Let's classify each reaction step-by-step:
1. For the reaction:
[tex]\[
CH_3CHO + H_2O \rightarrow CH_3OCH_3
\][/tex]
In this reaction, two molecules (CH_3CHO and H_2O) combine to form one product (CH_3OCH_3). This type of reaction where two or more molecules combine to form a single product is known as an addition reaction.
Classify as: addition
2. For the reaction:
[tex]\[
CH_2ClCH_2Cl + Zn \rightarrow C_2H_4 + ZnCl_2
\][/tex]
Here, a molecule (CH_2ClCH_2Cl) loses atoms or groups (in this case, chlorine atoms) with the assistance of Zn to form a simpler molecule (C_2H_4). Such a reaction where a single molecule splits into two simpler products is called an elimination reaction.
Classify as: elimination
3. For the reaction:
[tex]\[
CH_3CH_3Br + OH^- \rightarrow CH_3CH_3OH + Br^-
\][/tex]
In this reaction, a bromine atom from CH_3CH_3Br is replaced by a hydroxyl group (OH^-) to form CH_3CH_3OH and Br^-. This type of reaction where one atom or a group of atoms is replaced by another atom or group is known as a substitution reaction.
Classify as: substitution
4. For the reaction:
[tex]\[
2 CH_3COOH \rightarrow (CH_3CO)_2O + H_2O
\][/tex]
Here, two molecules of acetic acid (CH_3COOH) combine to form acetic anhydride ((CH_3CO)_2O) and water (H_2O). This type of reaction, where two molecules combine to form a larger molecule with the release of a small molecule like water, is called a condensation reaction.
Classify as: condensation
Thus, the classifications are:
[tex]\[
\begin{align*}
\boxed{\text{addition}}, & \quad CH_3CHO + H_2O \rightarrow CH_3OCH_3 \\
\boxed{\text{elimination}}, & \quad CH_2ClCH_2Cl + Zn \rightarrow C_2H_4 + ZnCl_2 \\
\boxed{\text{substitution}}, & \quad CH_3CH_3Br + OH^- \rightarrow CH_3CH_3OH + Br^- \\
\boxed{\text{condensation}}, & \quad 2 CH_3COOH \rightarrow (CH_3CO)_2O + H_2O \\
\end{align*}
\][/tex]
