Newman projections: ethane template

Staggered and eclipsed ethane as Newman projections, with the dihedral angle and the threefold torsional energy curve (barrier about 12 kJ mol⁻¹).

What the template shows

• Look straight down the C–C bond: front carbon = centre point, back carbon = circle
• Conformations of ethane
• dihedral 60°, lowest energy
• dihedral 0°, highest energy (drawn slightly offset)
• H–C–C–H dihedral angle
• Energy / kJ mol⁻¹
• Conformations interconvert by rotation about a single bond; they are not isomers you can isolate at room temperature.
• Staggered (60°) is the energy minimum; eclipsed (0°) is the maximum, about 12 kJ mol⁻¹ higher (torsional strain, roughly 4 kJ mol⁻¹ per eclipsed H/H pair).
• The barrier is small compared with thermal energy at 25 °C, so ethane rotates about 10¹¹ times a second.
• The dihedral (torsion) angle is the angle between two bonds on the front and back carbons, seen down the C–C bond.
• Wedge = toward you, hash = away from you · every part of this figure is editable

Drawn with 8 atoms, 447 shapes – every one editable in MolDraw.

Sources

• Clayden, Greeves & Warren, Organic Chemistry, 2nd ed., OUP 2012, ch. 16 Textbook
• Eliel & Wilen, Stereochemistry of Organic Compounds, Wiley 1994, ch. 10 Textbook