Search research articles

ABOUT JoVE

Overview Leadership Blog JoVE Help Center

AUTHORS

Publishing Process Editorial Board Scope & Policies Peer Review FAQ Submit

LIBRARIANS

Testimonials Subscriptions Access Resources Library Advisory Board FAQ

RESEARCH

JoVE Journal Methods Collections JoVE Encyclopedia of Experiments Archive

EDUCATION

JoVE Core JoVE Business JoVE Science Education JoVE Lab Manual Faculty Resource Center Faculty Site

Terms & Conditions of Use

Related Concept Videos

Olefin Metathesis Polymerization: Ring-Opening Metathesis Polymerization (ROMP)

Olefin Metathesis Polymerization: Ring-Opening Metathesis Polymerization (ROMP)

Ring-opening metathesis polymerization or ROMP involves strained cycloalkenes as starting materials. The mechanism of ROMP proceeds by reacting cycloalkene with Grubbs catalyst to give metallacyclobutane intermediate which undergoes a ring-opening reaction to form new carbene. The new carbene reacts with another molecule of cycloalkene. Repetition of these steps leads to the formation of an unsaturated open-chain polymer product. All these steps are reversible, however, relieving the ring...

Thermal Electrocyclic Reactions: Stereochemistry

Thermal Electrocyclic Reactions: Stereochemistry

The stereochemistry of electrocyclic reactions is strongly influenced by the orbital symmetry of the polyene HOMO. Under thermal conditions, the reaction proceeds via the ground-state HOMO.
Selection Rules: Thermal Activation
Conjugated systems containing an even number of π-electron pairs undergo a conrotatory ring closure. For example, thermal electrocyclization of (2E,4E)-2,4-hexadiene, a conjugated diene containing two π-electron pairs, gives trans-3,4-dimethylcyclobutene.

Base-Catalyzed Ring-Opening of Epoxides

Base-Catalyzed Ring-Opening of Epoxides

Due to their highly strained structures, epoxides can readily undergo ring-opening reactions through nucleophilic substitution, either in the presence of an acid or a base. The nucleophilic substitution reactions in the presence of acid are called acid-catalyzed ring-opening reactions, and nucleophilic substitution reactions in the presence of a base are called base-catalyzed ring-opening reactions. Epoxides undergo base-catalyzed ring-opening reactions in the presence of a strong nucleophile...

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

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...

Acid-Catalyzed Ring-Opening of Epoxides

Acid-Catalyzed Ring-Opening of Epoxides

Epoxides that are three-membered ring systems are more reactive than other cyclic and acyclic ethers. The high reactivity of epoxides originates from the strain present in the ring. This ring strain acts as a driving force for epoxides to undergo ring-opening reactions either with halogen acids or weak nucleophiles in the presence of mild acid. The acid catalyst converts the epoxide oxygen, a poor leaving group, into an oxonium ion, a better leaving group, making the reaction feasible. The...

Olefin Metathesis Polymerization: Overview

Olefin Metathesis Polymerization: Overview

Recently, the development of olefin metathesis polymerization advanced the field of polymer synthesis. Simply put, the reorganization of substituents on their double bonds between two olefins in the presence of a catalyst is known as the olefin metathesis reaction. The use of metathesis reaction for polymer synthesis is called olefin metathesis polymerization.
Ruthenium-based Grubbs catalyst is the most commonly used catalyst for olefin metathesis polymerization. Grubbs catalyst consists...

You might also read

Related Articles

Articles linked to this work by shared authors, journal, and citation graph.

Sort by

Same author

Cellular prion protein suppresses colitis and colorectal carcinogenesis via modulating inflammatory responses.

Biochimica et biophysica acta. Molecular basis of disease·2026

Same author

The octapeptide repeats of prion protein play critical roles in the pathogenesis of prion diseases.

Acta neuropathologica communications·2026

Same author

Comparative Pharmacology of Caspase-1 Inhibitors: Ac-YVAD-CMK, Z-YVAD-FMK, and Ac-YVAD-CHO in Multisystem Diseases.

Medicinal research reviews·2026

Same author

Photoinitiated carboxymethyl chitosan interpenetrating network hydrogel with hydrophobic modification: Coordination geometry-driven efficient removal of Co<sup>2+</sup> and Ni<sup>2</sup>.

International journal of biological macromolecules·2026

Same author

Accelerating hybrid XOR-CNF Boolean satisfiability problems natively with in-memory computing.

Nature communications·2026

Same author

A Low-Noise, Low-Power, and Wide-Bandwidth Regulated Cascode Transimpedance Amplifier with Cascode-Feedback in 40 nm CMOS.

Sensors (Basel, Switzerland)·2026

Same journal

Multitargeted Degradation of Cell Surface Receptors by Modular Glyco-Nanosheets.

ACS macro letters·2026

Same journal

Vinyl Ether Maleic Anhydride Copolymers: Efficient and Reusable Sorbents for Removing Heavy Metals from Water.

