Maleate-salt preparation
Attributed industrial references identify maleic acid in preparing maleate salts of antihistamines and related drugs. [3]
01
THE ESSENTIALS
Maleic Acid in 30 Seconds
Two carboxyl groups lie on the same side of the carbon–carbon double bond. Fumaric acid places them on opposite sides. The same formula and molecular weight do not establish interchangeable identity.
Maleic acid is the Z/cis geometric isomer of butenedioic acid. It is distinct from fumaric acid, malic acid and maleic anhydride. [1] [3]
Safety at a glance — TCI and Merck classify these maleic-acid products as corrosive, harmful by ingestion or skin contact, capable of skin sensitization, and irritating to the respiratory tract. ICSC warns of irritating fumes including maleic anhydride on heating and of aquatic toxicity. Dust exposure and allergic skin reactions must not be minimized because maleate salts occur in medicines. [4] [5] [6] [14]
Condensed connectivity schematic; see the specified stereochemical identity below. [1]
02
GO A LITTLE DEEPER
Understanding Maleic Acid
THE SIMPLE EXPLANATION
The functional groups
Two carboxyl groups lie on the same side of the carbon–carbon double bond. Fumaric acid places them on opposite sides. The same formula and molecular weight do not establish interchangeable identity. [1]
A LITTLE DEEPER
What the structure changes
The cis arrangement permits intramolecular hydrogen bonding, while intermolecular associations and crystal packing also affect the properties. First and second acid ionization steps are separate equilibria; a statement that one isomer is simply stronger misses this distinction. [1] [12] [15]
Technical detail Identity, dissociation & specification
The neutral free-acid formula, connectivity and specified geometric identity are distinct from a salt, ester, polymer or anhydride. Numeric pKa is not promoted where retrieved conditions or conflicting measurements remain insufficiently resolved. [1] [2] [4] [5] [6]
Acid–base reference values describe equilibria under specified conditions. They are not a substitute for a validated formulation or an assay on the purchased lot.
03
MAKE THE CONNECTION
How Maleic Acid Compares
Similar names and functional groups do not mean interchangeable chemicals.
SIDE-BY-SIDE COMPARISON
Maleic Acid vs Fumaric Acid
Unsaturated aliphatic dicarboxylic acid
versusUnsaturated dicarboxylic acid
Fixed comparison for this prototype. Acid selectors are disabled; additional comparisons are coming later.
| Property | Maleic Acid | Fumaric Acid |
|---|---|---|
| Molecular formula | C₄H₄O₄ [1] | C₄H₄O₄ [7] |
| Molecular weight | 116.07 g/mol [1] | 116.07 g/mol [7] |
| Carbon atoms | 4 [1] | 4 [7] |
| Carboxyl groups | 2 [1] | 2 [7] |
| Structure | HOOC–CH=CH–COOH|Z / cis identity [1] | HOOC–CH=CH–COOH · E (trans) [7] |
| Chemical family | Unsaturated aliphatic dicarboxylic acid [1] | Unsaturated dicarboxylic acid [7] |
| Identity focus | Z / cis free acid [1] | Solid [7] |
Chemical identities are compared here; supplier grades, concentrations, and stereochemical specifications are separate purchasing attributes. pKa values retain their stated conditions; no quantitative solubility ranking is implied. The structure schematic does not encode stereochemistry.
When Might You Choose One Instead of the Other?
Choose maleic acid when a validated synthesis or salt-formation method specifies the cis acid. Choose fumaric acid when it specifies the trans acid. Confirm counterion identity and purity; neither a resin-intermediate context nor a familiar pharmaceutical maleate name qualifies a reagent for patient use. [1] [3] [7]
Specified starting material
Maleic Acid
Match HOOC–CH=CH–COOH|Z / cis identity and the method’s required chemical form.
Fumaric Acid
Match HOOC–CH=CH–COOH · E (trans); verify the identity before substituting a related acid.
Before choosing: match the reaction or formulation, then verify the exact form, grade, assay basis, and impurities. These contexts do not establish suitability for an industrial or regulated application.
04
FROM STRUCTURE TO APPLICATION
What Is Maleic Acid Used For?
