Question

Consider a cyclohexane with a methyl group at C1 position and a propyl group at C3 and C5 position and each of the first bond bonded to the cyclohexane in alkyl groups has wedge bond. I do not think this can be called a meso compound as the second and third bond of the propyls rotate freely and thus there is no plane of symmetry and it is chiral. Despite of that, some sources tend to regard those two propyls as a single unit that is called asPrand hence the compound is meso. Giving those second and third bond of the propyls with mixed wedge-wedge, wedge-dash, dash-wedge, and dash-dash also give same chemical name as (1r,3R,5S)-1-methyl-3,5-dipropylcyclohexane. I am wondering if those variants will be chiral or not. Whether those variants are chiral or not, I am also interested in how much is the optical activity of each variant.

Answer 1

A compound with a methyl group at C1 and propyl groups at C3 and C5 of cyclohexane may or may not be meso depending on the arrangement of substituents. The chirality and optical activity depend on the presence or absence of a plane of symmetry, which can vary with different substituent orientations.

Step-by-step explanation:

The question concerns a hypothetical cyclohexane derivative with a methyl group at the C1 position and a propyl group at both the C3 and C5 positions. It questions whether differing the position of wedge and dash bonds in the propyl groups affects the chirality of the molecule, and if such a molecule would be optically active.

According to the definition of meso compounds, a molecule must have an internal plane of symmetry and be optically inactive. However, variations in the propyl group attachments (wedge-wedge, wedge-dash, dash-wedge, dash-dash) could potentially alter the compound's symmetry and chirality.

When dealing with alkyl substituents on cycloalkanes, IUPAC nomenclature rules dictate how these are named. The substituents are listed in alphabetical order, and the ring carbon attached to the first listed substituent is numbered as 1. The numbering continues in a direction that gives the lowest numbers to subsequent substituents.

Concerning meso compounds, these exhibit at least two stereocenters and have a plane of symmetry, making them achiral and optically inactive. However, this compound's stereochemistry must be analyzed for each specific variant to determine the presence of a plane of symmetry and its chirality.