ACS macro letters·2026

Same journal

Topology-Preserving Elastic Deformation Augmentation Enables Robust Defect Detection in Data-Scarce Industrial Imagery.

ACS macro letters·2026

Same journal

Flexible Porous Organic Polymers with α,β-Enone-Linkage via AlCl<sub>3</sub>-Catalyzed Horner-Wadsworth-Emmons Polymerization for Pd Recovery.

ACS macro letters·2026

Same journal

Light-Controlled Topology Switching Enables Continuous Modulation of Thermally Induced Phase Behavior in Polymer Solutions.

ACS macro letters·2026

Same journal

Correction to "Light-Induced Transformation from Covalent to Supramolecular Polymer Networks".

ACS macro letters·2026

See all related articles

Search research articles

Related Experiment Video

Updated: Sep 22, 2025

Controlled Photoredox Ring-Opening Polymerization of O-Carboxyanhydrides Mediated by Ni/Zn Complexes

Controlled Photoredox Ring-Opening Polymerization of O-Carboxyanhydrides Mediated by Ni/Zn Complexes

Published on: November 21, 2017

Zwitterionic Ring Opening Polymerization with Isothioureas.

Xiangyi Zhang¹, Robert M Waymouth¹

¹Department of Chemistry, Stanford University, Stanford, California 94305-5080, United States.

ACS Macro Letters

|May 25, 2022

Summary

This summary is machine-generated.

Bicyclic isothioureas enable controlled ring-opening polymerization of lactides, producing high-molecular-weight cyclic polylactides (PLA) with narrow polydispersities. These initiators offer greater selectivity for cyclic PLA compared to DBU, minimizing linear polymer formation.

More Related Videos

Photogeneration of N-Heterocyclic Carbenes: Application in Photoinduced Ring-Opening Metathesis Polymerization

Photogeneration of N-Heterocyclic Carbenes: Application in Photoinduced Ring-Opening Metathesis Polymerization

Published on: November 29, 2018

Self-assembling Morphologies Obtained from Helical Polycarbodiimide Copolymers and Their Triazole Derivatives

Self-assembling Morphologies Obtained from Helical Polycarbodiimide Copolymers and Their Triazole Derivatives

Published on: February 7, 2017

Related Experiment Videos

Last Updated: Sep 22, 2025

Controlled Photoredox Ring-Opening Polymerization of O-Carboxyanhydrides Mediated by Ni/Zn Complexes

Controlled Photoredox Ring-Opening Polymerization of O-Carboxyanhydrides Mediated by Ni/Zn Complexes

Published on: November 21, 2017

Photogeneration of N-Heterocyclic Carbenes: Application in Photoinduced Ring-Opening Metathesis Polymerization

Photogeneration of N-Heterocyclic Carbenes: Application in Photoinduced Ring-Opening Metathesis Polymerization

Published on: November 29, 2018

Self-assembling Morphologies Obtained from Helical Polycarbodiimide Copolymers and Their Triazole Derivatives

Self-assembling Morphologies Obtained from Helical Polycarbodiimide Copolymers and Their Triazole Derivatives

Published on: February 7, 2017

Area of Science:

Polymer Chemistry
Organic Synthesis
Materials Science

Background:

Ring-opening polymerization (ROP) is a key method for synthesizing polyesters like polylactide (PLA).
Controlled ROP is crucial for achieving desired polymer properties, such as high molecular weight and narrow polydispersity.
Conventional ROP often requires protic initiators or can lead to undesired linear polymer byproducts.

Purpose of the Study:

To investigate the efficacy of bicyclic isothioureas as initiators for controlled ROP of lactides.
To compare the selectivity of isothioureas with conventional initiators like DBU in PLA synthesis.
To elucidate the mechanism of isothiourea-mediated ROP and identify factors influencing cyclic vs. linear PLA formation.

Main Methods:

Ring-opening polymerization (ROP) of lactides using bicyclic isothioureas (1 and 2) as initiators.
Characterization of resulting polylactides (PLA) using dilute solution viscosity measurements and MALDI-TOF mass spectrometry.
Mechanistic studies involving acyl amidinium intermediates to understand the polymerization pathway.

Main Results:

Bicyclic isothioureas successfully mediated controlled ROP of lactides without protic initiators.
High molecular weight PLA with narrow polydispersities was obtained.
Isothioureas demonstrated superior selectivity for cyclic PLA formation compared to DBU, significantly reducing linear polymer contaminants.
Mechanistic studies supported a pathway involving ketene aminal intermediates for DBU-initiated linear chain generation.

Conclusions:

Bicyclic isothioureas are effective and selective initiators for the controlled synthesis of cyclic polylactides.
These isothioureas offer a significant advantage over DBU in producing high-purity cyclic PLA.
The findings provide valuable insights into the mechanism of lactide polymerization and the development of novel catalytic systems for polyester synthesis.