Octadecanedioic Acid (CAS 871-70-5): Uses, Properties & Applications

2026.08.20

Octadecanedioic Acid (CAS 871-70-5): Properties, Uses and Applications of a C18 Dicarboxylic Acid

Octadecanedioic Acid, CAS 871-70-5, is a long-chain α,ω-dicarboxylic acid with an 18-carbon molecular framework and a carboxylic acid group at each end.

It is also known as 1,18-octadecanedioic acid and has the molecular formula C₁₈H₃₄O₄ with a molecular weight of approximately 314.46 g/mol. PubChem classifies it as an α,ω-dicarboxylic acid derived from an octadecane carbon skeleton.

What makes Octadecanedioic Acid particularly useful is the combination of two different structural features:

• two reactive terminal carboxyl groups;

• a relatively long C18 aliphatic segment.

Together, these features allow the molecule to function as a building block in polymer chemistry, functional intermediate development and selected peptide-related research.

Key Chemical Information

The identity, formula and molecular weight are consistently reported by PubChem, NIST and commercial reference suppliers.

Why Does the C18 Structure Matter?

Understanding Octadecanedioic Acid uses starts with understanding its molecular structure.

Two Terminal Carboxyl Groups

A carboxyl group is present at each end of the molecule.

This bifunctional structure allows Octadecanedioic Acid to participate in transformations commonly associated with carboxylic acids, including ester- and amide-forming chemistry.

As a result, the molecule can serve as a structural building block rather than simply as a terminal reagent.

Long Aliphatic Chain

Between the two carboxyl groups is a long hydrocarbon segment.

Compared with shorter-chain dicarboxylic acids, this creates a larger non-polar region and greater spacing between the two terminal functional groups.

In molecular and polymer design, chain length can influence characteristics such as molecular spacing, hydrophobic character and flexibility. The practical effect, however, depends on the complete molecular or polymer system and should be evaluated experimentally.

Major Octadecanedioic Acid Applications

Polyamide Chemistry

One of the best-documented applications of Octadecanedioic Acid is in polyamide research.

Published work has investigated polyamides containing Octadecanedioic Acid, including nylon-2,18, nylon-3,18, nylon-4,18, nylon-6,18 and related structures. A separate study examined nylon 6/6,18 copolyamides and reported increased resistance to organic solvents as the proportion of nylon 6,18 increased.

This makes octadecanedioic acid polyamide an important technical application area rather than simply a supplier marketing claim.

Polyester and Ester-Based Structures

Because Octadecanedioic Acid contains two carboxyl groups, it can also participate in ester-forming chemistry with suitable alcohol-containing components.

This makes it relevant to research involving:

• long-chain polyester structures;

• polyester polyol design;

• specialty ester derivatives;

• functional long-chain materials.

The exact properties of the resulting material depend on the complete monomer system, molecular weight and processing conditions.

Functional Organic Intermediates

Octadecanedioic Acid can also serve as a starting material for developing long-chain derivatives.

Researchers may modify one or both terminal carboxyl groups to create:

• mono-protected derivatives;

• ester derivatives;

• amide derivatives;

• asymmetric functionalized intermediates;

• linker-related structures.

This makes the compound relevant to multistep organic synthesis where the C18 spacer itself is an important part of the target structure.

Peptide-Related Side-Chain Research

Octadecanedioic Acid also appears in peptide-related chemistry.

The Japanese Accepted Names database for Semaglutide states that its peptide structure contains a Lys residue attached to 1,18-octadecanedioic acid through a linker containing one Glu and two 8-amino-3,6-dioxaoctanoic acid units.

This gives Octadecanedioic Acid a distinct role as a C18 diacid structural unit in certain peptide side-chain research.

It should, however, be understood as one component within a larger linker architecture rather than as the complete side chain.

What Should R&D Teams Evaluate?

For a technical project, knowing the CAS number is only the first step.

Important evaluation factors include:

Identity

Confirm:

• Octadecanedioic Acid

• CAS 871-70-5

• C₁₈H₃₄O₄

• molecular weight approximately 314.46

Purity

Purity requirements should match the downstream research or manufacturing process.

A general catalog specification should not replace review of the actual batch data.

Analytical Documentation

Relevant batch documentation may include:

• Certificate of Analysis;

• specification;

• identity information;

• purity data;

• additional analytical information required by the project.

Commercial reference suppliers such as TCI provide specifications, COA and analytical-document access for Octadecanedioic Acid, illustrating the type of documentation technical buyers commonly review.

Frequently Asked Questions

What is Octadecanedioic Acid?

Octadecanedioic Acid is a C18 long-chain α,ω-dicarboxylic acid containing carboxyl groups at both ends of the molecule. Its CAS number is 871-70-5.

Is 1,18-Octadecanedioic Acid the same compound?

Yes. 1,18-Octadecanedioic Acid is a commonly used alternative name for CAS 871-70-5. NIST lists this name among the synonyms for the compound.

What is Octadecanedioic Acid used for?

Major research areas include polyamide chemistry, polyester and ester-based structures, long-chain functional intermediate development and selected peptide side-chain research.

Why is chain length important?

The C18 chain creates a long aliphatic spacer between two reactive carboxyl groups. This distinguishes Octadecanedioic Acid structurally from shorter-chain dicarboxylic acids and can influence the design of downstream molecules and polymers.

Octadecanedioic Acid for R&D and Manufacturing Projects

For project evaluation, Octadecanedioic Acid should be assessed based on identity, purity, batch data, documentation and downstream application requirements.

Shandong Juntai Pharmaceutical can support discussions around product specifications, COA requirements and project-related technical information.

For research and manufacturing use only.