Isomer — Definition, Formula, Properties & Uses | AllChemicals | AllChemicals

Also Known As	Structural isomer, stereoisomer, constitutional isomer, geometrical isomer

What is Isomer?

One of two or more compounds with the same molecular formula but different arrangements of atoms. Structural isomers have different connectivity; stereoisomers (geometric and optical isomers) have the same connectivity but different spatial arrangements. Isomers can have very different properties.

Properties & Characteristics

Isomer refers to one of two or more compounds with the same molecular formula but different structural arrangements (structural isomers) or spatial arrangements (stereoisomers). Structural isomers differ in connectivity (chain isomers, position isomers, functional group isomers). Stereoisomers have the same connectivity but differ in 3D arrangement (geometric/cis-trans isomers, optical/enantiomers, conformational isomers). The number of possible isomers increases rapidly with molecular size.

Uses & Applications

Isomerism is critically important in drug development (enantiomers may differ in activity and toxicity), in petroleum chemistry (branched alkane isomers have higher octane ratings), in biochemistry (enzyme substrate specificity often distinguishes isomers), and in materials science (different polymer tacticity isomers have different properties — isotactic vs. atactic polypropylene).

Safety Information

Isomers can have dramatically different properties and hazards. Diethyl ether (a solvent) and 1,3-dioxolane are isomers with different boiling points, flammabilities, and toxicities. Pharmaceutical isomer control (enantiomeric purity) is a strict regulatory requirement to prevent administering potentially harmful non-active isomers.

Always consult the SDS/MSDS before handling any chemical. This information is for educational purposes only.

Key Facts

Term Isomer

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Synonyms Structural isomer, stereoisomer, constitutional isomer, geometrical isomer

Frequently Asked Questions

What is Isomer?

One of two or more compounds with the same molecular formula but different arrangements of atoms. Structural isomers have different connectivity; stereoisomers (geometric and optical isomers) have the same connectivity but different spatial arrangements. Isomers can have very different properties.

What is Isomer used for?

Is Isomer hazardous?

More "I" Terms

Ideal Gas Ideal Gas Law PV = nRT | R = 8.314 J/(mol·K) Ideal Solution Ideal solution: Raoult's law holds; ΔH_mix = 0, ΔV_mix = 0 Ideal Solution Indicator Visual pH/endpoint indicator; e.g., phenolphthalein: colourless (acid) → pink (base) Indicators Indium In Induced Dipole Induced dipole: α × E (α = polarisability; E = electric field) Inert Gas Inert S Pair Effect Infrared Spectroscopy IR: 4000–400 cm⁻¹; C=O at ~1720 cm⁻¹ Inhibition Ki = [I]×Km / ([S](Vm/v − 1))

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