Maleate-salt preparation
Attributed industrial references identify maleic acid in preparing maleate salts of antihistamines and related drugs. This is an intermediate role: the qualified drug salt is a separate substance, and the acid is not itself the therapeutic agent. [3]
Chemical and resin intermediates
Industrial references identify maleic acid as an intermediate for other acids and resin-related chemistry. The acid, its anhydride and the finished polymer remain separate identities; broad anhydride application lists are excluded. [3]
06
SOURCE WITH CONTEXT
Maleic Acid Suppliers
Compare specific products and package options. Listings are not ranked recommendations.
3 suppliers · 3 products · 5 package listingsLatest supplier check: October 3, 2026
Package sizes stay grouped under the supplier product. Assay methods, product forms, and regional markets remain visible. TCI M0006 specifies minimum 99% titration but minimum 98% GC. Merck 800380 specifies HPLC area and acidimetric assays separately. All displayed entries are free-acid solids; Wako’s discontinued 0.1 mol/L item is excluded.
Scroll horizontally if needed. Supplier and package identity stay visible.
| Supplier | Product / Grade | Purity / Assay | Package Size | Public Price | Normalized Price | Documentation | Last Checked | Action |
|---|---|---|---|---|---|---|---|---|
| TCI AmericaMaleic Acid | Named grade not statedM0006 · 25 gcis identity. The 99% titration headline is not the separate GC minimum. | GC: minimum 98.0% Neutralization titration: minimum 99.0% | 25 g | $23.00USD · US public price | Not comparedGrades, assay bases, or forms differ | Document notes: TCI America
| View Product: TCI America, M0006 · 25 g (opens new tab) | |
| Named grade not statedM0006 · 500 gcis identity. The 99% titration headline is not the separate GC minimum. | GC: minimum 98.0% Neutralization titration: minimum 99.0% | 500 g | $31.00USD · US public price | Not comparedGrades, assay bases, or forms differ | View Product: TCI America, M0006 · 500 g (opens new tab) | |||
| Sigma-Aldrich / MerckMaleic Acid | For synthesis800380cis identity and stereochemical InChI confirmed. Package options and public price were not exposed in retrieved product content. | HPLC: minimum 99.0 area% Acidimetric: minimum 99.0% | Package not verified | Public price not verified | Not comparedGrades, assay bases, or forms differ | Document notes: Sigma-Aldrich / Merck
| View Product: Sigma-Aldrich / Merck, 800380 (opens new tab) | |
| FUJIFILM WakoMaleic Acid | Wako Special Grade130-00492Research / further manufacturing. Japan stock does not confirm US availability. Discontinued 0.1 mol/L item excluded; the listed packages are free-acid solids. | 99.0+% (Titration) | 25 g | $20.00USD · US catalog list price | Not comparedGrades, assay bases, or forms differ | Document notes: FUJIFILM Wako
| View Product: FUJIFILM Wako, 130-00492 (opens new tab) | |
| Wako Special Grade134-00495Research / further manufacturing. Japan stock does not confirm US availability. Discontinued 0.1 mol/L item excluded; the listed packages are free-acid solids. | 99.0+% (Titration) | 500 g | $38.00USD · US catalog list price | Not comparedGrades, assay bases, or forms differ | View Product: FUJIFILM Wako, 134-00495 (opens new tab) |
TCI America
Maleic Acid
Neutralization titration: minimum 99.0%
Named grade not stated
cis identity. The 99% titration headline is not the separate GC minimum.
25 g
M0006 · 25 g- Public price
- $23.00USD · US public price
- Normalized price
- Not comparedGrades, assay bases, or forms differ
500 g
M0006 · 500 g- Public price
- $31.00USD · US public price
- Normalized price
- Not comparedGrades, assay bases, or forms differ
Documentation
Document notes: TCI America
- A product-specific certificate retrieval option was visible; no lot certificate was reviewed. Open the product page and use its certificate section.
- A current regional SDS was not verified in this pass.
- Origin-document availability was not verified. Country of origin is unverified and is not inferred.
Last checked:
Sigma-Aldrich / Merck
Maleic Acid
Acidimetric: minimum 99.0%
For synthesis
cis identity and stereochemical InChI confirmed. Package options and public price were not exposed in retrieved product content.
