Staggered
From Biocrawler, the free encyclopedia.
In chemistry a staggered conformation is a chemical conformation that exists in any open chain single chemical bond connecting two sp3 hybridised atoms as a conformational energy minimum.
staggered conformation left, eclipsed conformation right
In the example of ethane in newman projection a hydrogen atom on one carbon atom has a 60° angle with respect to the nearest hydrogen atom on the other carbon so that steric hindrance is minimised. The staggered conformation is more stable by 12.5 kJ/mole than the eclipsed conformation which is the energy maximum for ethane.
In butane two additional staggered conformations exist the anti conformation (left) and the gauche conformation (right).
Both conformations are free of torsional strain but in the gauche conformation the two methyl groups are in closer proximity than the sum their van der Waals radii. The interaction between the two methyl groups is repulsive (van der Waals strain) and a energy barrier results. In n-pentane the terminal methyl groups experience additional pentane interference.
