Chem 334 - Summer 1998 - Organic Chemistry I Dr. Carl C. Wamser

Chapter 4 - Cyclic Alkanes

structure and nomenclature

cis/trans stereoisomers

relative stabilities

heats of formation
heats of combustion

causes of small-ring strain:

1) bond-angle strain (poor orbital overlap)
2) eclipsing strain
3) gauche interactions
4) transannular strain

small cycloalkanes

cyclopropane - planar
cyclobutane - slightly puckered

reactions - relatively easy ring cleavage

cyclopentane - envelope or half-chair conformations

conformations of cyclohexane:

chair conformations
boat and twist-boat conformations
potential energy diagram

substituted cyclohexanes:

axial and equatorial substituent locations

PRACTICE DRAWING ACCURATE CHAIR FORMS WITH SUBSTITUENTS

relative stabilities of substituted cyclohexanes

equatorial generally preferred over axial

larger cycloalkanes

bicyclo and polycycloalkanes: nomenclature

natural products:

terpenes (plant products from isoprene - C5 units)
steroids (distinctive four-ring system)