Reactions on the pyridine substituents

What are reactions on the pyridine substituents? The reactions on pyridine substituents are those that instead of taking place on the same ring of the heterocycle, take place on the substituents of the ring producing an functional group interconversion (FGI). Reactions on alkyl groups These alkyl groups undergo the same reactions as those attached to … Read more

Reaction mechanisms

What is the mechanism of a chemical reaction? The reaction mechanism is the detailed step-by-step description of the transformation of reactants into the corresponding products in a chemical reaction. The description should include the movement of electrons that takes place by means of curved arrows, the formal charge associated with the atoms involved in the … Read more

Pericyclic reactions

What are pericyclic reactions? Pericyclic reactions are concerted reactions in a single step (therefore they are not radical reactions involving several steps), and as the name indicates, they occur in a process in which the transition state presents a closed loop of interacting electrons, so that the shape of this loop implies special characteristics of … Read more

Applications of pericyclic reactions

Introduction In the following, pericyclic reactions are described from an applications point of view. That is, we will see practical examples of these reactions aimed at demonstrating that pericyclic reactions occur and preferentially versus the non-pericyclic alternative. Moreover, it is approached from an experimental and not a theoretical point of view. We try to obtain … Read more

Cheletropic reactions and group transfer reactions

What are cheletropic reactions and group transfer reactions? They are cycloaddition reactions, however, one of the systems involved is an atom. Normally these reactions are observed in cases of cycloreversion rather than cycloaddition reactions. For example, in this reaction an orbital with a pair of sulfur electrons is involved and so this is actually a … Read more

Cycloaddition reactions

What are cycloaddition reactions? In cycloaddition reactions, as the name implies, a cyclic system is generated from the various components.  They are usually named with numbers indicating the π electrons of each component. An example would be the two ethylene molecules to form cyclobutane: This reaction would be a case of a 2+2 reaction, since one … Read more

Electrocyclic reactions

What are electrocyclic reactions? Electrocyclic reactions are characterized by the opening or closing of a ring within a single molecule by interconversion of σ bonds into π or vice versa. Typical examples of electrocyclic reactions are: This would be an allyl cation delocalized between the three centers. Where we can also make a simile of … Read more

Sigmatropic Rearrangements

They are characterized by a bond migrating along a p-system to another position in the molecule.  Thus, the nomenclature proposed by Woodward-Hoffmann for sigmatropic transposition reactions uses two numbers in square brackets indicating the positions to which the ends of the s-bond migrate. Suppose the transposition of an R group, where the C-R bond migrates along … Read more

1,3-dipolar Reactions

What are 1,3-dipolar reactions? A 1,3-dipole is a system of 3 atoms with 4 π electrons delocalized on those 3 atoms. 1,3-dipolar species cannot be written as resonant Lewis structures without using charges. That is, the Lewis structure contains only paired electrons. These 1,3-dipoles contain a central heteroatom, which may have sp or sp2 hybridization, depending on whether or not it presents a double bond orthogonal to the delocalized π-system. fig-57 … Read more

Electrochemical Batteries (Galvanic Batteries)

The electronic exchange that occurs in an oxidation-reduction reaction is used to establish devices that convert the energy released in a REDOX process into electrical energy. These devices are called galvanic cells or electrochemical cells. A battery is established when the oxidation and reduction processes occur in separate compartments, linked only by a conducting wire … Read more