Conformation Stability of Ethane-1,2-Diol

[EnricoHendro]

Homework Statement

Conformational studies on ethane-1,2-diol (HOCH2-CH2OH) have shown the most stable conformation about the central C-C bond to be the gauche conformation, which is 9.6kJ/mol more stable than the anti conformation. Explain the curious result.

Relevant Equations

No equations

Hello there,
My attempted explanation/solution is :
“Torsional strain is caused by the tendency of the electron clouds in the interacting groups to repel each other, making it relatively difficult to rotate a group towards and through another group, as the repulsive force provides resistance to the rotation. However, in alcohol groups, we have H-O bond. This means that the alcohol groups in ethane-1,2-diol can form hydrogen bonds with each other, and therefore “pulling” one another towards each other (since intermolecular force is an attractive force). This hydrogen bond is stronger when ethane-1,2-diol is in gauche conformation, since both OH groups are closer than in anti. In a sense, it is easier to rotate the compound in gauche conformation due to the help from the Hydrogen Bond. This explains why gauche conformation of Ethane-1,2-diol is more stable than anti conformation.”

Is my attempted explanation correct?

 

[TeethWhitener]

Sounds fine. More concise would simply be that the hydrogen bonding overcomes the steric repulsion in the gauche configuration.