> Category: pH Indicator / Analytical Reagent | Molecular Formula: C20H14O4 | Molecular Weight: 318.3 | CAS: 77-09-8
What Is Phenolphthalein Used For?
Phenolphthalein (CAS 77-09-8) is a ph indicator / analytical reagent primarily used in acid-base titration. Phenolphthalein remains the most recognized acid-base indicator worldwide, used in millions of titrations annually across quality control laboratories, educational institutions, and industrial settings. Its sharply defined color transition (colorless to pink over pH 8.2-10.0) provides an unambiguous endpoint in strong acid-strong base and weak acid-strong base titrations. Beyond titration, it serves critical roles in concrete carbonation depth measurement and as a key component of Kastle-Meyer presumptive blood tests in forensic science.
With a molecular formula of C20H14O4 and molecular weight of 318.3 g/mol [001], Phenolphthalein is white to pale yellow crystalline powder and soluble in ethanol (50 mg/ml); practically insoluble in water; soluble in dilute alkali with pink color [002]. The global market for this compound class was valued at $42 million (2023) phenolphthalein; $185.1 million pH indicators (2025), growing at a CAGR of 5.1% (pH indicators) [003].
How Does Phenolphthalein Work in Chemical Reactions?
The mechanism of action of Phenolphthalein depends on its structural features. With InChIKey KJFMBFZCATUALV-UHFFFAOYSA-N [001], Phenolphthalein functions through Phenolphthalein remains the most recognized acid-base indicator worldwide, used in millions of titrations annually acros....
Key mechanistic features include:
- Structural specificity: The molecular architecture of Phenolphthalein (IUPAC: 3,3-bis(4-hydroxyphenyl)-2-benzofuran-1-one [001]) determines its reactivity profile and selectivity
- Solubility profile: Soluble in ethanol (50 mg/mL); practically insoluble in water; soluble in dilute alkali with pink color [002], enabling compatibility with diverse reaction conditions
- Functional group tolerance: Compatible with a wide range of functional groups commonly encountered in multi-step synthesis
For industrial applications, Phenolphthalein has been optimized for scalability. The compound's white to pale yellow crystalline powder facilitates handling, and its well-characterized properties enable reproducible process chemistry across batch sizes ranging from milligram to kilogram scale.
What Are the Key Applications of Phenolphthalein?
Phenolphthalein serves critical roles across multiple chemical sectors [004]:
- Acid-base titration indicator (colorless pH<8.2, pink pH>10.0)
- Concrete carbonation testing
- Forensic science (Kastle-Meyer test for blood)
- Educational chemistry demonstrations
The diversity of applications reflects the compound's versatility. In pharmaceutical synthesis, Phenolphthalein enables key bond-forming reactions that would be difficult or impossible with alternative reagents. In materials chemistry, it provides access to polymers and advanced materials with tailored properties.
What Are the Physical and Chemical Properties of Phenolphthalein?
Understanding the physical properties of Phenolphthalein (CAS 77-09-8) is essential for safe handling and optimal experimental design [001] [002]:
| Property | Value |
|---|---|
| CAS Number | 77-09-8 |
| Molecular Formula | C20H14O4 |
| Molecular Weight | 318.3 g/mol |
| IUPAC Name | 3,3-bis(4-hydroxyphenyl)-2-benzofuran-1-one |
| InChIKey | KJFMBFZCATUALV-UHFFFAOYSA-N |
| Appearance | White to pale yellow crystalline powder |
| Melting Point | 258-263 °C |
| Density | 1.30 g/cm³ |
Solubility characteristics: Soluble in ethanol (50 mg/mL); practically insoluble in water; soluble in dilute alkali with pink color [002]. These properties dictate the choice of reaction medium, workup procedures, and purification strategies when working with Phenolphthalein.
What Is the Market Outlook for Phenolphthalein?
The global market for this class of compounds demonstrates robust growth [003]. The market was valued at $42 million (2023) phenolphthalein; $185.1 million pH indicators (2025), with a compound annual growth rate (CAGR) of 5.1% (pH indicators) [003].
Three forces drive demand:
- Pharmaceutical R&D expansion: Over 60% of the demand for high-purity ph indicator / analytical reagents originates from pharmaceutical research and manufacturing, driven by the increasing pipeline of small-molecule drug candidates
- Asia-Pacific manufacturing growth: China and India account for approximately 45% of global consumption, reflecting the migration of pharmaceutical intermediate manufacturing to the region [003]
- Green chemistry adoption: The shift toward sustainable synthesis methods favors reagents with favorable E-factors and aqueous compatibility
The market report by PMarketResearch, pH Indicator Market Report 2026 projects continued expansion through 2032, driven by these structural demand drivers [003].
How Should Phenolphthalein Be Safely Handled and Stored?
Proper handling of Phenolphthalein requires attention to standard laboratory safety protocols. Key considerations:
- Storage: Store in a cool, dry, well-ventilated area. Keep container tightly closed when not in use
- Personal protective equipment (PPE): Wear appropriate gloves (nitrile recommended), safety goggles, and lab coat
- Ventilation: Use in a fume hood or well-ventilated area
- Incompatibilities: Avoid contact with strong oxidizing agents and incompatible materials
Always consult the Safety Data Sheet (SDS) from your supplier before handling. The SDS provides detailed information on hazards, first aid measures, firefighting procedures, and disposal considerations specific to the grade and formulation you are using [002].
Frequently Asked Questions About Phenolphthalein
What is the CAS number of Phenolphthalein?
The CAS Registry Number of Phenolphthalein is 77-09-8. This unique identifier is assigned by the Chemical Abstracts Service and is recognized globally for unambiguous chemical identification [001].
Is Phenolphthalein water-soluble?
Soluble in ethanol (50 mg/mL); practically insoluble in water; soluble in dilute alkali with pink color. Soluble in ethanol (50 mg/mL); practically insoluble in water; soluble in dilute alkali with pink color [002]. This solubility profile is critical for selecting appropriate reaction solvents and workup conditions.
What is the molecular weight of Phenolphthalein?
The molecular weight of Phenolphthalein (77-09-8) is 318.3 g/mol, based on its molecular formula C20H14O4 [001].
Where can I buy Phenolphthalein with fast shipping?
Phenolphthalein is widely available from major chemical suppliers including Sigma-Aldrich (catalog #105962), Thermo Fisher Scientific, TCI America, and other regional distributors. For research quantities, most suppliers offer next-day delivery in major markets. Bulk and custom quantities typically require 1-4 weeks lead time. CoreyChem also stocks Phenolphthalein at competitive prices with global shipping.
What are the main applications of Phenolphthalein in industry?
The primary industrial applications of Phenolphthalein include: Acid-base titration indicator (colorless pH<8.2, pink pH>10.0); Concrete carbonation testing; Forensic science (Kastle-Meyer test for blood); and Educational chemistry demonstrations [004].
What is the difference between Phenolphthalein and similar reagents?
Unlike structurally related alternatives, Phenolphthalein offers unique structural and reactivity features. This differentiated performance profile makes it the preferred choice for the specific applications listed above [004].
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Where to Buy Phenolphthalein (CAS 77-09-8)
Phenolphthalein is available in the CoreyChem catalog. [View product page →](https://careerchemical.com/product/77-09-8)
CoreyChem supplies Phenolphthalein to research laboratories and industrial customers worldwide. Contact our sales team for bulk pricing and custom packaging options.
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References & Sources
https://pmarketresearch.com/chemi/ph-indicator-market/
https://www.sigmaaldrich.com/US/en/product/aldrich/105962
