Newman Bond projection

1. Use a Newman projection of the C3C4 bond of 2m4-dimethyl-3-phenyl-4-ethylhexane to show the most
stable conformation first. Rotate through all of the eclipsed and staggered conformations. Using the energy
values provided in the table below, calculate the relative energies of the different conformations. Plot the
changes in energy in the graph diagram provided. Calculate a ratio of least stable to most stable based on H
values. Hint: Draw a 2D structure first and “bold” the bond viewed in your Newman projection, then decide your
line of sight.
2D structure
Newman projections:
lowest PE
2,4-dimethyl-3-phenyl-4-ethylhexane
H) =
Keq = 10
0
1
2
3
4
5
6
most stable
least stable
H) =
7
8
G  H
Keq = 10
– H
2.3RT
H Me Et i-Pr t-Bu Ph Br
H 1.0 1.4 1.5 1.6 3.0 1.7 1.6
Me 1.4 2.5 2.7 3.0 8.5 3.3 2.8
Et 1.5 2.7 3.3 3.8 10.0 4.0 3.1
i-Pr 1.6 3.0 3.8 7.8 13.0 8.1 3.6
t-Bu 3.0 8.5 10.0 13.0 23.0 13.5 9.1
Ph 1.7 3.3 4.0 8.1 13.5 8.3 4.2
B

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