Organic-synthesis intermediate
Sigma H20008 documents 3-hydroxybenzoic acid as a precursor in syntheses of biologically investigated small molecules, including oxadiazole analogs. [5]
01
THE ESSENTIALS
3-Hydroxybenzoic Acid in 30 Seconds
COOH defines ring position 1 and OH occupies position 3. There is one carboxyl group, not two; the phenolic proton is a separate acid-base site. The neutral structure is achiral.
3-Hydroxybenzoic acid is the meta isomer, with one phenolic OH and one COOH group. Its positional identity matters in synthesis and must not be replaced with the better-known ortho salicylic acid. [1] [3]
Safety at a glance — TCI identifies harmful ingestion and skin/eye irritation; Sigma also identifies respiratory irritation. Control inhalable powder and contact exposure according to the exact-product SDS. Research into derivatives does not reduce the raw-acid hazards or establish safe therapeutic use. [4] [5] [6]
A condensed structural formula keeps the functional groups visible. [1]
02
GO A LITTLE DEEPER
Understanding 3-Hydroxybenzoic Acid
THE SIMPLE EXPLANATION
The functional groups
COOH defines ring position 1 and OH occupies position 3. There is one carboxyl group, not two; the phenolic proton is a separate acid-base site. The neutral structure is achiral. [1]
A LITTLE DEEPER
What the structure changes
Meta substitution differs from ortho adjacency and para alignment. In particular, the meta OH is not arranged for the adjacent intramolecular hydrogen-bond relationship of salicylic acid. Do not transfer salicylic-acid acidity constants or formulated skin-use claims to this isomer. [1] [12]
Technical detail Identity, dissociation & specification
Connectivity and neutral formula identify this acid. Positional isomers, water-containing products, salts and esters require their own specifications. Measured reference conditions, assay methods and unresolved discrepancies remain visible. [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 3-Hydroxybenzoic Acid Compares
Similar names and functional groups do not mean interchangeable chemicals.
SIDE-BY-SIDE COMPARISON
3-Hydroxybenzoic Acid vs 4-Hydroxybenzoic Acid
Meta phenolic monocarboxylic acid
versusPara phenolic monocarboxylic acid
Fixed comparison for this prototype. Acid selectors are disabled; additional comparisons are coming later.
| Property | 3-Hydroxybenzoic Acid | 4-Hydroxybenzoic Acid |
|---|---|---|
| Molecular formula | C₇H₆O₃ [1] | C₇H₆O₃ [7] |
| Molecular weight | 138.12 g/mol [1] | 138.12 g/mol [7] |
| Carbon atoms | 7 [1] | 7 [7] |
| Carboxyl groups | 1 [1] | 1 [7] |
| Structure | 3-HO–C₆H₄–COOH [1] | 4-HO–C₆H₄–COOH [7] |
| Chemical family | Meta phenolic monocarboxylic acid [1] | Para phenolic monocarboxylic acid [7] |
| Identity focus | Neutral free acid; water and derivatives specified separately [1] | Neutral free acid; water and derivatives specified separately [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.
When Might You Choose One Instead of the Other?
Choose the 3-isomer for a method specifying its meta hydroxyl and carboxyl arrangement; choose the 4-isomer for a para target. Require an identity test that distinguishes positions, plus method-specific assay and impurity limits. [1] [3] [7]
Specified starting material
3-Hydroxybenzoic Acid
Match 3-HO–C₆H₄–COOH and the method’s required chemical form.
4-Hydroxybenzoic Acid
Match 4-HO–C₆H₄–COOH; 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 3-Hydroxybenzoic Acid Used For?
Organic-synthesis intermediate
Sigma H20008 documents 3-hydroxybenzoic acid as a precursor in syntheses of biologically investigated small molecules, including oxadiazole analogs. This verifies intermediate use, not that the free acid is an approved therapeutic agent. [5]
06
SOURCE WITH CONTEXT
3-Hydroxybenzoic Acid Suppliers
Compare specific products and package options. Listings are not ranked recommendations.
3 suppliers · 3 products · 7 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 reports HPLC area% and neutralization titration separately; Sigma’s 99% method is unstated; Thermo’s 99% headline has a minimum 98.5% HPLC specification. None is a verified pharma or cosmetic ingredient grade. Positional identity is independent of total acid assay.
