Orgo I Chapter 4: Organic Compounds: Cycloalkanes and Their Stereochemistry

cycloalkanes (alicyclic compounds)

saturated cyclic hydrocarbons

general formula of cycloalkanes

(CH2)n

True or False: cycloalkanes are more flexible than open chain alkanes

False, open chain alkanes have relatively free rotation around single bonds, while cycloalkanes are more fixed to their plane

True or False: the larger cycloalkanes the more rotational freedom

True

cis cyclo isomer

same face of the ring, both out of or into the page

trans cyclo isomer

opposite faces of the ring, one is out of the page and one in

stereoisomer

atoms connected in the same order but differing in three-dimensional orientation

If two substituents are both out of or both into the page are they cis or trans

cis

angle-strain

strain induced in a molecule when bond angles are forced to deviate from the ideal 109 tetrahedral value

torsional strain

strain due to eclipsing of bonds between neighboring atoms

steric strain

the strain due to repulsive interactions when atoms approach each other too closely

what are the property results of cyclopropane's bent bonds

cyclopropane bonds are weaker and more reactive

chair conformation

strain free 3-D shape for cyclohexanes

boat conformation

no angle strain lots of eclipsing interactions

twist-boat conformation

nearly free of angle strain but has both steric and torsional strain

are monosubstituted cyclohexanes generally more stable in the axial or equatorial position

equatorial

1,3-diaxial interaction

the strong steric strain between two axial groups on cyclohexane carbons with one carbon between them

how much energy for H-H eclipsed interaction?

4.0 kJ/mol

how much energy for CH3-H eclipsed interaction?

6.0 kJ/mol

how much energy for CH3-CH3 gauche interaction?

3.8 kJ/mol

how much energy for CH3-CH3 eclipsed interaction?

11.0 kJ/mol