See image — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

# Solution: Ionization of Carboxylic Acids in Water **Key Principle:** Carboxylic acids ionize as $RCOOH \rightarrow RCOO^- + H^+$. The degree of ionization depends on **acid strength**, which is determined by the stability of the conjugate base ($RCOO^-$). **How to Increase Acid Strength:** Electron-withdrawing groups (EWGs) like $Cl$ stabilize the negative charge on $RCOO^-$ through inductive effects, making the acid more likely to ionize. **Analysis of Each Option:** | Option | Structure | $Cl$ Position | Effect | |--------|-----------|---------------|--------| | (1) | $CH_3CH_2CHClCOOH$ | 1 carbon away from $COOH$ | Weak EWG effect | | **(2)** | $CH_3CH_2CCl_2COOH$ | **Adjacent to $COOH$ with 2 $Cl$** | **Strong EWG effect** | | (3) | $CH_3CHClCH_2COOH$ | 2 carbons away from $COOH$ | Very weak effect | | (4) | $CH_2ClCH_2CH_2COOH$ | 3 carbons away from $COOH$ | Negligible effect | **Why Option (2) is Correct:** The **two chlorine atoms directly adjacent to the carboxyl group** create the strongest electron-withdrawing inductive effect, maximizing stabilization of the $-COO^-$ anion. This makes $CH_3CH_2CCl_2COOH$ the strongest acid, causing it to ionize most extensively in water. **Answer: (2)**