Organic Chemistry MCAT Practice Exam

What is the primary effect of resonance stabilization in organic compounds?

1. Delocalization of electrons

2. Formation of saturated compounds

3. Increase in acidity of compounds

4. Reduction in molecular weight

The correct answer is: Delocalization of electrons

Resonance stabilization primarily involves the delocalization of electrons across multiple atoms in a molecule, which leads to increased stability. This delocalization occurs when there are multiple valid Lewis structures, or resonance structures, for a single compound. Instead of being localized between two atoms, electrons in certain bonds (typically π electrons) can be thought of as being spread out or shared across several atoms. In practical terms, resonance can significantly affect the properties of a molecule, such as its reactivity and stability. For instance, in structures where resonance is significant, like benzene or carboxylate ions, this delocalization results in lower energy configurations compared to structures that do not engage in resonance. As a result, these compounds are usually more stable than their non-resonating counterparts. The other options provided relate to different aspects of molecular characteristics. While resonance can influence acidity, the primary function and definition of resonance stabilization relates directly to the delocalization of electrons. Similarly, saturation is a property of organic compounds concerning the number of hydrogen atoms in relation to the carbon backbone and is not a direct outcome of resonance. Additionally, resonance stabilization does not inherently reduce molecular weight; rather, it pertains to how electron density is distributed within the molecule.