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Conjugate Addition to α,β-Unsaturated Carbonyl Compounds

Conjugate Addition to α,β-Unsaturated Carbonyl Compounds

α,β-Unsaturated carbonyl compounds are molecules bearing a carbonyl and alkene functionality in conjugation with each other. The conjugation in the molecule leads to three resonance structures. The hybrid form exhibits two probable electrophilic sites: the carbonyl carbon and the β carbon.

Aldehydes and Ketones with Alcohols: Hemiacetal Formation

Aldehydes and Ketones with Alcohols: Hemiacetal Formation

Similar to water, alcohols can add to the carbonyl carbon of the aldehydes and ketones. The addition of one molecule of alcohol to the carbonyl compound forms the hemiacetal or half acetal. As depicted below, in a hemiacetal, the carbon is directly linked to an OH and OR group.

Electrophilic Addition to Alkynes: Hydrohalogenation

Electrophilic Addition to Alkynes: Hydrohalogenation

Electrophilic addition of hydrogen halides, HX (X = Cl, Br or I) to alkenes forms alkyl halides as per Markovnikov's rule, where the hydrogen gets added to the less substituted carbon of the double bond. Hydrohalogenation of alkynes takes place in a similar manner, with the first addition of HX forming a vinyl halide and the second giving a geminal dihalide.

Aryldiazonium Salts to Azo Dyes: Diazo Coupling

Aryldiazonium Salts to Azo Dyes: Diazo Coupling

The reaction of weakly electrophilic aryldiazonium (also called arenediazonium) salts with highly activated aromatic compounds leads to the formation of products with an —N=N— link, called an azo linkage. This reaction, presented in Figure 1, is known as diazo coupling and occurs without the loss of the nitrogen atoms of the aryldiazonium salt. Highly activated aromatic compounds such as phenols or arylamines favor the diazo coupling reaction. The coupling generally occurs at the...

Conjugate Addition (1,4-Addition) vs Direct Addition (1,2-Addition)

Conjugate Addition (1,4-Addition) vs Direct Addition (1,2-Addition)

α,β-Unsaturated carbonyl compounds with two electrophilic sites, the carbonyl carbon, and the β carbon, are susceptible to nucleophilic attack via two modes: conjugate or 1,4-addition and direct or 1,2-addition.
Conjugate addition results in a thermodynamically stable product. The reaction retains the stronger C=O bond at the expense of the weaker C=C π bond. The process is slow as the β carbon is less electrophilic than the carbonyl carbon.
Direct addition products are...

Electrophilic Addition to Alkynes: Halogenation

Electrophilic Addition to Alkynes: Halogenation

Introduction
Halogenation is another class of electrophilic addition reactions where a halogen molecule gets added across a π bond. In alkynes, the presence of two π bonds allows for the addition of two equivalents of halogens (bromine or chlorine). The addition of the first halogen molecule forms a trans-dihaloalkene as the major product and the cis isomer as the minor product. Subsequent addition of the second equivalent yields the tetrahalide.

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Related Experiment Video

Updated: Jun 24, 2025

Efficient and Site-specific Antibody Labeling by Strain-promoted Azide-alkyne Cycloaddition

Efficient and Site-specific Antibody Labeling by Strain-promoted Azide-alkyne Cycloaddition

Published on: December 23, 2016

Conjugating Hemoglobin and Albumin by Strain-Promoted Azide- Alkyne Cycloaddition.

Chi Lee¹, Harriet Wenxin Chung¹, Ronald Kluger¹

¹Davenport Chemistry Laboratories, Department of Chemistry, University of Toronto, Toronto, Ontario, M5S 3H6, Canada.

Chembiochem : a European Journal of Chemical Biology

|June 5, 2024

Summary

Researchers created a human hemoglobin and albumin bioconjugate for oxygen delivery. This acellular oxygen carrier shows suitable oxygen binding properties for potential therapeutic applications.

Keywords:

acellular oxygen carrier albumin bioconjugation click chemistry hemoglobin protein modifications strain-promoted

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Synthesis of Protein Bioconjugates via Cysteine-maleimide Chemistry

Synthesis of Protein Bioconjugates via Cysteine-maleimide Chemistry

Published on: July 20, 2016

Area of Science:

Bioconjugation Chemistry
Biomaterials Science
Oxygen Therapeutics

Background:

Development of acellular oxygen carriers is crucial for transfusion medicine.
Cross-linked hemoglobin has shown promise but faces challenges like nitric oxide scavenging.
Human serum albumin is a biocompatible protein with potential for conjugation.

Purpose of the Study:

To create a one-to-one conjugate of human hemoglobin and human serum albumin.
To evaluate the oxygen binding properties of the resulting bioconjugate.
To assess the suitability of the bioconjugate as an acellular oxygen carrier.

Main Methods:

Utilized strain-promoted alkyne-azide cycloaddition (SPAAC) for bioconjugation.
Modified human serum albumin with a strained alkyne at Cys-34.
Modified human hemoglobin with an azide cross-linker at Lys-82.
Purified the hemoglobin-albumin conjugate using chromatography.

Main Results:

Successfully synthesized a one-to-one human hemoglobin-human serum albumin bioconjugate.
The conjugate exhibited appropriate oxygen affinity and cooperativity.
The bioconjugate could be purified from unreacted hemoglobin.

Conclusions:

The developed hemoglobin-albumin bioconjugate is a viable acellular oxygen carrier.
The SPAAC reaction provides an efficient method for creating such bioconjugates.
The oxygen transport characteristics are promising for clinical applications.