Additional Problems for practice: 1. Draw the two chair...
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Additional Problems for practice: 1. Draw the two chair conformations of cis and trans-1-chloro-2- methylcyclohexane. Cl Me Me Cl cis-1-chloro-2-methylcyclohexane Cl Me H H Me Cl H H trans-1-chloro-2-methylcyclohexane In each case, which is more stable? By how much (use table 3-6 in text) Cl Me Me Cl Cl Me H H Me Cl H H more stable 0.5 kcal/mol 1.7 kcal/mol ΔG=1.2 kcal/mol more stable diequatorial 0kcal/mol 1.7 kcal/mol + 2.2 kcal/mol ΔG=2.2 kcal/mol 0.5 kcal/mol Keq=0.13 ΔG = -RTlnKeq Keq=0.025 11.5% 88.5% 97.5% 2.5%
Transcript of Additional Problems for practice: 1. Draw the two chair...
Additional Problems for practice:
1. Draw the two chair conformations of cis and trans-1-chloro-2-methylcyclohexane.Cl
Me
Me
Cl
cis-1-chloro-2-methylcyclohexane
ClMe
H
H
Me
Cl
HH
trans-1-chloro-2-methylcyclohexane
In each case, which is more stable? By how much (use table 3-6 in text)
Cl
Me
Me
Cl
ClMe
H
H
Me
Cl
HH
more stable
0.5 kcal/mol
1.7 kcal/mol
ΔG=1.2 kcal/mol
more stablediequatorial0kcal/mol
1.7 kcal/mol +
2.2 kcal/mol
ΔG=2.2 kcal/mol
0.5 kcal/mol
Keq=0.13
ΔG = -RTlnKeq
Keq=0.025
11.5%88.5%
97.5% 2.5%
2. Which isomer is more stable, cis or trans decalin? Explain your answerin terms of the steric interactions of the two molecules.
H
H
trans-decalin (rigid)
H
H
cis-decalin H
H
cis-decalin
No 1,3 diaxial interactions
HH H
H
extensive 1,3-diaxial interactions
Thus, trans-decalin is more stable than cis-decalin
3. Draw the following disubstituted cyclohexanes and label thesubstituents as axial or equatorial. The substituents can be any alkylgroup of your choosing. Remember to include the ring-flip structure aswell.
(a) 1,3 trans disubstituted(b)1,3-cis disubstituted(c)1,5-cis disubstituted(d) 1,4-cis disubstituted(e) 1,5-trans disubstituted(f) 1,6-trans disubstituted
ax
axeq
eq
ax
eq
ax
eq
ax
eq
ax eq
ax
eqeq
ax
ax
eq
eq
ax
ax
eqax
eq
a
b
c
d
e
f
