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Related Concept Videos

Aldehydes and Ketones with Amines: Imine Formation Mechanism01:23

Aldehydes and Ketones with Amines: Imine Formation Mechanism

5.3K
Imine formation involves the addition of carbonyl compounds to a primary amine. It begins with the generation of carbinolamine through a series of steps involving an initial nucleophilic attack and then several proton transfer reactions. The second part includes the elimination of water, as a leaving group, to give the imine.
Imines are formed under mildly acidic conditions. A pH of 4.5 is ideal for the reaction.
If the pH is low or the solution is too acidic, the reaction slows down in the...
5.3K
Aldehydes and Ketones with Amines: Imine and Enamine Formation Overview01:16

Aldehydes and Ketones with Amines: Imine and Enamine Formation Overview

4.4K
Primary amines react with carbonyl compounds—aldehydes and ketones—to generate imines. Imines consist of a C=N double bond and are named Schiff bases after its discoverer—the German chemist Hugo Schiff. On the other hand, secondary amines react with carbonyl compounds to give enamines. In enamines, the presence of a C=C double bond adjacent to the nitrogen atom leads to the delocalization of the lone pair.
4.4K
Aromatic Hydrocarbon Anions: Structural Overview01:18

Aromatic Hydrocarbon Anions: Structural Overview

2.7K
Neutral hydrocarbons like cyclopentadiene with an odd number of carbon atoms and one intervening CH2 group in the ring are not aromatic. Cyclopentadiene with 4 π electrons does not satisfy the 4n + 2 π electron rule. Additionally, the intervening CH2 group is sp3 hybridized and lacks a vacant p orbital, thereby interrupting the overlap of p orbitals in a continuous manner and preventing the delocalization of π electrons throughout the ring.
Due to the absence of continuous...
2.7K
Structure of Amines01:19

Structure of Amines

2.5K
The hybridized nitrogen atom in amines possesses a lone pair of electrons and is bound to three substituents with a bond angle of around 108°, which is less than the tetrahedral angle of 109.5°. However, the C–N–H bond angle is slightly larger at 112°, with a carbon–nitrogen bond length of 147 pm. This carbon–nitrogen bond length of of amines is longer than the carbon–oxygen bond of alcohols (143 pm) but shorter than alkanes’...
2.5K
Aromatic Hydrocarbon Cations: Structural Overview01:18

Aromatic Hydrocarbon Cations: Structural Overview

2.7K
Cycloheptatriene is a neutral monocyclic unsaturated hydrocarbon that consists of an odd number of carbon atoms and an intervening sp3 carbon in the ring. The three double bonds in the ring correspond to 6 π electrons, which is a Huckel number, and therefore satisfies the criteria of 4n + 2 π electrons. However, the intervening sp3 carbon disrupts the continuous overlap of p orbitals. As a result, cycloheptatriene is not aromatic.
Removing one hydrogen from the intervening CH2 group...
2.7K
Structural Isomerism02:34

Structural Isomerism

19.1K
Isomerism in Complexes
Isomers are different chemical species that have the same chemical formula. Structural isomerism of coordination compounds can be divided into two subcategories, the linkage isomers and coordination-sphere isomers.
Linkage isomers occur when the coordination compound contains a ligand that can bind to the transition metal center through two different atoms. For example, the CN− ligand can bind through the carbon atom or through the nitrogen atom. Similarly, SCN− can...
19.1K

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Related Experiment Video

Updated: Jun 5, 2025

Microfluidic-based Synthesis of Covalent Organic Frameworks COFs: A Tool for Continuous Production of COF Fibers and Direct Printing on a Surface
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Microfluidic-based Synthesis of Covalent Organic Frameworks COFs: A Tool for Continuous Production of COF Fibers and Direct Printing on a Surface

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Investigating a Seemingly Simple Imine-Linked Covalent Organic Framework Structure.

Cailing Chen1, Li Cao1, Yaozu Liu2

  • 1Physical Science and Engineering Division (PSE), Advanced Membranes and Porous Materials (AMPM) Center, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia.

Journal of the American Chemical Society
|December 12, 2024
PubMed
Summary
This summary is machine-generated.

Advanced imaging reveals covalent organic frameworks (COFs) possess complex, non-uniform pore structures, challenging existing models. This finding necessitates reevaluation of COF structures and their applications in catalysis and separation.

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Author Spotlight: Characterizing Porous Materials for Aiding the Development of Robust Metal-Organic Frameworks with Adsorption Behavior
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Synthesis and Characterization of Functionalized Metal-organic Frameworks
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Synthesis and Characterization of Functionalized Metal-organic Frameworks
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Synthesis and Characterization of Functionalized Metal-organic Frameworks

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Area of Science:

  • Materials Science
  • Chemistry
  • Nanotechnology

Background:

  • Covalent organic frameworks (COFs) structural determination typically relies on powder X-ray diffraction (PXRD).
  • Limited crystallinity in COFs often leads to low-fidelity structural models.
  • Existing models for a prominent 2D imine-based COF assume uniform hexagonal pores.

Purpose of the Study:

  • To investigate the actual structure of a widely studied 2D imine-based COF using real-space imaging.
  • To challenge the conventional understanding of COF pore uniformity.
  • To establish a more accurate structural model for COFs and their derivatives.

Main Methods:

  • Real-space imaging (e.g., Transmission Electron Microscopy).
  • Reciprocal-space characterizations (e.g., PXRD).
  • Solid-state Nuclear Magnetic Resonance (ssNMR) spectroscopy.
  • Density Functional Theory (DFT) calculations.

Main Results:

  • Real-space imaging revealed two distinct sets of pores with varying shapes and sizes, contradicting uniform hexagonal pore assumptions.
  • A new structural model was established, differing from the conventional model in intra- and interlayer configurations.
  • Previously unrecognized defective structures were identified, impacting COF functionality.

Conclusions:

  • The structure of this landmark COF is more complex and heterogeneous than previously understood.
  • Advanced characterization techniques are crucial for accurate COF structural determination.
  • Identified defects have significant implications for COF applications in separation and catalysis.