is more stable by 0.21 kcal/mol (880 J/mol). A gauche effect has also been reported for a molecule featuring an all-syn array of four consecutive fluoro substituents. The reaction to install the fourth one is stereoselective: The gauche effect is also seen in 1,2-dimethoxyethane and some vicinal-dinitroalkyl compounds. The alkene cis effect is an analogous atypical stabilizing of certain alkenes. External influences 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. Another case is trans-1,2 difluorocyclohexane, which has a larger preference for the di-equatorial conformer, rather than the anti-diaxial conformer, in more polar solvents. See also Anomeric effect References Stereochemistry