Hydroxyl radicals can pluck hydrogen atoms from molecules (“hydrogen abstraction”), and hydroxide ions can pluck protons from molecules (“deprotonation”). Write the reaction equations and Lewis dot structures for the hydrogen abstraction and deprotonation reactions for the generic carboxylic acid R¬COOH with hydroxyl radical and hydroxide ion, respectively. Why is the hydroxyl radical more toxic to living systems than the hydroxide ion?

Verified step by step guidance

1. Step 1: Identify the reactants and products for the hydrogen abstraction reaction. The hydroxyl radical (•OH) will react with the generic carboxylic acid (R-COOH) to form water (H2O) and a radical species (R-COO•).
2. Step 2: Write the balanced chemical equation for the hydrogen abstraction reaction: R-COOH + •OH → R-COO• + H2O.
3. Step 3: Draw the Lewis dot structures for the reactants and products in the hydrogen abstraction reaction. Show the unpaired electron on the hydroxyl radical and the radical site on the carboxylate radical (R-COO•).
4. Step 4: Identify the reactants and products for the deprotonation reaction. The hydroxide ion (OH-) will react with the generic carboxylic acid (R-COOH) to form water (H2O) and a carboxylate ion (R-COO-).
5. Step 5: Write the balanced chemical equation for the deprotonation reaction: R-COOH + OH- → R-COO- + H2O. Draw the Lewis dot structures for the reactants and products, showing the lone pairs on the hydroxide ion and the carboxylate ion.

Key Concepts

Hydroxyl Radical

The hydroxyl radical (•OH) is a highly reactive species with an unpaired electron, making it a potent oxidizing agent. It can initiate reactions by abstracting hydrogen atoms from organic molecules, leading to the formation of new radicals and potentially damaging cellular components. Its reactivity is a key factor in its toxicity, as it can disrupt biological processes and cause oxidative stress.

Deprotonation

Deprotonation is the process of removing a proton (H+) from a molecule, resulting in the formation of a conjugate base. In the context of carboxylic acids, deprotonation typically occurs when a hydroxide ion (OH-) interacts with the acidic hydrogen of the carboxyl group (RCOOH), producing water and the carboxylate ion (RCOO-). This reaction is fundamental in acid-base chemistry and influences the reactivity and stability of organic compounds.

Toxicity of Reactive Oxygen Species (ROS)

Reactive oxygen species (ROS), including hydroxyl radicals, are known for their ability to cause cellular damage through oxidative stress. Unlike hydroxide ions, which are relatively stable and less reactive, hydroxyl radicals can rapidly react with a wide range of biomolecules, including lipids, proteins, and DNA. This high reactivity leads to significant biological damage, contributing to the toxicity of hydroxyl radicals in living systems.