Organic Compounds: Nomenclature, Properties & Conformations

A comprehensive set of vocabulary flashcards summarizing major terms, structures, and physical-property concepts from the Chapter 3 lecture on organic compounds.

Alkane

A saturated hydrocarbon that contains only single C–C and C–H bonds and obeys the general formula CnH2n+2.

Straight-chain alkane

An alkane whose carbon atoms form one continuous, unbranched chain.

Constitutional isomer

Compounds that share a molecular formula but differ in the way their atoms are connected.

Systematic (IUPAC) nomenclature

Rule-based method of naming organic compounds so the name reflects the molecule’s structure.

Alkyl substituent

A group obtained by removing one hydrogen from an alkane; its name ends in “-yl.”

Alkyl group naming rule

Replace the “-ane” ending of the parent alkane with “-yl.”

Alkyl halide

An organic compound in which a halogen has replaced a hydrogen of an alkane.

Alcohol

A compound in which an OH group replaces a hydrogen of an alkane.

Amine

A compound derived from ammonia in which one, two, or three hydrogens are replaced by alkyl groups.

Ether

A compound in which an oxygen is bonded to two alkyl groups (R–O–R′).

Primary carbon (1°)

A carbon atom bonded to only one other carbon.

Secondary carbon (2°)

A carbon atom bonded to two other carbons.

Tertiary carbon (3°)

A carbon atom bonded to three other carbons.

Primary hydrogen

A hydrogen attached to a primary carbon.

“n-” prefix

Indicates a normal (unbranched) chain in some common names, e.g., n-butane.

“iso-” prefix

Indicates a chain that ends with two methyl groups attached to the next-to-last carbon.

Propyl group

CH3-CH2-CH2- ; obtained by removing a hydrogen from a terminal carbon of propane.

Isopropyl group

(CH3)2CH- ; obtained by removing a hydrogen from the secondary carbon of propane.

Butyl group

Any C4H9- substituent; four structural versions exist (n-, sec-, iso-, tert-).

sec-butyl group

CH3-CH2-CH(CH3)- ; a butyl group attached through a secondary carbon.

tert-butyl group

(CH3)3C- ; a butyl group attached through a tertiary carbon.

Octane number

A measure of a fuel’s resistance to engine knocking, defined relative to heptane (0) and 2,2,4-trimethylpentane (100).

Primary alkyl halide

An alkyl halide in which the halogen is bonded to a primary carbon.

Secondary alkyl halide

An alkyl halide in which the halogen is bonded to a secondary carbon.

Tertiary alkyl halide

An alkyl halide in which the halogen is bonded to a tertiary carbon.

Primary alcohol

An alcohol whose OH group is on a primary carbon.

Secondary alcohol

An alcohol whose OH group is on a secondary carbon.

Tertiary alcohol

An alcohol whose OH group is on a tertiary carbon.

Primary amine

An amine with one alkyl group attached to nitrogen (RNH2).

Secondary amine

An amine with two alkyl groups attached to nitrogen (R2NH).

Tertiary amine

An amine with three alkyl groups attached to nitrogen (R3N).

van der Waals forces

Weak induced dipole-induced dipole attractions present between all molecules; increase with surface area.

Dipole–dipole interaction

Attractive force between permanent polar molecules; stronger than van der Waals forces.

Hydrogen bond

A strong dipole–dipole interaction between H attached to O, N, or F and a lone pair on O, N, or F of another molecule.

Surface area effect

Greater molecular surface area leads to stronger van der Waals forces and higher boiling points.

Branching effect

Increased branching lowers surface area, reducing boiling point of alkanes.

Polarizable atom

An atom whose electron cloud is easily distorted; larger halogens are more polarizable.

Induced dipole–induced dipole

Another term for van der Waals (London) dispersion forces.

2,2,4-Trimethylpentane

Highly branched alkane assigned an octane number of 100.

Heptane

Straight-chain C7H16 given an octane number of 0.

Conformation

Any 3-D arrangement of atoms resulting from rotation about single bonds.

Staggered conformation

A conformation in which bonds on adjacent atoms are as far apart as possible; lowest torsional energy.

Eclipsed conformation

A conformation where bonds on adjacent atoms overlap when viewed along the bond axis; highest torsional energy.

Torsional strain

Energy increase caused by eclipsing bonds during rotation about a single bond.

Newman projection

End-on drawing that shows spatial relationships of bonds around a single bond.

Gauche conformation

A staggered arrangement where two bulky groups are 60° apart; higher in energy than anti.

Anti conformation

A staggered arrangement where the largest groups are 180° apart; lowest energy in butane.

Conformational analysis

Study of energy changes associated with different conformations of a molecule.

Potential-energy diagram

Graph of molecular energy versus torsional angle used to visualize rotational barriers.

Cycloalkane

A saturated hydrocarbon containing carbons joined in a ring.

Angle strain

Strain caused when bond angles deviate from the ideal 109.5° for sp3 carbons.

Chair conformation

Lowest-energy, strain-free 3-D shape of cyclohexane.

Axial position

A substituent orientation in cyclohexane that points perpendicular (up or down) to the ring plane.

Equatorial position

A substituent orientation in cyclohexane that lies roughly along the ring’s equator, away from the ring.

Ring flip

Interconversion of two chair conformations in cyclohexane; axial groups become equatorial and vice versa.

1,3-diaxial interaction

Steric repulsion between an axial substituent and axial hydrogens (or groups) on the same side of the ring two carbons away.

cis isomer (cycloalkane)

Two substituents located on the same side of a ring plane.

trans isomer (cycloalkane)

Two substituents located on opposite sides of a ring plane.

Solvation

Attractive interaction between solvent molecules and solute particles that stabilizes the solution.

Like dissolves like

Rule stating polar solutes dissolve in polar solvents and non-polar solutes in non-polar solvents.

Lipid bilayer

Double layer of phospholipids forming cell membranes, with polar heads outward and non-polar tails inward.

Amylose vs. cellulose difference

Starch (amylose) and cellulose differ by an equatorial vs. axial glycosidic bond, giving very different properties.

Tetrahedral bond angle

Ideal 109.5° angle between bonds from an sp3-hybridized carbon.