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 America3-Hydroxybenzoic Acid | Named grade not statedH0205 · 25 g | HPLC: minimum 98.0 area% Neutralization titration: minimum 98.0% | 25 g | $21.00USD · US public price | Not comparedGrades, assay bases, or forms differ | Document notes: TCI America
| View Product: TCI America, H0205 · 25 g (opens new tab) | |
| Named grade not statedH0205 · 100 g | HPLC: minimum 98.0 area% Neutralization titration: minimum 98.0% | 100 g | $44.00USD · US public price | Not comparedGrades, assay bases, or forms differ | View Product: TCI America, H0205 · 100 g (opens new tab) | |||
| Named grade not statedH0205 · 500 g | HPLC: minimum 98.0 area% Neutralization titration: minimum 98.0% | 500 g | $164.00USD · US public price | Not comparedGrades, assay bases, or forms differ | View Product: TCI America, H0205 · 500 g (opens new tab) | |||
| Sigma-Aldrich3-Hydroxybenzoic Acid | ReagentPlusH20008-5G500 g list price shown; promotional USD 182.25 was also displayed. | 99%; method not stated | 5 g | $40.80USD · US public list price | Not comparedGrades, assay bases, or forms differ | Document notes: Sigma-Aldrich
| View Product: Sigma-Aldrich, H20008-5G (opens new tab) | |
| ReagentPlusH20008-100G500 g list price shown; promotional USD 182.25 was also displayed. | 99%; method not stated | 100 g | $67.90USD · US public list price | Not comparedGrades, assay bases, or forms differ | View Product: Sigma-Aldrich, H20008-100G (opens new tab) | |||
| ReagentPlusH20008-500G500 g list price shown; promotional USD 182.25 was also displayed. | 99%; method not stated | 500 g | $243.00USD · US public list price | Not comparedGrades, assay bases, or forms differ | View Product: Sigma-Aldrich, H20008-500G (opens new tab) | |||
| Thermo Scientific Chemicals3-Hydroxybenzoic Acid | Research use only; named grade not stated120981000List USD 62.00; online-exclusive USD 52.65 displayed with December 28, 2026 end date. A generic documents link does not verify a product-specific lot COA interface. | 99% headline; HPLC minimum 98.5% | 100 g | $62.00USD · US public list price | Not comparedGrades, assay bases, or forms differ | COACheck supplierSDSCheck supplierCOOCheck supplier Document notes: Thermo Scientific Chemicals
| View Product: Thermo Scientific Chemicals, 120981000 (opens new tab) |
TCI America
3-Hydroxybenzoic Acid
Neutralization titration: minimum 98.0%
Named grade not stated
25 g
H0205 · 25 g- Public price
- $21.00USD · US public price
- Normalized price
- Not comparedGrades, assay bases, or forms differ
100 g
H0205 · 100 g- Public price
- $44.00USD · US public price
- Normalized price
- Not comparedGrades, assay bases, or forms differ
500 g
H0205 · 500 g- Public price
- $164.00USD · 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
3-Hydroxybenzoic Acid
ReagentPlus
500 g list price shown; promotional USD 182.25 was also displayed.
5 g
H20008-5G- Public price
- $40.80USD · US public list price
- Normalized price
- Not comparedGrades, assay bases, or forms differ
100 g
H20008-100G- Public price
- $67.90USD · US public list price
- Normalized price
- Not comparedGrades, assay bases, or forms differ
500 g
H20008-500G- Public price
- $243.00USD · US public list price
- Normalized price
- Not comparedGrades, assay bases, or forms differ
Documentation
Document notes: Sigma-Aldrich
- 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:
Thermo Scientific Chemicals
3-Hydroxybenzoic Acid
Research use only; named grade not stated
List USD 62.00; online-exclusive USD 52.65 displayed with December 28, 2026 end date. A generic documents link does not verify a product-specific lot COA interface.
100 g
120981000- Public price
- $62.00USD · US public list price
- Normalized price
- Not comparedGrades, assay bases, or forms differ
Documentation
COACheck supplierSDSCheck supplierCOOCheck supplier
Document notes: Thermo Scientific Chemicals
- COA availability was not verified.