Package not verified
800380- Public price
- Public price not verified
- Normalized price
- Not comparedGrades, assay bases, or forms differ
Documentation
Document notes: Sigma-Aldrich / Merck
- A product-specific certificate retrieval option was visible; no lot certificate was reviewed. Open the product page and use its certificate section.
- A current regional SDS was not verified in this pass.
- Origin-document availability was not verified. Country of origin is unverified and is not inferred.
Last checked:
FUJIFILM Wako
Maleic Acid
Wako Special Grade
Research / further manufacturing. Japan stock does not confirm US availability. Discontinued 0.1 mol/L item excluded; the listed packages are free-acid solids.
25 g
130-00492- Public price
- $20.00USD · US catalog list price
- Normalized price
- Not comparedGrades, assay bases, or forms differ
500 g
134-00495- Public price
- $38.00USD · US catalog list price
- Normalized price
- Not comparedGrades, assay bases, or forms differ
Documentation
Document notes: FUJIFILM Wako
- A product-specific certificate retrieval option was visible; no lot certificate was reviewed. Open the product page and use its certificate section.
- A current regional SDS was not verified in this pass.
- Origin-document availability was not verified. Country of origin is unverified and is not inferred.
Last checked:
Documentation evidence
COA = Certificate of Analysis · SDS = Safety Data Sheet · COO = Certificate of Origin.
Lookup means a retrieval option was visible, not that a lot certificate was reviewed. Check supplier means availability or the applicable document was not verified.
Prices may vary by quantity, account, contract, geography, and availability. These products have different grades, assay bases, or forms; no normalized comparison is shown. Foreign-market prices are reference listings only. No currency conversion, mass-to-volume conversion, or ranking is applied. Confirm equivalent specifications and a current quote before comparison. [4] [5] [6]
Verification limits & placement policy
pKa: OMITTED. Compiled ECHA-attributed values are 1.94 and 6.22 at 25 °C, but the entry cites OECD 105 (a solubility guideline) and does not establish the ionization method, ionic strength or sufficient solvent context. The isolated 1.83 entry lacks conditions. Numeric comparison omitted. Water solubility: CONFLICT UNRESOLVED. HSDB lists 441 and 788 g/L at 25 °C; TCI 780 g/L at 25 °C; ICSC 78 g/100 mL without clarifying solution versus solvent-volume basis. Basis or method could matter, but the retrieved data do not establish the cause. Main numeric field omitted. Melting / heating: CONDITION-DEPENDENT. Supplier/literature melting references span roughly 130–135 °C; decomposition and reported partial isomerization make a clean boiling field misleading. Supplier package / price: OMITTED. Merck product identity and assays confirmed, but package options and public price were not exposed. No guessed package inserted.
Only the displayed identity, specification, packages, public prices and stated documentation evidence were reviewed. Current stock, lead times, shipping eligibility, contract pricing, lot certificates, and regulatory suitability are unverified.
There are no paid placements. Future paid listings will show “Sponsored” in both views; payment will not determine chemistry interpretation or imply a ranking.
07
PLAN A LARGER ORDER
Need Maleic Acid in Bulk?
Turn your requirements into a clear supplier brief.
Bulk RFQ feature — coming soon. Prototype form: submissions are not currently sent to suppliers. Use sample details to prepare an on-screen brief.
Prepare a bulk request Prototype form
08
A BUYER’S CHECKLIST
Before You Buy Maleic Acid
Selections remain only while this page is open.
09
FOR YOUR REFERENCE
Maleic Acid Technical Reference
Identity, product reference properties, and handling context.
