Search Results
Subject - Organic Chemistry
Halogenation is a chemical reaction that incorporates halogen atoms into an organic molecule or that transforms an element into a halogen.
The most important reactions for the incorporation of halogen atoms into organic compounds are additions and substitutions. Unsaturated molecules can add halogens or hydrogen halides.
Hydrogen atoms can be substituted with fluorine, chlorine or bromine by using radical reactions, for example by photodissociation of chlorine or bromine to generate halogen atoms. In aliphatic chains, functional groups, such as OH, can be substituted with a halide (nucleophilic substitution). Decomposition of phenyldiazonium halides with loss of nitrogen allows for the introduction of any halogen into benzene rings. Chlorine and bromine can also be introduced into benzene rings by using ferric chloride as catalyst (electrophilic aromatic substitution). Using electrofluorination (anodic fluorination in anhydrous hydrofluoric acid), perfluorinations (exchange of all hydrogen atoms with fluorine) are possible.
Recommended Learning Units
HX Addition to Alkynes
10 min.
ChemistryOrganic ChemistryAlkynes
This learning unit starts with a short introduction to the family of alkynes. Then the addition of HX to alkynes in comparison with the HX addition to alkenes and the halogenation of alkynes are described.
Halogenation of Alkanes30 min.
ChemistryOrganic ChemistryRadical Reactions
This learning unit describes the principles, kinetics, and thermodynamics of the radical halogenation of alkanes and it explains the reasons for the different chemical properties of the halogens fluorine, chlorine, bromine, and iodine in radical substitution reactions.
Radical Additions and Substitutions with Alkenes40 min.
ChemistryOrganic ChemistryRadical Reactions
This learning unit describes the radical addition and radical substitution with alkenes. The mechanisms, thermodynamics, kinetics as well as the different reactivity and selectivity of several reagents and the special characterisitcs of benzylic and allylic positions are explained.
Introduction to the Reactions of Enols and Enolates30 min.
ChemistryOrganic ChemistryKeto-Enol Tautomerism
The learning unit describes various reactions of enols and enolates, such as racemization, alkylation, and halogenation.
Reactions of Aromatic Compounds (overall)90 min.
ChemistryOrganic ChemistryAromatic Chemistry
First, the learning unit describes the mechanism of electrophilic aromatic substitution including the energetics, intermediates, and transition states. Further, it is discussed in which way the inductive and mesomeric effects of first substituents influence the reactivity of substituted aromatic compounds in second substitution. Then, the nucleophilic aromatic substitution's mechanism is explained inclusive of intermediates, transition states, etc.. Finally, the preparation and the structure of dehydroarenes (arynes) is depicted.
Reactions of Aromatic Compounds - Examples of Ar-SE Reaction30 min.
ChemistryOrganic ChemistryAromatic Chemistry
The learning unit describes some important examples of electrophilic aromatic substitution, such as nitration, sulfonation, halogenation, Friedel-Crafts alkylation, Friedel-Crafts acylation, diazotization, and diazo coupling.