General Types of Organic Reactions

Organic Chemistry

** Like other compounds, organic molecules undergo acid–base and oxidation–reduction reactions.

** Organic molecules also undergo substitution, elimination, and addition reactions..

(1) Substitution Reactions

** Substitution is a reaction in which an atom or a group of atoms is replaced by another atom or group of atoms.

** In a general substitution reaction, Y replaces Z on a carbon atom.

** Substitution reactions involve σ bonds: one δ bond breaks and another forms at the same carbon atom.

** The most common examples of substitution occur when Z is hydrogen or a heteroatom that is more electronegative than carbon.

Examples of Elimination Reactions

[1] Nucleophilic substitution at an sp³ hybridized carbon atom

[2] Nucleophilic acyl substitution at an sp² hybridized carbon atom

[3] Radical substitution at an sp³hybridized C – H bond

[4] Electrophilic aromatic substitution

(2) Elimination Reactions

** Elimination is a reaction in which elements of the starting material are “lost” and a π bond is formed.

** In an elimination reaction, two groups X and Y are removed from a starting material. Two σ bonds are broken, and a π bond is formed between adjacent atoms.

** The most common examples of elimination occur when X = H and Y is a heteroatom more electronegative than carbon.

Examples of Substitution Reactions:

β Elimination at an sp³ hybridized carbon atom

(3) Addition Reactions

** Addition is a reaction in which elements are added to a starting material.

** In an addition reaction, new groups X and Y are added to a starting material. A π bond is broken and two σ bonds are formed.

**Addition and elimination reactions are exactly opposite. A π bond is formed in elimination reactions, whereas a π bond is broken in addition reactions.