Identification Names, formula & identifiers
- Principal CAS
- 110-16-7
- Identity focus
- Z / cis free acid
- Formula
- C₄H₄O₄
- Molecular weight
- 116.07 g/mol
- IUPAC name
- (Z)-but-2-enedioic acid
- Connectivity SMILES
- C(=CC(=O)O)C(=O)O
- Identity SMILES
- C(=C\C(=O)O)\C(=O)O
- InChI
- InChI=1S/C4H4O4/c5-3(6)1-2-4(7)8/h1-2H,(H,5,6)(H,7,8)/b2-1-
- PubChem CID
- 444266
Connectivity SMILES describes connectivity; it is not an independent stereochemical assignment. CAS and product-form distinctions are supported by the supplier listings. [1] [4] [5] [6]
Physical Properties Product references & conditions
Solid at 20 °C. Heating can cause chemical change and decomposition near the melting region; a listed decomposition temperature is not an ordinary boiling point. [13] [4] [5]
- Melting reference
- 131 °C; ICSC 1186 [14]
- Heating behavior
- ICSC reports decomposition at 135 °C, with irritating fumes including maleic anhydride on heating. Not a clean boiling constant. [14]
- Solid density
- 1.590 g/cm³ at 20 °C; CRC (2014–2015), attributed in HSDB [13]
Hydrate, concentration, stereoisomer, and temperature can change the relevant specification. Product reference data are not a reviewed lot certificate.
Acid/Base Properties Verified values & missing data
A numeric pKa was not verified for the selected identity in this review; no value is inferred. [2]
pKa: OMITTED. Compiled ECHA-attributed values are 1.94 and 6.22 at 25 °C, but the entry cites OECD 105 (a solubility guideline) and does not establish the ionization method, ionic strength or sufficient solvent context. The isolated 1.83 entry lacks conditions. Numeric comparison omitted. Water solubility: CONFLICT UNRESOLVED. HSDB lists 441 and 788 g/L at 25 °C; TCI 780 g/L at 25 °C; ICSC 78 g/100 mL without clarifying solution versus solvent-volume basis. Basis or method could matter, but the retrieved data do not establish the cause. Main numeric field omitted. Melting / heating: CONDITION-DEPENDENT. Supplier/literature melting references span roughly 130–135 °C; decomposition and reported partial isomerization make a clean boiling field misleading. Supplier package / price: OMITTED. Merck product identity and assays confirmed, but package options and public price were not exposed. No guessed package inserted.
Temperature, ionic strength, and the use of activities versus concentrations matter in quantitative work. These reference values are not buffer recipes.
Safety at a Glance Product-specific hazards
TCI and Merck classify these maleic-acid products as corrosive, harmful by ingestion or skin contact, capable of skin sensitization, and irritating to the respiratory tract. ICSC warns of irritating fumes including maleic anhydride on heating and of aquatic toxicity. Dust exposure and allergic skin reactions must not be minimized because maleate salts occur in medicines. [4] [5] [6] [14]
Hazard classifications can vary by concentration, product, supplier and jurisdiction. Review the SDS for the exact product before handling. This summary does not replace the SDS.
Supplier safety information and SDS retrieval (opens new tab)
A product-page safety classification is not verification of every regional SDS. Confirm product code, chemical form and current local document.
Review supplier documentation10
COMMON QUESTIONS
Maleic Acid FAQ
What distinguishes Maleic Acid?
Two carboxyl groups lie on the same side of the carbon–carbon double bond. Fumaric acid places them on opposite sides. The same formula and molecular weight do not establish interchangeable identity. [1]
How does it differ from Fumaric Acid?
Maleic and fumaric acids share connectivity but differ in Z/E geometry. Their thermal behavior and ionization context must be evaluated separately. Maleic anhydride is a dehydration product with a different formula; its application list is not automatically the acid’s. [7]
What must a buyer specify?
TCI M0006 specifies minimum 99% titration but minimum 98% GC. Merck 800380 specifies HPLC area and acidimetric assays separately. All displayed entries are free-acid solids; Wako’s discontinued 0.1 mol/L item is excluded. [4]
Are the listed products directly price-comparable?
No. The table retains differing grades, assay bases, forms, and markets. No normalized ranking or currency conversion is applied. [5]
What reference data still need checking?
pKa: OMITTED. Compiled ECHA-attributed values are 1.94 and 6.22 at 25 °C, but the entry cites OECD 105 (a solubility guideline) and does not establish the ionization method, ionic strength or sufficient solvent context. The isolated 1.83 entry lacks conditions. Numeric comparison omitted. Water solubility: CONFLICT UNRESOLVED. HSDB lists 441 and 788 g/L at 25 °C; TCI 780 g/L at 25 °C; ICSC 78 g/100 mL without clarifying solution versus solvent-volume basis. Basis or method could matter, but the retrieved data do not establish the cause. Main numeric field omitted. Melting / heating: CONDITION-DEPENDENT. Supplier/literature melting references span roughly 130–135 °C; decomposition and reported partial isomerization make a clean boiling field misleading. Supplier package / price: OMITTED. Merck product identity and assays confirmed, but package options and public price were not exposed. No guessed package inserted.
