1. Introduction of 3,4-Dihydroxy-3-cyclobutene-1,2-dione
3,4-Dihydroxy-3-cyclobutene-1,2-dione is an organic compound with the formula C₄H₂O₄. With the CAS registry number 2892-51-5, 3,4-Dihydroxy-3-cyclobutene-1,2-dione is also named as Squaric acid; 1,2-Dihydroxycyclobutene-3,4-dione. The product's categories are cyclic Compounds; Organic Acids; Cyclobutanes & Cyclobutenes; Simple 4-Membered Ring Compounds. Besides, 3,4-Dihydroxy-3-cyclobutene-1,2-dione is a white powder, which should be stored in a closed cool and dry place. Medically, squaric acid dibutylester is used for the treatment of warts. Squaric acid dibutylester is also used treating alopecia areata or alopecia totalis/universalis (autoimmune hair loss) through topical immunotherapy involving the production of an allergic rash.

2. Properties of 3,4-Dihydroxy-3-cyclobutene-1,2-dione
The 3,4-Dihydroxy-3-cyclobutene-1,2-dione Physical properties about Squaric acid are: (1)ACD/BCF (pH 5.5): 1; (2)ACD/BCF (pH 7.4): 1; (3)ACD/KOC (pH 5.5): 1; (4)ACD/KOC (pH 7.4): 1; (5)#H bond acceptors: 4; (6)#H bond donors: 2; (7)#Freely Rotating Bonds: 2; (8)Polar Surface Area: 74.6 Å²; (9)Index of Refraction: 1.872; (10)Molar Refractivity: 21.485 cm³; (11)Molar Volume: 47.225 cm³; (12)Polarizability: 8.517×10^-24cm³; (13)Surface Tension: 235.742 dyne/cm; (14)Density: 2.415 g/cm³; (15)Flash Point: 119.84 °C; (16)Enthalpy of Vaporization: 56.725 kJ/mol; (17)Boiling Point: 250.963 °C at 760 mmHg; (18)Vapour Pressure: 0.003 mmHg at 25°C.

3. Structure Descriptors of 3,4-Dihydroxy-3-cyclobutene-1,2-dione
(1)SMILES: c1(c(c(=O)c1=O)O)O
(2)InChI: InChI=1/C4H2O4/c5-1-2(6)4(8)3(1)7/h5-6H
(3)InChIKey: PWEBUXCTKOWPCW-UHFFFAOYAC
(4)Std. InChI: InChI=1S/C4H2O4/c5-1-2(6)4(8)3(1)7/h5-6H
(5)Std. InChIKey: PWEBUXCTKOWPCW-UHFFFAOYSA-N

4. Safety Information of 3,4-Dihydroxy-3-cyclobutene-1,2-dione
When you are using this chemical, please be cautious about it as the following:
It may cause sensitisation by skin contact. In case of contact with eyes, rinse immediately with plenty of water and seek medical advice. Besides, this chemical is irritating to eyes, respiratory system and skin. When you are using it, wear suitable gloves and eye/face protection.

5. Preparation of 3,4-Dihydroxy-3-cyclobutene-1,2-dione
3,4-Dihydroxy-3-cyclobutene-1,2-dione can be prepared by N1-(2-Chlor-3,4-dioxo-1-cyclobutenyl)-N1,N2-diphenylchlorformamidin. This reaction will need reagent H₂O and solvent dioxane. The reaction time is 14 days at ambient temperature. The yield is about 66%.


6. Use of 3,4-Dihydroxy-3-cyclobutene-1,2-dione
3,4-Dihydroxy-3-cyclobutene-1,2-dione can be used to produce diethoxy-cyclobutenedione by heating. The reaction time is 4.5 hours.