Sodium p-Chlorobenzoate: Properties, Uses & Lab Guide

Sodium p-chlorobenzoate is the sodium salt of 4-chlorobenzoic acid, a white crystalline aromatic carboxylate widely employed as a synthetic intermediate, analytical reference standard, and tool compound in biochemical and pharmaceutical research.

IUPAC Name

Sodium 4-chlorobenzoate

Molecular Formula

C₇H₄ClNaO₂

Molecular Weight

178.55 g/mol

CAS Number

3686-66-6

Appearance

White to off-white crystalline powder

Solubility

Soluble in water; sparingly soluble in ethanol

Storage Condition

Store at room temperature in a cool, dry place away from light

Available SKU

S1069968 — Aladdin Scientific

Chemical Identity and Physical Properties

Sodium p-chlorobenzoate (CAS 3686-66-6; molecular formula C₇H₄ClNaO₂; MW 178.55 g/mol) is the monosodium salt of 4-chlorobenzoic acid. The compound features a benzene ring bearing a para-chloro substituent and a carboxylate anion coordinated to a sodium cation. In the solid state it appears as a white to off-white crystalline powder with no significant odor. The ionic nature of the salt confers good aqueous solubility, making it convenient for preparing buffered stock solutions in biological assay formats. Its melting behavior is typically observed above 300 °C (decomposition), consistent with an ionic lattice. The compound is stable under ambient conditions when stored in a sealed container away from moisture and direct light.

The presence of the electron-withdrawing chloro group at the para position modestly lowers the pKa of the parent acid relative to unsubstituted benzoic acid, a property that influences its reactivity as a synthetic building block and its partitioning behavior in biological systems.

Research Applications

Synthetic Chemistry: Sodium p-chlorobenzoate serves as a versatile building block in organic synthesis. The carboxylate functionality participates in coupling reactions, esterification (after acidification to the free acid), and nucleophilic acyl substitution, while the para-chloro group is amenable to transition-metal-catalyzed cross-coupling reactions (e.g., Suzuki, Negishi) for the construction of biaryl or functionalized aromatic scaffolds commonly encountered in medicinal chemistry programs.

Biochemical and Microbiological Research: Aromatic benzoate salts have been studied as model substrates for bacterial aromatic-ring-cleavage pathways and as reference compounds in biodegradation studies. Sodium p-chlorobenzoate is frequently used as a co-substrate or model pollutant in environmental microbiology to assess the metabolic capacity of soil or aquatic microorganisms toward halogenated aromatics.

Analytical Reference Standards: The compound is used as a reference material in HPLC method development and validation, and as an internal standard candidate in mass spectrometric analyses of related halogenated benzoate analytes.

Pharmaceutical Research: Para-chlorobenzoate moieties appear in pharmacophore libraries; the sodium salt form provides a water-soluble, non-hygroscopic reagent for exploratory medicinal chemistry screens and solubility studies.

Handling, Safety, and Storage

Personal Protective Equipment (PPE): Standard laboratory precautions apply. Wear appropriate nitrile or latex gloves, safety spectacles or goggles, and a lab coat when handling sodium p-chlorobenzoate. In operations that may generate dust (e.g., weighing bulk powder), use a suitable dust mask or work inside a ventilated fume hood.

First Aid Measures: In case of skin or eye contact, flush thoroughly with copious water for at least 15 minutes and seek medical advice if irritation persists. If ingested accidentally, do not induce vomiting; seek medical attention. If inhaled in significant quantities, remove the person to fresh air.

Storage: Store in a tightly closed container at room temperature (15–25 °C) in a cool, dry location away from direct sunlight, strong oxidizers, and strong acids. Under these conditions, the compound is expected to be stable for an extended period. Keep the container sealed to prevent moisture uptake.

Disposal: Dispose of waste material in accordance with local environmental regulations for halogenated organic compounds. Do not discharge into drains or waterways without appropriate treatment.

Note: Always consult the current Safety Data Sheet (SDS) supplied with the product before use.