Can I request a bulk quote here?
The RFQ is a prototype that prepares an on-screen brief. Nothing is sent to suppliers. Confirm actual bulk terms directly with the supplier.
11
TRACE THE INFORMATION
Sources & Editorial Notes
Identity and compiled reference values are separated from supplier-specific specifications. Structural comparisons and buyer guidance are editorial interpretation. Sources were checked October 3, 2026; supplier information can change.
- PubChem · chemical identity (opens new tab)
Neutral molecular identity verified independently through PUG REST; CAS also checked on all selected supplier products.
- PubChem / HSDB · dissociation references (opens new tab)
No numeric field promoted: insufficient conditions or unresolved conflicting records.
- PubChem / HSDB · application references (opens new tab)
Attributed application records reviewed claim by claim. Free acid, intermediate, derivative and biological context are distinguished.
- TCI America · commercial product (opens new tab)
Direct product checked October 3, 2026. Identity, listed assay methods, packages, market, prices and documentation interfaces inspected. Lot certificates and stock are not verified.
- Sigma-Aldrich / Merck · commercial product (opens new tab)
Direct product checked October 3, 2026. Identity, listed assay methods, packages, market, prices and documentation interfaces inspected. Lot certificates and stock are not verified.
- FUJIFILM Wako · commercial product (opens new tab)
Direct product checked October 3, 2026. Identity, listed assay methods, packages, market, prices and documentation interfaces inspected. Lot certificates and stock are not verified.
- Fumaric Acid · identity (opens new tab)
Primary structural comparison. Practical interpretation does not establish suitability.
- Succinic Acid · identity (opens new tab)
Related identity and structural relationship.
- Malic Acid · identity (opens new tab)
Related identity and structural relationship.
- Malonic Acid · identity (opens new tab)
Related identity and structural relationship.
- Fumaric Acid · dissociation references (opens new tab)
Only independently reviewed values are promoted into the comparison; no condition-free acidity ranking.
- OpenStax · Carboxylic-acid structure and properties (opens new tab)
General carboxylate resonance, acidity and structural interpretation; not authority for this acid’s quantitative constants.
- PubChem / HSDB · attributed physical references (opens new tab)
Conditions, isomer assignments, decomposition qualifiers and unresolved conflicts reviewed; no aggregate number treated as universal.
- ILO/WHO · ICSC 1186 (opens new tab)
Chemical-specific safety and physical context; exact-product SDS remains necessary.
- Journal of Chemical Education · Maleic/fumaric hydrogen bonding (opens new tab)
Publisher abstract reviewed: separate intra/intermolecular hydrogen-bonding and first/second ionization comparisons. Full article not retrieved.
Review limits
pKa: OMITTED. Compiled ECHA-attributed values are 1.94 and 6.22 at 25 °C, but the entry cites OECD 105 (a solubility guideline) and does not establish the ionization method, ionic strength or sufficient solvent context. The isolated 1.83 entry lacks conditions. Numeric comparison omitted. Water solubility: CONFLICT UNRESOLVED. HSDB lists 441 and 788 g/L at 25 °C; TCI 780 g/L at 25 °C; ICSC 78 g/100 mL without clarifying solution versus solvent-volume basis. Basis or method could matter, but the retrieved data do not establish the cause. Main numeric field omitted. Melting / heating: CONDITION-DEPENDENT. Supplier/literature melting references span roughly 130–135 °C; decomposition and reported partial isomerization make a clean boiling field misleading. Supplier package / price: OMITTED. Merck product identity and assays confirmed, but package options and public price were not exposed. No guessed package inserted.
This informational prototype is not a supplier, quotation service, or endorsement of a product’s fitness for an application. Buyers should verify the applicable specification, certification, and regulatory requirements for their intended use.