Newman Projections
Views along a C-C bond showing staggered and eclipsed conformations.
Views along a C-C bond showing staggered and eclipsed conformations.
A Newman projection views a molecule down a single carbon-carbon bond, with the front carbon shown as a point and the rear carbon as a circle. The three bonds from each carbon are drawn as lines radiating from the centre, which makes it easy to see the angle between groups on adjacent carbons. A staggered conformation places front and rear bonds 60 degrees apart and has lower energy than an eclipsed conformation, where they line up. In butane, the anti staggered arrangement is the most stable because the two largest groups are as far apart as possible.
Key ideas: View down one C-C bond: the front carbon is a point where three bonds meet, the back carbon is a circle. Staggered has 60 degree dihedral angles, eclipsed has 0. Plot energy versus dihedral angle from 0 to 360 degrees to get the profile. For butane, the three staggered forms are one anti at 180 degrees and two gauche at 60 and 300 degrees.
Common mistakes and connections: Common errors are drawing back-carbon groups aligned with the front when they should be offset, and misidentifying gauche versus anti. Students also forget that front and back carbons each carry three substituents. Links to conformations, cyclohexane chairs and E2 stereochemistry (anti-periplanar geometry).
Butane viewed along C2-C3: anti is lowest, gauche about 3.8 kJ/mol higher, and the fully eclipsed methyl-methyl form near 22 kJ/mol. The interactive lesson shows this as a live animation or chart.
In ethane, the eclipsed conformation lies about 12 kJ/mol above the staggered conformation.
Views along a C-C bond showing staggered and eclipsed conformations.
Newman Projections is a intermediate topic in Organic Chemistry. It builds on the vocabulary of beginner topics in this area.
Study these earlier topics in Organic Chemistry first: CIP Priority Rules, Fischer Projections, Conformations.
The next topics in Organic Chemistry are Cyclohexane Chair Conformation and Ring Strain.
Yes. The interactive lesson includes a self-check question on Newman Projections, and the Organic Chemistry quiz draws on every topic in this area.
Newman Projections is topic 28 of 148 in Organic Chemistry.