# Alkanes and Cycloalkanes

## Vocabulary

### alkane

hydrocarbon containing only ${\rm C{-}C}$ single bonds and hydrogen with CnH2n+2 stoichiometry

### alkene

hydrocarbon containing at least one carbon-carbon double bond (${\rm {C{=}C}}$) with CnH2n stoichiometry

### alkyne

hydrocarbon that contains at least one carbon-carbon triple bond (${\rm {C{\equiv}C}}$) with CnH2n-2 stoichiometry

### angle strain

molecular instability resulting from carbon atoms bonded in alkanes at angles less than 109.5°

### anti-conformation

staggered conformation that exhibits no steric strain due to two groups on adjacent atoms having a dihedral angle of 180°

### axial

position in which a substituent is parallel to the axis of the ring

### bicyclic compound

molecule containing two rings

### boat conformation

less stable, nonplanar conformation seen in cyclohexane rings

### chair conformation

stable, nonplanar conformation seen in cyclohexane rings

### cis-trans isomerism

one of two or more molecules that have the same molecular formula and bond structure but differ in the positions of their substituents around a rigid part of the molecule

### conformational analysis

three-dimensional analysis of molecules to find the least-strained conformation or arrangement in three-dimensional space

### cyclic

describes a molecule containing a ring with at least three carbons

### dihedral angle

angle between two atoms on adjacent carbons in a Newman conformation

### eclipsed conformation

conformation of an alkane where the dihedral angle is 0°

### equatorial

position in which a substituent is perpendicular to the axis of the ring

### flip-chair conformation

conversion of one cyclohexane chair conformation to another by rotation around the carbon-carbon single bonds

### gauche conformation

staggered conformation that exhibits steric strain due to two groups on adjacent atoms having a dihedral angle of 60°

### locant

position or location of a substituent in an organic molecule

### Newman projection

projection that depicts the molecular conformation and is particularly useful for determining the best conformation of the molecule around a bond

### ring strain

combination of angle and torsional strain that determines a molecule's stability

### sawhorse projection

representation of a molecule from an angle that resembles a carpenter's sawhorse

### staggered conformation

conformation of an alkane where the dihedral angle is 60°

### steric strain

strain resulting from nonbonded atoms being forced close to each other

### substituent

atom or group of atoms (functional group) that replaces a ${\rm {C{-}H}}$ bond in an organic compound

### torsional strain

resistance to bond rotation due to electronic repulsion that results from nonbonded atoms being forced close to each other

### wedge-and-dash projection

way to represent molecular conformation with solid and dashed wedges to indicate the position of substituents