INTOCHEMISTRY / CONFORMATION LESSON
Newman Projections & Dihedral Angles
Recognize eclipsed, staggered, gauche and anti relationships.
Interpret Newman projections and connect torsional geometry to elimination.
1Choose the viewing bond
Look directly down a selected C–C sigma bond. The front carbon is the central point and the back carbon is represented by a circle.
2Recognize relative angles
Eclipsed relationships have a 0° dihedral; staggered relationships occur at 60° increments; a selected pair is gauche at ±60° and anti at 180°.
3Distinguish conformation and configuration
Rotation about an acyclic C–C bond alters conformation without breaking bonds or changing R/S configuration. Ring geometry can limit available orientations.
4Worked example
An anti Br–Cα–Cβ–H dihedral (180°) can align the reacting C–Br and neighboring C–H sigma bonds for an E2 transition state. A 60° relationship is not that anti arrangement.
Check your reasoning
Is every staggered conformer anti for the bond pair of interest?
Reveal the explanation
No. A staggered arrangement can be gauche (60°) or anti (180°) for a selected pair.