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Electrophiles

Electrophiles

This lesson explains the definition, classification, and characteristic features of an electrophile that are key features of nucleophilic substitution reactions. An analysis of their charge and orbital picture helps understand their reactivity for seeking electrons. Electrophiles can be classified into positive and neutral species. Other classes include free radicals and polar functional groups.
While a positive electrophile, like a proton, reacts due to its vacant, low-energy 1s orbital, the...

Preparation and Reactions of Thiols

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Thiols are prepared using the hydrosulfide anion as a nucleophile in a nucleophilic substitution reaction with alkyl halides. For instance, bromobutane reacts with sodium hydrosulfide to give butanethiol.

Nucleophiles

Nucleophiles

The word “nucleophile” has a Greek root and translates to nucleus-loving. Nucleophiles are either negatively charged or neutral species with a pair of electrons in a high-energy occupied molecular orbital (HOMO). As these species tend to donate electron pairs, nucleophiles are considered Lewis bases as well. Negatively charged species, like OH−, Cl−, or HS−, with one or several pairs of electrons, are typically nucleophiles. Similarly, neutral species such as...

ortho–para-Directing Deactivators: Halogens

ortho–para-Directing Deactivators: Halogens

Halogens are ortho–para directors. They are more electronegative than carbon. Therefore, as ring substituents, they can withdraw electrons through the inductive effect and deactivate the aromatic ring towards electrophilic substitution. Halogens also have an electron-donating resonance effect on the ring, which influences the orientation of the incoming electrophile. If an electrophile attacks at the ortho or the para position, the halogen donates electrons and stabilizes the intermediate...

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

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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...

Nucleophilic Substitution Reactions

Nucleophilic Substitution Reactions

Historical perspective
In 1896, the German chemist Paul Walden discovered that he could interconvert pure enantiomeric (+) and (-) malic acids through a series of reactions. This conversion suggested the involvement of optical inversion during the substitution reaction. Further, in 1930, Sir Christopher Ingold described for the first time two different forms of nucleophilic substitution reactions, which are known as SN1 (nucleophilic substitution unimolecular) and SN2 (nucleophilic substitution...

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Related Experiment Video

Updated: Dec 13, 2025

Synthesis of a Thiol Building Block for the Crystallization of a Semiconducting Gyroidal Metal-sulfur Framework

Synthesis of a Thiol Building Block for the Crystallization of a Semiconducting Gyroidal Metal-sulfur Framework

Published on: April 9, 2018

ThDione: A Powerful Electron-Withdrawing Moiety for Push-Pull Molecules.

Eva Novotná¹, Iwan V Kityk², Oldřich Pytela¹

¹Institute of Organic Chemistry and Technology, University of Pardubice, Faculty of Chemical Technology, Studentská 573, Pardubice, 53210, Czech Republic.

|July 25, 2020

Summary

New push-pull chromophores featuring a cyclopenta[c]thiophene-4,6-dione (ThDione) acceptor were synthesized. These molecules exhibit tunable electronic properties and enhanced nonlinear optical responses, demonstrating ThDione as a versatile building block.

Keywords:

(non)linear optics diones donor-acceptor systems electrochemistry thiophenes

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Last Updated: Dec 13, 2025

Synthesis of a Thiol Building Block for the Crystallization of a Semiconducting Gyroidal Metal-sulfur Framework

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Published on: April 9, 2018

Constructing Thioether/Vinyl Sulfide-tethered Helical Peptides Via Photo-induced Thiol-ene/yne Hydrothiolation

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Published on: August 1, 2018

From Molecules to Materials: Engineering New Ionic Liquid Crystals Through Halogen Bonding

From Molecules to Materials: Engineering New Ionic Liquid Crystals Through Halogen Bonding

Published on: March 24, 2018

Area of Science:

Organic Chemistry
Materials Science
Photophysics

Background:

Push-pull chromophores are crucial for nonlinear optics.
Developing novel electron-withdrawing units is essential for tuning chromophore properties.
Cyclopenta[c]thiophene-4,6-dione (ThDione) is a potential acceptor unit.

Purpose of the Study:

To design and synthesize new push-pull chromophores utilizing the ThDione acceptor.
To investigate the structure-property relationships of these novel molecules.
To evaluate the potential of ThDione as a versatile electron-withdrawing unit.

Main Methods:

Organic synthesis of linear and branched push-pull molecules.
Experimental characterization of thermal, electrochemical, and optical properties.
Theoretical calculations to elucidate electronic structure and properties.

Main Results:

Successful synthesis of chromophores with one or two ThDione acceptors.
Demonstrated thermal stability up to 260°C.
Tunable HOMO-LUMO gaps (electrochemical: 1.47-2.19 eV; optical: 1.99-2.39 eV).
Significant intramolecular charge transfer and π-system polarization.
Enhanced nonlinear optical response.

Conclusions:

ThDione is a powerful and versatile acceptor unit for push-pull chromophores.
The synthesized molecules exhibit promising properties for optical applications.
Structure-property relationships were thoroughly understood, enabling rational design.