DietDiethyl squarate , with cas registry number of 5231-87-8, is also called Squaric acid diethyl ester ; 3,4-Diethoxy-3-cyclobutene-1,2-dione ; 3,4-Diethoxycyclobut-3-ene-1,2-dione . Its IUPAC name is called 3,4-diethoxycyclobut-3-ene-1,2-dione . Its systematic name is also called 3,4-Diethoxycyclobut-3-ene-1,2-dione with the SMILES of O=C1C(\OCC)=C(\OCC)C1=O according to its molecular structure. DietDiethyl squarate is classified to the product categories of Cyclobutanes & Cyclobutenes; Simple 4-Membered Ring Compounds; Ring Systems.

  The physical properties of DietDiethyl squarate include: (1) H bond acceptors: 4; (2) H bond donors: 0; (3) Freely Rotating Bonds: 4; (4) Index of Refraction: 1.477; (5) Molar Refractivity: 40.2 cm³; (6) Molar Volume: 142.2 cm³; (7) Surface Tension: 37.4 dyne/cm; (8) Enthalpy of Vaporization: 56.78 kJ/mol; (9) Vapour Pressure: 0.000226 mmHg at 25°C; (10) Refractive index: n20/D 1.509(lit.). This compound irritates to eyes, respiratory system and skin and may cause sensitization by inhalation and skin contact. When use it, wear suitable gloves and eye/face protection and avoid contact with skin. If contact with eyes, rinse immediately with plenty of water and seek medical advice. After use it, keep container tightly closed and store it at the temperature of 2-8°C.

  DietDiethyl squarate is prepared by the reaction of dihydroxy-cyclobutenedione with ethanol . The reaction occurs in the solvent of benzene using the reagent of molecular sieves (3 Angstroem). The reaction time is 10 hours. The yield is about 89%.

  DietDiethyl squarate can be used to prepared other compounds such as 2,3-diethoxy-4-(2-furyl)-4-hydroxy-2-cyclobutenone , 3-ethoxy-4-(2-hydroxy-ethylamino)-cyclobut-3-ene-1,2-dione , dimethoxy-cyclobutenedione . For example,  DietDiethyl squarate reacts with furan-2-yl-lithium to give 2,3-diethoxy-4-(2-furyl)-4-hydroxy-2-cyclobutenone under the temperature of -78 ℃ using the solvent of tetrahydrofuran . The yield is about 79%.