Fluorescein (CAS NO.2321-07-5) was first synthesized by Adolf von Baeyer in 1871.

Reported in EPA TSCA Inventory. EPA Genetic Toxicology Program.

The Spiro[isobenzofuran-1(3H),9'-[9H]xanthen]-3-one,3',6'-dihydroxy-, with the CAS registry number 2321-07-5, is also known as 3',6'-Dihydroxyspiro[isobenzofuran-1(3H),9'-[9H]xanthen]-3-one. It belongs to the product categories of E-F Fluorescent Probes, Labels, Particles and Stains; Fluorescein and Derivatives; Fluorescent Labels; Stains and Dyes; Aromatics; Fluorescent Labels & Indicators; Heterocycles; Intermediates & Fine Chemicals; Pharmaceuticals. Its EINECS number is 219-031-8. This chemical's molecular formula is C₂₀H₁₂O₅ and molecular weight is 332.31. What's more, its systematic name is 3',6'-dihydroxy-3H-spiro[2-benzofuran-1,9'-xanthen]-3-one. Its classification codes are: (1)Coloring Agents; (2)Contrast media; (3)Diagnostic aid [corneal trauma indicator]; (4)Fluorescent Dyes; (5)Indicators and Reagents; (6)Luminescent Agents; (7)Mutation data. It is a phthalic indicator dye that appears yellow-green in normal tear film and bright green in a more alkaline medium, and is used therapeutically as a diagnostic aid in corneal injuries and corneal trauma. It has been approved by FDA for use in externally applied drugs and cosmetics. It should be sealed and stored in a cool and dry place. Moreover, it should be protected from oxides.

Physical properties of Spiro[isobenzofuran-1(3H),9'-[9H]xanthen]-3-one,3',6'-dihydroxy- are: (1)ACD/LogP: 2.68; (2)# of Rule of 5 Violations: 0; (3)ACD/LogD (pH 5.5): 2.682; (4)ACD/LogD (pH 7.4): 2.677; (5)ACD/BCF (pH 5.5): 64.328; (6)ACD/BCF (pH 7.4): 63.627; (7)ACD/KOC (pH 5.5): 685.565; (8)ACD/KOC (pH 7.4): 678.096; (9)#H bond acceptors: 5; (10)#H bond donors: 2; (11)#Freely Rotating Bonds: 2; (12)Polar Surface Area: 75.99 Å²; (13)Index of Refraction: 1.792; (14)Molar Refractivity: 87.995 cm³; (15)Molar Volume: 207.439 cm³; (16)Polarizability: 34.884×10^-24cm³; (17)Surface Tension: 90.403 dyne/cm; (18)Density: 1.602 g/cm³; (19)Flash Point: 232.645 °C; (20)Enthalpy of Vaporization: 95.37 kJ/mol; (21)Boiling Point: 620.841 °C at 760 mmHg; (22)Vapour Pressure: 0 mmHg at 25°C.

Preparation: this chemical can be prepared by phthalic acid anhydride and benzene-1,3-diol at the temperature of 160 °C. This reaction will need reagent conc. H₂SO₄ with the reaction time of 5 min. The yield is about 88%.

Uses of Spiro[isobenzofuran-1(3H),9'-[9H]xanthen]-3-one,3',6'-dihydroxy-: it can be used to produce 2-(2,4-dihydroxy-benzoyl)-benzoic acid by heating. It will need reagent KOH and solvent H₂O with the reaction time of 5 hours. The yield is about 86%.

When you are using this chemical, please be cautious about it as the following:
It is irritating to eyes, respiratory system and skin and may cause sensitisation by skin contact. In case of contact with eyes, you should rinse immediately with plenty of water and seek medical advice. You should take off immediately all contaminated clothing. You should not breathe dust. When using it, you must avoid contact with eyes and need wear suitable protective clothing, gloves and eye/face protection.

You can still convert the following datas into molecular structure:
(1)SMILES: c1ccc2c(c1)C(=O)OC23c4ccc(cc4Oc5c3ccc(c5)O)O
(2)Std. InChI: InChI=1S/C20H12O5/c21-11-5-7-15-17(9-11)24-18-10-12(22)6-8-16(18)20(15)14-4-2-1-3-13(14)19(23)25-20/h1-10,21-22H
(3)Std. InChIKey: GNBHRKFJIUUOQI-UHFFFAOYSA-N

The toxicity data is as follows: