Molecular Concepts: Polarity, Bonding, and Sketching

Vocabulary flashcards covering polarity, bonding types (hydrogen and van der Waals), and molecule sketching shorthand from the lecture.

Hydrophobic

Repels or does not mix with water; associated with nonpolar molecules.

Hydrophilic

Attracted to water; associated with polar molecules and can form hydrogen bonds with water.

Polar molecule

A molecule with an uneven distribution of electron density, leading to partial charges; often contains electronegative atoms like oxygen or nitrogen.

Nonpolar molecule

A molecule with an even distribution of electrons; little to no partial charges; often hydrocarbon-based.

Electronegativity

The tendency of an atom to attract electrons in a chemical bond (higher for O and N).

Oxygen as polarity indicator

Presence and arrangement of oxygen atoms help determine polarity; more distributed oxygens generally increase polarity; clustering can create localized polar regions.

Hydrogen bond

A weak attraction between polar molecules where a partially positive hydrogen is attracted to a highly electronegative atom (usually O or N) in another molecule; requires proximity and polarity.

Van der Waals forces

Very weak, temporary attractions between nonpolar molecules or nonpolar regions when they come very close together; depend on the number of contact points and proximity.

Proximity and randomness in Van der Waals

These forces rely on extremely close approach and the occasional random distribution of electrons; the more contacts, the stronger the cumulative effect.

Gecko adhesion (Van der Waals)

Geckos stick to walls via millions of tiny hairs creating numerous Van der Waals contacts; adhesion is strong yet easily released by reducing contact.

Oleic acid

A fatty acid with one carbon–carbon double bond; has two oxygen atoms in a carboxyl end; overall mostly nonpolar with a polar end.

Linoleic acid

A fatty acid with two carbon–carbon double bonds in the middle of the chain; more unsaturated than oleic acid.

Carbon skeleton / carbon backbone

The arrangement of carbon atoms in a molecule; shorthand representations may omit hydrogens; hydrogens are implied.

Line-angle (skeletal) formula

A shorthand molecular drawing where lines and corners represent carbon atoms and their bonds; hydrogens are usually omitted and implied.

Carbon-only formula

A representation showing only carbon and non-hydrogen atoms; hydrogens are not drawn and are implied by standard valence.

Point-and-angle method

A drawing shorthand where each point or angle represents a carbon atom; heteroatoms (e.g., O, N) are shown as letters.

Double bond

A bond formed by sharing two pairs of electrons between two atoms (e.g., C=C); affects saturation and shape; oleic acid has one, linoleic has two.

Hydrogen implied in sketches

In carbon/hydrogen skeletal formulas, hydrogen atoms are not drawn but are assumed to be present to fulfill four bonds for carbon.