Functional Groups in Pharmacy: Bonding, Aromaticity, and Acid-Base Properties

Flashcards covering chemical bonding types, criteria for aromaticity, Brønsted-Lowry acid-base mechanisms, and acid/base behavior of specific nitrogen-containing aromatic functional groups.

Covalent Bond

A type of bonding where electrons ($e^-$) are shared with itself to complete the octet rule.

Ionic Bond

A type of bonding where an atom steals or donates electrons ($e^-$), such as between $Na^+$ and $F^-$.

Hydrogen Bond

A dipole-dipole interaction where electrons are pulled toward strongly electronegative elements ($N$, $O$, $F$).

Van der Waals Interactions

Dipole-dipole interactions that make molecular interactions asymmetrical.

Aromaticity

A molecular property requiring a cyclic, planar, conjugated system with $4n + 2$$\pi$ electrons.

Brønsted-Lowry Acid

A chemical species that acts as a $H^+$ donor and becomes a conjugate base.

Brønsted-Lowry Base

A chemical species that acts as a $H^+$ acceptor and becomes a conjugate acid.

Resonance Stabilization of Heteroatom Conjugate Base

Delocalization of negative charge through resonance lowers energy and enthalpy; Oxygen requires $\ge 2$ resonance forms while Nitrogen requires $\ge 3$ resonance forms for effective stabilization.

Basic Functional Group

A functional group featuring a Nitrogen atom with a localized lone pair of electrons ($e^-$).

Neutral Functional Group

A functional group that displays neither acidic nor basic properties.

Aniline

A weakly basic molecule whose Nitrogen lone pair is shared with the aromatic ring, making it less likely to grab $H^+$, but still capable of grabbing $H^+$ rather than donating $H$.

Pyridine

A basic aromatic ring containing a double bond on N; it is not acidic because it lacks a $H$ on the heteroatom, and its lone pair is localized because it cannot physically overlap with the aromatic system without breaking conjugation.

Pyrrole

A neutral aromatic molecule with no double bond attached to N; containing $6$$\pi$ electrons ($4n + 2 = 6$, $n = 1$), it is not acidic because losing $H$ would cause it to lose aromaticity and stability.