Final answer:
To classify two disubstituted cyclohexane molecules, we compare their three-dimensional structures to determine if they are enantiomers, diastereomers, or another type of isomer.
Step-by-step explanation:
To classify the pair of two disubstituted cyclohexane molecules as the same compound, enantiomers, diastereomers, constitutional isomers, or not isomeric, we need to consider their structures and how they relate to each other in three-dimensional space.
A molecule can have more than one stereocenter, an example being 1,2-dimethylcyclopropane with two asymmetric carbons. Such molecules can exist as stereoisomers, which are classified as either enantiomers or diastereomers. Enantiomers are non-superimposable mirror images, while diastereomers are stereoisomers that are not mirror images. Molecules that differ at all stereocenters are enantiomers, while those that differ at one or more (but not all) stereocenters are diastereomers.
Cis-trans isomers, a type of diastereomer, require a molecule to have a double bond, which restricts rotation and allows for the possibility of different spatial arrangements of the substituents.
For enantiomers to exist, a molecule must have at least four different atoms or groups connected to a central asymmetric carbon. If there is a plane of symmetry, as in the case of certain meso compounds, the molecule is not chiral and does not have enantiomers.
In summary, depending on the relative positions of the substituents on the cyclohexane, the two molecules can be identified as any of the aforementioned classifications based on the relationship of the substituents to each other and the overall symmetry of the molecules.