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 9.6 kJ/mol (2.3 kcal/mol) more stable than the anti conformation. Draw Newman projections of these conformers, and explain this curious result.

Convert each Newman projection to the equivalent line–angle formula, and assign the IUPAC name.

(c)

(d)

Using Newman projections, draw the most stable conformer for each of the following:

c. 3,3-dimethylhexane, viewed along the C-3---C-4 bond

For the following molecule, draw the Newman projection (around the 2,3-bond) with a dihedral angle of 180° between the bromine and hydrogen.

Draw the conformer that is present in greatest concentration.

Looking down the indicated bond, show the three most stable conformations and choose the one that is most stable. Be sure that the first Newman projection you show is the one you see initially (before rotation). [Why should none of your three Newman projections show eclipsed conformations?]

(e) <IMAGE>

Which Newman projection best represents the most stable conformation of $C_2{H}_6$ (ethane) when viewed down the carbon-carbon bond?

Which of the following Newman projections best represents the most stable conformation of $C_2{H}_6$ (ethane) when viewed down the $C-C$ bond?