Chapter 3: Introduction to Organic Molecules and Functional Groups

Vocabulary flashcards covering key terms and definitions from Chapter 3: Introduction to Organic Molecules and Functional Groups.

Functional group

A chemically reactive group of atoms in a molecule whose chemistry largely determines the molecule's properties.

R group

A generic placeholder for the rest of a molecule (the carbon backbone) to which a functional group is attached.

Hydrocarbon

A compound composed only of carbon and hydrogen; can be aliphatic or aromatic.

Aliphatic hydrocarbon

Hydrocarbons with no benzene ring; include alkanes, alkenes, and alkynes.

Aromatic hydrocarbon

Hydrocarbons containing a conjugated ring, typically with a benzene ring.

Alkane

An aliphatic hydrocarbon with only C–C single bonds and no functional groups.

Alkene

An aliphatic hydrocarbon containing at least one C=C double bond.

Alkyne

An aliphatic hydrocarbon containing at least one C≡C triple bond.

Benzene

The simplest aromatic hydrocarbon; a six-membered ring with a conjugated system.

Primary carbon

A carbon atom bonded to exactly one other carbon atom.

Secondary carbon

A carbon atom bonded to two other carbon atoms.

Tertiary carbon

A carbon atom bonded to three other carbon atoms.

Quaternary carbon

A carbon atom bonded to four other carbon atoms.

Primary hydrogen

A hydrogen attached to a carbon that is bonded to one other carbon.

Secondary hydrogen

A hydrogen attached to a carbon that is bonded to two other carbons.

Tertiary hydrogen

A hydrogen attached to a carbon that is bonded to three other carbons.

Heteroatom

An atom other than carbon or hydrogen (e.g., oxygen, nitrogen, sulfur, halogens) in a molecule.

Lone pair

A nonbonding pair of electrons on a heteroatom that can influence reactivity.

Pi bond

A bond formed by sideways overlap of p orbitals; common in C=C and C=O.

Hydroxyl group (-OH)

A functional group that imparts polarity; in alcohols, contributes to water solubility.

Aldehyde

A carbonyl compound with the carbonyl carbon at the end of a carbon chain (R-CHO).

Ketone

A carbonyl compound with the carbonyl carbon within the carbon skeleton (R-CO-R').

Carboxylic acid

A carbonyl group with a hydroxyl group (R-COOH).

Amide

A carbonyl compound bonded to nitrogen (R-CONH2).

Carbonyl group

The C=O functional group; the carbon is electrophilic; oxygen has lone pairs and the group contains a pi bond.

C–Z bond

A bond between carbon and a heteroatom Z (e.g., C–O, C–N); often polar.

Alkyl halide

R-X where X is a halogen (F, Cl, Br, I).

Alcohol

R–OH; a hydroxy-containing compound; can be primary, secondary, etc.; may form ethers (R–O–R).

Ether

R–O–R; an oxygen atom single-bonded to two carbon-containing groups.

Amine

Organic compound containing nitrogen (RNH2, R2NH, or R3N).

Thiol

R–SH; sulfur analog of alcohol.

Sulfide (thioether)

R–S–R; sulfur atom bonded to two carbon groups.

Alkyl group

A hydrocarbon group attached to a molecule (represented as R); not itself a functional group.

Primary alcohol

An alcohol where the carbon bearing –OH is attached to one other carbon.

Secondary alcohol

An alcohol where the carbon bearing –OH is attached to two other carbons.

Primary alkyl chloride

An alkyl halide where the carbon bearing the halogen is attached to one other carbon.

Secondary alkyl chloride

An alkyl halide where the carbon bearing the halogen is attached to two other carbons.

Polarity

Distribution of electrical charge within a molecule; affects intermolecular forces.

Intermolecular forces

Forces that act between molecules; include van der Waals (London dispersion), dipole-dipole, and hydrogen bonding.

London dispersion forces

Weak intermolecular forces due to momentary dipoles from electron distribution; stronger with larger surface area.

Dipole-dipole interaction

Attractive forces between permanent dipoles of polar molecules.

Hydrogen bond

A strong type of dipole-dipole interaction where H is bonded to O, N, or F and interacts with a lone pair on another electronegative atom.

Polarizability

Ease with which the electron cloud around an atom is distorted by an electric field; larger atoms are more polarizable.

Boiling point

Temperature at which a liquid becomes a gas; higher when intermolecular forces are stronger.

Surface area effect on London forces

Larger surface area increases London dispersion forces and boiling point; branching reduces surface area and lowers these forces.

Intermolecular forces and biology

Hydrogen bonds contribute to protein folding and DNA double-helix stability.

Ion–ion interactions

Strong electrostatic forces between oppositely charged ions in ionic compounds; stronger than forces between covalent molecules.

Hydrogen bonding donor/acceptor requirement

A hydrogen bond involves a donor H attached to a electronegative atom (O, N, F) and an acceptor with a lone pair.

Functional group as determinant of properties

The presence and type of functional group largely determine bonding, shape, intermolecular forces, and reactivity.