Search results
Results From The WOW.Com Content Network
The study of the energetics of bond rotation is referred to as conformational analysis. [6] In some cases, conformational analysis can be used to predict and explain product selectivity, mechanisms, and rates of reactions. [7] Conformational analysis also plays an important role in rational, structure-based drug design.
Butane molecule represented on a staggered and eclipsed Newman projection down a carbon-carbon bond Butane molecule and all of its possible Newman conformations represented on a relative energy diagram. The diagram takes staggered and eclipsed conformations, as well as gauche and anti interactions into account.
The example below is looking down the C2 and C3 bond. Below is the sawhorse and Newman representation of butane in an eclipsed conformation with the two CH 3 groups (C1 and C4) at a 0-degree angle from one another (left). If the front is rotated 60° clockwise, the butane molecule is now in a staggered conformation (right).
This isn't always the case; if the difference in enthalpy is small, entropy can have a larger effect on the equilibrium. For example, n-butane has two possible conformations, anti and gauche. The anti conformation is more stable by 0.9 kcal mol −1. [1] We would expect that butane is roughly 82% anti and 18% gauche at room temperature.
English: Newman projections of butane conformations & their relative energy differences (not total energies). Conformations form when butane rotates about one of its single covalent bond. Torsional/dihedral angle is shown on x-axis. Conformations (according to IUPAC): A: antiperiplanar, anti or trans B: synclinal or gauche C: anticlinal or eclipsed
In 1978, together with M. R. Peterson, he carried out the first ab initio calculations and prepared a potential energy hyperplane for solving the n-butane conformational problems. [ 10 ]
The gauche effect is very sensitive to solvent effects, due to the large difference in polarity between the two conformers.For example, 2,3-dinitro-2,3-dimethylbutane, which in the solid state exists only in the gauche conformation, prefers the gauche conformer in benzene solution by a ratio of 79:21, but in carbon tetrachloride, it prefers the anti conformer by a ratio of 58:42. [9]
Conformational analysis of odd-membered rings suggests they tend to reside in less symmetrical forms with smaller energy differences between stable conformations. [ 9 ] Chelating macrocyclic structures of interest in inorganic and supramolecular chemistry, an example array.