Answered

Classify each of these as an addition, substitution, elimination, or condensation reaction:


  1. $CH_3CHO + H_2O \rightarrow CH_3OCH_3$
  2. $CH_2ClCH_2Cl + Zn \rightarrow C_2H_4 + ZnCl_2$
  3. $CH_3CH_3Br + OH^{-} \rightarrow CH_3CH_3OH + Br^{-}$
  4. $2CH_3COOH \rightarrow (CH_3CO)_2O + H_2O$

Verified Answer :

  • The reaction \(CH_3CHO + H_2O \rightarrow CH_3OCH_3\) is an addition reaction.
  • The reaction \(CH_2ClCH_2Cl + Zn \rightarrow C_2H_4 + ZnCl_2\) is an elimination reaction.
  • The reaction \(CH_3CH_3Br + OH^{-} \rightarrow CH_3CH_3OH + Br^{-}\) is a substitution reaction.
  • The reaction \(2CH_3COOH \rightarrow (CH_3CO)_2O + H_2O\) is a condensation reaction.

Explanation

  1. Analysis of Chemical Reactions

To classify chemical reactions, we examine the changes in molecular structure, the bonds formed or broken, and the types of products produced.

  1. Reaction: \(CH_3CHO + H_2O \rightarrow CH_3OCH_3\). This reaction involves the combination of two reactant molecules into a single product molecule. This is characteristic of an addition reaction, where multiple reactants join together to form a single larger molecule.
  2. Reaction: \(CH_2ClCH_2Cl + Zn \rightarrow C_2H_4 + ZnCl_2\). In this process, the chlorine atoms are removed from the 1,2-dichloroethane molecule, leading to the formation of a carbon-carbon double bond (\(C_2H_4\), ethene). The removal of atoms or groups of atoms to create a double bond is defined as an elimination reaction.
  3. Reaction: \(CH_3CH_3Br + OH^{-} \rightarrow CH_3CH_3OH + Br^{-}\). Here, the bromine atom (a leaving group) is directly replaced by the hydroxide ion. This exchange of functional groups where one atom or group is replaced by another is a classic substitution reaction.
  4. Reaction: \(2CH_3COOH \rightarrow (CH_3CO)_2O + H_2O\). This reaction shows two molecules of acetic acid joining to form a single anhydride molecule, while a water molecule is lost as a byproduct. The formation of a larger molecule accompanied by the loss of a small molecule like water is classified as a condensation reaction.

Examples

The classification of chemical reactions is fundamental in synthetic chemistry, helping chemists predict how molecules will behave in a laboratory setting. For instance, pharmaceutical companies use these classifications to design efficient pathways for creating complex medicine molecules. Understanding whether a reaction is an addition or a substitution helps researchers choose the right catalysts and conditions to maximize yield, effectively turning raw starting materials into valuable products like antibiotics or life-saving therapies.

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