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Related Concept Videos

Five-Membered Heterocyclic Aromatic Compounds: Overview01:13

Five-Membered Heterocyclic Aromatic Compounds: Overview

Heterocyclic aromatic compounds are cyclic compounds that are aromatic and have one or more heteroatoms—atoms other than carbon, in the ring. Depending upon the number of atoms present in the ring, they can be either five or six-membered. Examples of five-membered heterocyclic aromatic compounds include pyrrole, furan, thiophene, and imidazole. Pyrrole consists of one nitrogen atom having one lone pair of electrons. Furan and thiophene have one oxygen and one sulfur heteroatom, respectively.
Basicity of Heterocyclic Aromatic Amines01:25

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).
Hybridization of Atomic Orbitals II03:35

Hybridization of Atomic Orbitals II

sp3d and sp3d 2 Hybridization
Aromatic Hydrocarbon Cations: Structural Overview01:18

Aromatic Hydrocarbon Cations: Structural Overview

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 with both...
ortho–para-Directing Activators: –CH3, –OH, –⁠NH2, –OCH301:11

ortho–para-Directing Activators: –CH3, –OH, –⁠NH2, –OCH3

All ortho–para directors, excluding halogens, are activating groups. These groups donate electrons to the ring, making the ring carbons electron-rich. Consequently, the reactivity of the aromatic ring towards electrophilic substitution increases. For instance, the nitration of anisole is about 10,000 times faster than the nitration of benzene. The electron-donating effect of the methoxy group in anisole activates the ortho and para positions on the ring and stabilizes the corresponding...
[3,3] Sigmatropic Rearrangement of 1,5-Dienes: Cope Rearrangement01:21

[3,3] Sigmatropic Rearrangement of 1,5-Dienes: Cope Rearrangement

The Cope rearrangement is classified as a [3,3] sigmatropic shift in 1,5-dienes, leading to a more stable, isomeric 1,5-diene. The reaction involves a concerted movement of six electrons, four from two π bonds and two from a σ bond, via an energetically favorable chair-like transition state.

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Related Experiment Video

Updated: Jul 3, 2026

Microwave-Assisted Preparation of 1-Aryl-1H-pyrazole-5-amines
05:07

Microwave-Assisted Preparation of 1-Aryl-1H-pyrazole-5-amines

Published on: June 23, 2019

Small band gap oligothieno[3,4-b]pyrazines.

Bram P Karsten1, René A J Janssen

  • 1Molecular Materials and Nanosystems, Eindhoven University of Technology, P.O. Box 513, NL-5600 MB Eindhoven, The Netherlands.

Organic Letters
|July 23, 2008
PubMed
Summary

Thiophene end-capped oligo(2,3-alkylthieno[3,4-b]pyrazine)s were synthesized. Their optical and electrochemical properties reveal a small band gap (1.13 eV) p-type semiconductor behavior, suitable for electronic applications.

Area of Science:

  • Organic electronics
  • Polymer science
  • Materials chemistry

Background:

  • Thieno[3,4-b]pyrazine derivatives are promising organic semiconductor materials.
  • Tuning electronic properties through controlled synthesis is crucial for advanced applications.

Purpose of the Study:

  • To synthesize thiophene end-capped oligo(2,3-alkylthieno[3,4-b]pyrazine)s.
  • To investigate the impact of chain length on their optical and electrochemical characteristics.
  • To determine the material's potential as a p-type semiconductor.

Main Methods:

  • Chemical synthesis of oligo(2,3-alkylthieno[3,4-b]pyrazine)s with varying chain lengths.
  • Optical absorption spectroscopy to analyze electronic transitions.
  • Electrochemical measurements to determine redox potentials and energy levels.

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Preparation of N-(2-alkoxyvinyl)sulfonamides from N-tosyl-1,2,3-triazoles and Subsequent Conversion to Substituted Phthalans and Phenethylamines
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Preparation of N-(2-alkoxyvinyl)sulfonamides from N-tosyl-1,2,3-triazoles and Subsequent Conversion to Substituted Phthalans and Phenethylamines

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Synthesis of pH Dependent Pyrazole, Imidazole, and Isoindolone Dipyrrinone Fluorophores using a Claisen-Schmidt Condensation Approach
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Synthesis of pH Dependent Pyrazole, Imidazole, and Isoindolone Dipyrrinone Fluorophores using a Claisen-Schmidt Condensation Approach

Published on: June 10, 2021

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Last Updated: Jul 3, 2026

Microwave-Assisted Preparation of 1-Aryl-1H-pyrazole-5-amines
05:07

Microwave-Assisted Preparation of 1-Aryl-1H-pyrazole-5-amines

Published on: June 23, 2019

Preparation of N-(2-alkoxyvinyl)sulfonamides from N-tosyl-1,2,3-triazoles and Subsequent Conversion to Substituted Phthalans and Phenethylamines
10:42

Preparation of N-(2-alkoxyvinyl)sulfonamides from N-tosyl-1,2,3-triazoles and Subsequent Conversion to Substituted Phthalans and Phenethylamines

Published on: January 3, 2018

Synthesis of pH Dependent Pyrazole, Imidazole, and Isoindolone Dipyrrinone Fluorophores using a Claisen-Schmidt Condensation Approach
14:11

Synthesis of pH Dependent Pyrazole, Imidazole, and Isoindolone Dipyrrinone Fluorophores using a Claisen-Schmidt Condensation Approach

Published on: June 10, 2021

Main Results:

  • Synthesized thiophene end-capped oligo(2,3-alkylthieno[3,4-b]pyrazine)s.
  • Observed a red shift in optical absorption with increasing chain length.
  • Attributed the shift to simultaneous rise in Highest Occupied Molecular Orbital (HOMO) and lowering of the Lowest Unoccupied Molecular Orbital (LUMO) levels.
  • Determined an optical band gap of 1.13 ± 0.07 eV.
  • Extrapolated redox potentials indicated p-type semiconductor behavior.

Conclusions:

  • The synthesized polymers exhibit tunable optical properties based on chain length.
  • The materials possess a small optical band gap and demonstrate p-type semiconducting characteristics.
  • These findings suggest potential applications in organic electronic devices.