The 3-Butynoic acid, with the CAS registry number 2345-51-9, is also known as 2-Ethynylaceticacid. This chemical's molecular formula is C₄H₄O₂ and molecular weight is 84.07. What's more, its systematic name is but-3-ynoic acid.

Physical properties of 3-Butynoic acid are: (1)ACD/LogP: 0.09; (2)# of Rule of 5 Violations: 0; (3)ACD/BCF (pH 5.5): 1; (4)ACD/KOC (pH 5.5): 1; (5)#H bond acceptors: 2; (6)#H bond donors: 1; (7)#Freely Rotating Bonds: 1; (8)Polar Surface Area: 37.3 Å²; (9)Index of Refraction: 1.46; (10)Molar Refractivity: 19.973 cm³; (11)Molar Volume: 72.953 cm³; (12)Polarizability: 7.918×10^-24cm³; (13)Surface Tension: 48.059 dyne/cm; (14)Density: 1.152 g/cm³; (15)Flash Point: 82.592 °C; (16)Enthalpy of Vaporization: 47.523 kJ/mol; (17)Boiling Point: 194.939 °C at 760 mmHg; (18)Vapour Pressure: 0.186 mmHg at 25°C.

You can still convert the following datas into molecular structure:
(1)Canonical SMILES: C#CCC(=O)O
(2)InChI: InChI=1S/C4H4O2/c1-2-3-4(5)6/h1H,3H2,(H,5,6)
(3)InChIKey: KKAHGSQLSTUDAV-UHFFFAOYSA-N