Difference Between Addition Reactions and Substitution Reactions

Main Difference

The main difference between addition reactions and substitution reactions is that addition reactions define as the reactions which require two or more reactants or functional groups, whereas the substitution reactions define as the reactions which comprise the replacement of a functional group or an atom with the other functional group or an atom.

Addition Reactions vs. Substitution Reactions

Addition reactions refer to the presence of more than two functional groups or reactants, whereas the substitution reactions refer to the replacement of a functional group or an atom with the other functional group or an atom. In addition reactions, there is no by-product produced, whereas, in substitution reactions, there is always by-product produced. In addition reactions, there is no leaving group, whereas in substitution reactions, the leaving group act as a by-product. In addition reactions, the molar mass of the product is always greater than the molar masses of the reactants, whereas, in substitution reactions, the molar mass of the product may or may not be greater than the molar masses of the reactants. In addition reactions, the molar masses of the product depend upon the molar mass of the reactants, whereas in substitution reactions, molar masses of the product depend upon the molar mass of the substituted group. In addition reaction, the number of bonds in adduct is less than the number of bonds in reactants, whereas, in substitution reactions, the number of bonds in product and reactants remains the same. In addition reactions, it is necessary that the reactants must have unsaturation, whereas, in substitution reactions, it is not necessary that the reactants must have unsaturation. In addition reactions, reactants must have a double or a triple bond, whereas, in substitution reactions, reactants must not have a double or triple bond.

Comparison Chart

Addition ReactionsSubstitution Reactions
Addition reactions defined as the reactions which require two or more reactants or functional groups.Substitution reactions defined as the reactions which comprise the replacement of a functional group or an atom with the other functional group or an atom.
By-Product
No by-productBy-product always formed
Molar Masses
Molar masses of the product was always greater than the reactants.Molar masses of the product may or may not be greater than the reactants.
Multiple Bonds
Must have a double or triple bondMust not have a double or triple bond
Number of Bonds of Product
Number of bonds of the product always less than reactantsNumber of bonds of products not vary
Examples
Halogenation, hydrogenation, free radical mechanism, etc.Electrophilic substitution, Nucleophilic substitution, etc.

What are Addition Reactions?

Addition reactions are reactions define as the type of reactions that always require the presence of more than the two reactants or functional groups. These reactant and functional groups add to each other to produce an adduct which is the result of the addition of both of the reactants. Addition reactions involve the presence of multiple bonds. The multiple bonds such as double bond and triple bond must present in the reactants. There is no by-product formed during the whole process. In fact, there is also no leaving group in the addition reactions. The molar masses of the product are always greater than the molar masses of the reactants. It is because of the product formed by the addition of both of the reactants. The number of bonds of the product is always less than the number of bonds of the reactants. It is necessary that the reactants must have the unsaturation. The functional groups are actually involved in the formation of the addition product.

Classification

  • Electrophilic Addition
  • Nucleophilic Addition
  • Free Radical Addition, etc

What are Substitution Reactions?

Substitution reactions are the type of reactions that refer to the replacement of a functional group or an atom with the other functional group or an atom. In this process, the nucleophile attacks the substrate molecule and replace the leaving group as a product. In this process, the leaving group leaves the substrate molecule as a by-product. In substitution reactions, it is not necessary that the reactants must have multiple bonds such as a double bond or a triple bond. The presence of unsaturation is not necessary for substitution reactions. The by-product formed during the whole process. The molar mass of the product is may or may not be greater than the reactants. The molar masses of the product always mainly depend on the substituted product. The number of bonds of the products is nearly equal to the number of bonds reactants.

Classification

  • Electrophilic Substitution
  • Nucleophilic Substitution
  • Radical substitution, etc

Key Differences

  1. Addition reactions are the type of reactions which define as the combination of more than two functional groups, whereas the substitution reactions are the type of reactions which define as the replacement of a functional group or an atom with the other functional group or an atom.
  2. In addition reactions, no by-product formed, whereas, in substitution reactions, by-product always formed.
  3. In addition reactions, reactants must have multiple bonds, whereas, in substitution reactions, reactants must not have multiple bonds.
  4. In addition reactions, the number of bonds in the product is less than the number of bonds in reactants, whereas, in substitution reactions, the number of bonds in the product is equal to the number of bonds in reactants.
  5. In addition reactions, reactions do not have a leaving group, whereas, in substitution reactions, reactions have a leaving group as a by-product.
  6. In addition reactions, the molar mass of the product is always greater than the molar masses of reactants, whereas, in substitution reactions, the molar mass of product may or may not be greater than the reactants

Conclusion

The above discussion concludes that both addition reactions and substitution reactions are types of chemical reactions. Addition reactions define as the reactions which require the presence of more than two functional groups in reactants, whereas the substitution reactions are a type of reactions which define as the replacement of an atom or a functional group with the other atom or functional group.

Harlon Moss

Harlon currently works as a quality moderator and content writer for Difference Wiki. He graduated from the University of California in 2010 with a degree in Computer Science. Follow him on Twitter @HarlonMoss

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