135isomer

The 135isomer, or 1,3,5-isomer, is a term used in organic chemistry to describe a class of compounds in which three substituents occupy the positions 1, 3, and 5 on a six-membered ring, most commonly a benzene ring. This substitution pattern is a subset of tri-substituted aromatics and is often discussed in the context of 1,3,5-trisubstituted benzene derivatives.

In nomenclature, 1,3,5-substitution is equivalent to a meta-type arrangement among the substituents, with the ring’s symmetry depending on whether the substituents are identical or different. When the three substituents are identical, the molecule exhibits higher symmetry (often D3h) and may show a single environment for certain nuclei in spectroscopic analysis. When the substituents differ, the symmetry is reduced and the pattern becomes more complex.

Common examples include 1,3,5-trinitrobenzene and 1,3,5-trichlorobenzene. These compounds illustrate how the 1,3,5 pattern can occur with different functional groups and how this pattern influences physical properties, reactivity, and applications.

Synthesis of 135isomers typically involves strategies that enable selective tri-substitution of a benzene ring, such as sequential electrophilic aromatic substitutions, directed substitutions, or cross-coupling approaches starting from prefunctionalized cores. The choice of substituents and sequence controls regioselectivity and yields.

Analytical methods for identifying 1,3,5-substitution rely on NMR, infrared spectroscopy, mass spectrometry, and, when possible, X-ray crystallography to confirm substitution pattern and symmetry.

See also: ortho-, meta-, and para-substitution; tri-substituted aromatics; 1,3,5-trisubstituted benzene derivatives.