Organic Chemistry Acidity and Base Stability Review

Flashcards covering core organic chemistry concepts including pKa, acid-base equilibrium, halide trends, resonance vs induction, hybridization s-character, and conjugate base stability.

Direction of Reaction Equilibrium

Chemical reactions shift from the stronger acid and stronger base side to the weaker acid and weaker base side (from lower $pKa$ to higher $pKa$, or from less stable to more stable side).

$pKa$ and Acid Strength

An inverse relationship where a lower $pKa$ value indicates a stronger acid, and a higher $pKa$ value indicates a weaker acid.

Halide Size and Stability

As atomic size and surface area increase down the halogen group (e.g., iodine larger than fluorine), atom density decreases, making the resulting halide ion more stable and its corresponding acid (such as $HI$) stronger.

Resonance vs. Induction

Resonance stabilization of a conjugate base is a significantly more powerful effect on increasing acidity compared to induction.

Induction Stabilization

The stabilization of a negative charge on an anion (such as an $O^-$) through neighboring electronegative atoms (like bromine).

$sp^3$ Hybridization s-Character

A hybrid orbital composition containing one part s orbital and three parts p orbital, yielding $25\%$ s-character.

$sp^2$ Hybridization s-Character

A hybrid orbital composition containing one part s orbital and two parts p orbital, yielding $33\%$ s-character.

$sp$ Hybridization s-Character

A hybrid orbital composition containing one part s orbital and one part p orbital, yielding $50\%$ s-character.

s-Character and Base Stability Rule

Higher percent s-character ($sp$ at $50\%$ > $sp^2$ at $33\%$ > $sp^3$ at $25\%$) holds the lone pair closer to the positively charged nucleus, rendering the conjugate base more stable and its corresponding acid stronger.

Conjugate Base Stability Rule

The core principle that the more stable the conjugate base ($A^-$), the stronger its corresponding conjugate acid ($HA$).