted base and deprotonates the quaternary amide...

Basicity of Heterocyclic Aromatic Amines

Basicity of Heterocyclic Aromatic Amines

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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Related Experiment Video

Updated: May 13, 2026

Quantifying the Binding Interactions Between Cu(II) and Peptide Residues in the Presence and Absence of Chromophores

Quantifying the Binding Interactions Between Cu(II) and Peptide Residues in the Presence and Absence of Chromophores

Published on: April 5, 2022

Cations bind only weakly to amides in aqueous solutions.

Halil I Okur¹, Jaibir Kherb, Paul S Cremer

¹Department of Chemistry, Texas A&M University , College Station, Texas 77843, United States.

Journal of the American Chemical Society

|March 23, 2013

Summary

Metal cations interact weakly with amide groups, mimicking protein backbone interactions. Cation binding strength follows a Hofmeister series, with Ca(2+) showing the strongest interaction but still weak binding constants.

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Structure and Coordination Determination of Peptide-metal Complexes Using 1D and 2D 1H NMR

Structure and Coordination Determination of Peptide-metal Complexes Using 1D and 2D ¹H NMR

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Quantifying the Binding Interactions Between Cu(II) and Peptide Residues in the Presence and Absence of Chromophores

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Ion Mobility-Mass Spectrometry Techniques for Determining the Structure and Mechanisms of Metal Ion Recognition and Redox Activity of Metal Binding Oligopeptides

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Structure and Coordination Determination of Peptide-metal Complexes Using 1D and 2D 1H NMR

Structure and Coordination Determination of Peptide-metal Complexes Using 1D and 2D ¹H NMR

Published on: December 16, 2013

Area of Science:

Biophysical Chemistry
Spectroscopy
Chemical Physics

Background:

Understanding cation-protein backbone interactions is crucial for biological processes.
Butyramide serves as a model compound for studying these interactions in aqueous solutions.

Purpose of the Study:

To investigate salt interactions with butyramide as a mimic of cation interactions with protein backbones.
To determine the binding strength and ordering of metal cations with amide groups.

Main Methods:

Attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy to monitor amide I band shifts in bulk solutions.
Vibrational sum frequency spectroscopy (VSFS) to study cation-amide interactions at the air/water interface.

Main Results:

Well-hydrated metal cations (Ca(2+), Mg(2+), Li(+)) induced shifts in the amide I band, indicating cation-amide binding.
Cation binding led to ordering of adjacent water layers at the interface.
The observed cation ordering followed a Hofmeister series: Ca(2+) > Mg(2+) > Li(+) > Na(+) ≈ K(+).
Apparent equilibrium dissociation constants were weak, with Ca(2+) showing the tightest binding (~8.5 M).

Conclusions:

Cation interactions with amides are significantly weaker than those with weakly hydrated anions.
The study provides direct evidence for a cationic Hofmeister series in cation-amide interactions.