[Schrödinger]

Please see the attached picture. I found certain discrepancies in the values; they didn't add up to the values of the energies tabulated. If anyone has time, please use the values for k₀, k₁...k₄ given in the tables, and using the equation, please calculate the energies and see for yourself that they don't match. Moreover, they just don't seem to make any sense. For example, the table says that the energy is greatest when the dihedral angle is 180 degrees. Is there something I'm missing (like the definition of θ)? Or is this a mistake in the text?

Book : Computational Chemistry : Introduction to the theory and applications of Molecular and Quantum Mechanics
Author : Errol Lewars
Page : 52

For those of you who arent able to see the uploaded picture, please use :

[Tinus]

I obtained these results when using the equation you've shown:

Angle - E(calc)
0 - 0,18
30 - 6,7
60 - 14
90 - 8,8
120 - 3,5
150 - 15
180 - 25

so apart from the 0 degrees they match . A bit inconsistent in rounding their values though.

[Schrödinger]

Yeah alright. Their numbers seem to agree with the formula (my bad), but still this is kind of confusing.

The θ values given refer to the dihedral angles right? In that case, let's take butane. Isnt 180° between the methyl groups in C-2 and C-3 a more preferred conformation (anti) when compared to all the others (gauche, eclipsing, etc)? Why is it that the energy of the conformation with 180° dihedral angle the greatest (25 kJmol^-1)?