- 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
Melting range: CONDITION-DEPENDENT. Product specification limits and literature ranges are different types of data; none is a reviewed lot result. pKa / water solubility: OMITTED. Fully attributed numerical measurements with necessary conditions were not verified for this isomer; values from salicylic or para acid are not substituted. Boiling / density: OMITTED. Matched measured values with phase/pressure context were not established.
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 3-Hydroxybenzoic 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 3-Hydroxybenzoic Acid
Selections remain only while this page is open.
09
FOR YOUR REFERENCE
3-Hydroxybenzoic Acid Technical Reference
Identity, product reference properties, and handling context.
Identification Names, formula & identifiers
- Principal CAS
- 99-06-9
- Identity focus
- Neutral free acid; water and derivatives specified separately
- Formula
- C₇H₆O₃
- Molecular weight
- 138.12 g/mol
- IUPAC name
- 3-hydroxybenzoic acid
- Connectivity SMILES
- C1=CC(=CC(=C1)O)C(=O)O
- Identity SMILES
- C1=CC(=CC(=C1)O)C(=O)O
- InChI
- InChI=1S/C7H6O3/c8-6-3-1-2-5(4-6)7(9)10/h1-4,8H,(H,9,10)
- PubChem CID
- 7420
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. Supplier melting specifications and literature ranges refer to this meta identity. [13] [4] [5]
- Melting specifications
- TCI H0205: 201–207 °C; Thermo: 201–205 °C. Sigma literature reference: 200–203 °C. [4]
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]
Melting range: CONDITION-DEPENDENT. Product specification limits and literature ranges are different types of data; none is a reviewed lot result. pKa / water solubility: OMITTED. Fully attributed numerical measurements with necessary conditions were not verified for this isomer; values from salicylic or para acid are not substituted. Boiling / density: OMITTED. Matched measured values with phase/pressure context were not established.
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 identifies harmful ingestion and skin/eye irritation; Sigma also identifies respiratory irritation. Control inhalable powder and contact exposure according to the exact-product SDS. Research into derivatives does not reduce the raw-acid hazards or establish safe therapeutic use. [4] [5] [6]
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
3-Hydroxybenzoic Acid FAQ
What distinguishes 3-Hydroxybenzoic Acid?
COOH defines ring position 1 and OH occupies position 3. There is one carboxyl group, not two; the phenolic proton is a separate acid-base site. The neutral structure is achiral. [1]
How does it differ from 4-Hydroxybenzoic Acid?
The meta and para acids share formula and mass but have different OH attachment positions. That changes synthetic connectivity and electronic effects; it does not justify a condition-free numerical acidity or solubility ranking. [7]
What must a buyer specify?
TCI reports HPLC area% and neutralization titration separately; Sigma’s 99% method is unstated; Thermo’s 99% headline has a minimum 98.5% HPLC specification. None is a verified pharma or cosmetic ingredient grade. Positional identity is independent of total acid assay. [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?
Melting range: CONDITION-DEPENDENT. Product specification limits and literature ranges are different types of data; none is a reviewed lot result. pKa / water solubility: OMITTED. Fully attributed numerical measurements with necessary conditions were not verified for this isomer; values from salicylic or para acid are not substituted. Boiling / density: OMITTED. Matched measured values with phase/pressure context were not established.
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 · 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.
- Thermo Scientific Chemicals · 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.
- 4-Hydroxybenzoic Acid · identity (opens new tab)
Primary structural comparison. Practical interpretation does not establish suitability.
- Salicylic Acid · identity (opens new tab)
Related identity and structural relationship.
- Benzoic Acid · identity (opens new tab)
Related identity and structural relationship.
- Gallic Acid · identity (opens new tab)
Related identity and structural relationship.
- 4-Hydroxybenzoic 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)
Attributed references and conditions reviewed; unsupported estimates and cross-isomer data excluded.
Review limits
Melting range: CONDITION-DEPENDENT. Product specification limits and literature ranges are different types of data; none is a reviewed lot result. pKa / water solubility: OMITTED. Fully attributed numerical measurements with necessary conditions were not verified for this isomer; values from salicylic or para acid are not substituted. Boiling / density: OMITTED. Matched measured values with phase/pressure context were not established.
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.