Solution Preparation and Practical Tips

Preparing Aqueous Stock Solutions: Sodium p-chlorobenzoate dissolves readily in deionized or distilled water. For a 100 mM stock solution, dissolve 178.6 mg of the compound in approximately 8 mL of water, adjust pH if required with dilute NaOH or HCl, and make up to 10 mL final volume. Filter through a 0.22 µm membrane filter for sterile applications. Solutions should be prepared fresh or stored at 4 °C for short-term use.

Compatibility: The compound is compatible with common biological buffers (PBS, HEPES, Tris) at physiological pH. Avoid strongly acidic conditions (pH < 2), which may cause precipitation of the free acid form (pKa of parent 4-chlorobenzoic acid ≈ 3.99).

Weighing Accuracy: Because small amounts of surface moisture may be absorbed upon prolonged air exposure, equilibrate the container to room temperature before opening, and weigh rapidly when high precision is required. For critical quantitative work, consider drying the material at 60 °C under vacuum for 2 h prior to use.

HPLC Analysis: When using the compound as an analytical standard, prepare working standards in the mobile-phase solvent to minimize solubility artifacts. UV detection at 235–240 nm is suitable given the aromatic chromophore.

Ordering and Product Specifications

Aladdin Scientific offers sodium p-chlorobenzoate under SKU S1069968. The product is supplied as a dry crystalline powder with documented purity. Detailed specifications including purity grade, lot-specific certificate of analysis (CoA), and SDS are available on the product page or upon request from our technical support team.

For bulk quantities, custom packaging, or specific purity requirements, please contact Aladdin Scientific sales representatives directly. Orders can be placed through the Aladdin Scientific website, by purchase order, or through authorised distributors. Standard shipping conditions at ambient temperature apply; expedited shipping options are available.

Researchers requiring documentation for regulatory or quality-assurance purposes may request a CoA, SDS, or method of analysis. Aladdin Scientific's quality management system ensures batch-to-batch consistency for reliable experimental reproducibility.

Frequently asked questions

What is sodium p-chlorobenzoate used for in the laboratory?

Sodium p-chlorobenzoate is used as a synthetic intermediate in organic chemistry, as a model substrate or reference compound in biodegradation and environmental microbiology studies, and as an analytical reference standard for HPLC or mass spectrometric methods. Its water-soluble salt form also makes it convenient for preparing defined aqueous solutions in biochemical assays.

How should sodium p-chlorobenzoate be dissolved for biological assays?

The compound dissolves readily in deionized water or standard biological buffers such as PBS or HEPES at physiological pH. Avoid strongly acidic conditions (pH below approximately 2) to prevent precipitation of the free acid. For sterile applications, filter the prepared solution through a 0.22 µm membrane filter. Freshly prepared solutions or those stored at 4 °C are recommended for best results.

What is the CAS number and molecular weight of sodium p-chlorobenzoate?

Sodium p-chlorobenzoate has the CAS number 3686-66-6 and a molecular weight of 178.55 g/mol. Its molecular formula is C₇H₄ClNaO₂.

What storage conditions are recommended for sodium p-chlorobenzoate?

Store in a tightly sealed container at room temperature (15–25 °C) in a cool, dry place away from direct sunlight, strong oxidizers, and strong acids. Under these conditions, the compound is expected to remain stable for an extended period. Always check the product label and SDS for the most current storage recommendations.

Is sodium p-chlorobenzoate the same as 4-chlorobenzoic acid?

No. Sodium p-chlorobenzoate (CAS 3686-66-6) is the sodium salt of 4-chlorobenzoic acid (CAS 74-11-3). The salt form has improved water solubility compared to the free acid and a higher apparent melting/decomposition point. For applications requiring the free acid, the salt can be acidified in solution, but the two forms are distinct chemical entities with different CAS numbers and physical properties.

References

1. National Center for Biotechnology Information. PubChem Compound Summary for Sodium 4-chlorobenzoate. PubChem.
2. Clayden J, Greeves N, Warren S. Organic Chemistry, 2nd ed. Oxford University Press, 2012. (General reference for aromatic carboxylate chemistry and cross-coupling reactions.)
3. Reineke W, Knackmuss HJ. Microbial metabolism of haloaromatics: isolation and properties of a chlorobenzene-degrading bacterium. Applied and Environmental Microbiology, 1984.

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