Theoretical Basis of Reactions

Principles of Organic Chemistry begins by exploring the step-by-step processes (or mechanisms) by which reactions occur to create molecular structures, using clear and consistently coloured figures. It then examines functional groups and the corresponding common reaction mechanisms to describe some of the many ways these reactions create new compounds.

Furthermore, in organic chemistry, reaction mechanisms are classified into four types: substitution 1 (Sn1), substitution 2 (Sn2), elimination 1 (E1), and elimination 2 (E2).

The applications of various experimental techniques in the elucidation of reaction details, as well as the development of various computational techniques to meet the demand of emerging synthetic methods, such as C–H activation, organocatalysis, and single electron transfer, are discussed, along with some conventional developments of mechanistic aspects.

What is Chemical Reaction?

A chemical reaction is a process that converts one or more compounds, known as reactants, into one or more distinct substances, known as products. Various substances can be characterised as chemical elements or compounds.

Chemical reactions are an essential aspect of technology, society, and life itself. Many activities involving chemical reactions that have been understood and practised for thousands of years include burning fuels, smelting iron, creating glass and pottery, brewing beer, and making wine and cheese. Chemical reactions exist in Earth’s geology, the atmosphere and seas, and a wide range of complex processes that occur in all biological systems.

Principle of Organic Chemistry

Let’s start with the fundamental principles of organic chemistry that are quite important when working with chemical processes.

Nucleophiles

Nucleophiles are reagents that are either negatively charged or carry a lone pair of electrons. These reagents draw protons or positive charges to themselves.

Electrophiles

Electrophiles are positively charged reagents that require electrons to stabilise them.

Electromeric Effect

 In this effect, electrons are completely transferred to one of the atoms that are directly bonded with numerous bonds. This impact is only seen in many bonds. It is only active during the reagent assault and is only active for a short period of time.

Inductive Effect

The inductive effect occurs when two distinct atoms with differing electronegativities are linked together. The bound electrons are moved towards the more electronegative atom in this situation, resulting in the polar covalent bond. When electrons migrate towards carbon, this is known as the +I effect, and when electrons shift away from carbon, it is known as the -I effect. The relative inductive effect series is as follows, based on the intensity of the -I effect:

–NH₃+ > –NO₂ > –SO₂R > –CN > –SO₃H > –CHO > –CO > –COOH > –F > –COCl > –CONH₂ > –Cl > –Br > –I > –OR > –OH > –NR2 > –NH₂ > –C₆H₅ > –CH=CH₂

Resonance Effect

The polarity induced in a molecule by the interaction of a lone pair of electrons and a pi bond, or by the interaction of two pi bonds between two nearby atoms, is known as the resonance effect. The resonance effect can be observed in molecules with conjugated double bonds or molecules with at least one lone pair of electrons and one double bond.

(i) Positive resonance effect (+R effect): The electrons in this action are displaced away from the substituted group connected to the conjugated system.

(ii) Negative resonance effect (-R effect): In this effect, electrons are pushed towards the substituted group linked to the conjugated system.

Hyperconjugation

In this effect, sigma-electrons are delocalized to the unsaturated system or unshared p-orbital. This impact is permanent.

What is Exothermic Reaction?

In chemistry Many chemical reactions produce heat, light, and sound as a by-product. This is an exothermic process. Exothermic reactions can occur spontaneously and increase the system’s unpredictability or entropy (ΔS > 0). They are distinguished by a drop in enthalpy (ΔH < 0) and a negative heat flow (heat is lost to the environment). Exothermic reactions in the lab generate heat and may even be explosive.

What is Endothermic Reaction?

Endothermic reactions are chemical processes in which the reactants absorb heat energy from their environment in order to produce products. These reactions reduce the temperature of their surroundings, resulting in a cooling effect. Endothermic processes can occur in physical processes as well. For example, ice cubes absorb heat energy from their surroundings and melt to become liquid water (no chemical bonds are broken or formed).

When a chemical connection is broken, it typically results in the release of energy. Similarly, the creation of chemical bonds necessitates the use of energy. The energy supplied/released can take several forms (such as heat, light, and electricity). Endothermic reactions are characterised by the creation of chemical bonds as a result of heat absorption from the environment.

Conclusion

The applications of various experimental techniques in the elucidation of reaction details, as well as the development of various computational techniques to meet the demand of emerging synthetic methods, such as C-H activation, organocatalysis, and single electron transfer, are discussed, along with some conventional developments of mechanistic aspects. A chemical reaction rearranges the constituent atoms of the reactants to produce various products. The resonance effect can be observed in molecules with conjugated double bonds or molecules with at least one lone pair of electrons and one double bond. When a chemical connection is broken, it typically results in the release of energy. Organic chemistry is the study of the structure, characteristics, and interactions of organic molecules that include carbon in covalent bonds.