The key difference between synthesis reaction and substitution reaction is that the synthesis reaction gives a new chemical compound formed from reactant combination, whereas the substitution reactions give a chemical compound that is derived from an existing chemical compound.
Synthesis reaction and substitution reaction are important organic synthesis reactions. Both of these reactions form chemical compounds.
CONTENTS
1. Overview and Key Difference
2. What is a Synthesis Reaction
3. What is a Substitution Reaction
4. Side by Side Comparison – Synthesis Reaction vs Substitution Reaction in Tabular Form
5. Summary
What is a Synthesis Reaction?
A synthesis reaction is a type of chemical reaction in which two or more components combine with each other to form a large compound. The synthesis reaction is the opposite of the dissociation reaction. We can call it a direct combination reaction as well because it involves the combination of components to form a new compound. Furthermore, the reactants in these reactions are either chemical elements or molecules. The final product of a synthesis reaction is always a compound or a complex.
For example, the combination of hydrogen gas and oxygen gas that forms water molecules, the combination of carbon monoxide and oxygen that forms carbon dioxide, the combination of aluminium metal and oxygen gas that forms aluminium oxide, etc.
Figure 01: Formation of a Large Chemical Compound via the Combination of Small Reactant Molecules
We can recognize a synthesis reaction via observing the end product; it is always a compound. In these reactions, all the atoms present in the reactant molecules have to be present in the end product. Moreover, during bond formation, these reactions release energy; therefore, they are exothermic reactions.
What is a Substitution Reaction?
Substitution reactions are chemical reactions in which the moieties of molecules replace the moieties of other molecules. A moiety is a part of a molecule. In these reactions, the moieties are either atoms, ions, or functional groups. Further, these reactions mostly take place by replacing a functional group of a molecule with another functional group. These chemical reactions are very important reactions in organic chemistry.
Figure 02: Substitution Reaction Mechanism for 2-Chlorobutane
Moreover, there are two types of substitution reactions as electrophilic substitution reactions and nucleophilic substitution reactions. However, there is another category as well; that is the radical substitution reaction.
What is the Difference Between Synthesis Reaction and Substitution Reaction?
Synthesis reactions and substitution reactions are important chemical reactions in organic chemistry. The key difference between synthesis reaction and substitution reaction is that the synthesis reaction gives a new chemical compound formed from a reactant combination, whereas the substitution reactions give a chemical compound that is derived from an existing chemical compound. An example of a synthesis reaction is the combination of hydrogen gas and oxygen gas to form a water molecule while an example for a substitution reaction is the electrophilic substation reaction of 2-chlorobutane.
The following infographic shows more comparisons between both reactions in order to discern the differences between synthesis reaction and substitution reaction.
Summary – Synthesis Reaction vs Substitution Reaction
Synthesis reactions and substitution reactions are important chemical reactions in organic chemistry. In summary, the key difference between synthesis reaction and substitution reaction is that the synthesis reaction gives a new chemical compound formed from reactant combination, whereas the substitution reactions give a chemical compound that is derived from an existing chemical compound.
Reference:
1. Helmenstine, Anne Marie. “Substitution Reaction Definition.” ThoughtCo, Feb. 11, 2020, Available here.
2. Helmenstine, Anne Marie. “Synthesis Reaction Description Plus Examples.” ThoughtCo, Feb. 11, 2020, Available here.
Image Courtesy:
1. “Lophine-synthesis reaction” By Adam001d at Polish Wikipedia (CC BY 3.0) via Commons Wikimedia
2. “2 chlorobutane substitution mechanism” By Ajoyce7 – Own work (CC BY-SA 4.0) via Commons Wikimedia