Chapter 3 Structure and Properties Alkanes

stereoisomers produced by rotation (twisting) about σ bonds, and are often rapidly interconverting at room temperature

conformational isomer

CH3CH2Ch2OH CH3Ch2OCH3 CH3CH2CH3

Arrange the organic compounds from most soluble in water to least soluble in water.

2-methylhexane

Choose the molecule that has the higher boiling point. 2-methylhexane or 2,3-dimethylpentane

cyclohexane

Choose the molecule that has the higher boiling point. Hexane or Cyclohexane

2 3 180

How many gauche interactions are in the Newman projection at 180°? How many gauche interactions are in the Newman projection at 300°? Which is the most stable staggered conformation?

2,3‑dimethylbutane

IUPAC Name

The staggered Newman projection is most stable. The less gauche interactions, the more stable the Newman projection.

Identify the relative stability of each Newman projection.

Cyclopentane

Name

staggered, 3 gauche

Projection and gauche interactions

2‑methylpentane and 3‑methylpentane 2,3‑dimethylbutane and 2‑methylpentane

Which pairs of molecules are structural isomers? 2‑methylpentane and 3‑methylpentane hexane and 2‑methylhexane 2,3‑dimethylbutane and 2‑methylpentane 2‑methylpentane and 2‑methylhexane