The CAS registry number of 2-Butynoic acid is 590-93-2. The IUPAC name is but-2-ynoic acid. Its EINECS registry number is 209-695-7. In addition, the molecular formula is C₄H₄O₂ and the molecular weight is 84.07. It is a kind of white to yellow powder and belongs to the classes of Acetylenes and Acetylenic Carboxylic Acids & Their Derivatives.

Physical properties about this chemical are: (1)ACD/LogP: 0.85; (2)ACD/LogD (pH 5.5): -2.01; (3)ACD/LogD (pH 7.4): -2.86; (4)ACD/BCF (pH 5.5): 1; (5)ACD/BCF (pH 7.4): 1; (6)ACD/KOC (pH 5.5): 1; (7)ACD/KOC (pH 7.4): 1; (8)#H bond acceptors: 2; (9)#H bond donors: 1; (10)#Freely Rotating Bonds: 0; (11)Polar Surface Area: 26.3 Å²; (12)Index of Refraction: 1.467; (13)Molar Refractivity: 20.15 cm³; (14)Molar Volume: 72.4 cm³; (15)Polarizability: 7.98 ×10^-24cm³; (16)Surface Tension: 48.4 dyne/cm; (17)Density: 1.159 g/cm³; (18)Flash Point: 90.9 °C; (19)Enthalpy of Vaporization: 48.41 kJ/mol; (20)Boiling Point: 203 °C at 760 mmHg; (21)Vapour Pressure: 0.117 mmHg at 25°C.

Preparation of 2-Butynoic acid: it can be prepared by ethynedicarboxylic acid and H₂O by heating to boiling. The equation as follows:

Uses of 2-Butynoic acid: it can be used to produce dibromocrotonylic acid, ethoxycrotonylic acid, ethyl butynoate, butynoyl chloride and butynamide. And it can react with pyridin-2-ylamine to get 2-Aminopyridine 2-butynoate. This reaction will need solvent acetone. The reaction time is 30 minutes. The yield is about 93%.

When you are using this chemical, please be cautious about it as the following:
This chemical can cause burns. And it is harmful by inhalation, in contact with skin and if swallowed.During using it, wear suitable protective clothing, gloves and eye/face protection. In case of contact with eyes, rinse immediately with plenty of water and seek medical advice. And in case of accident or if you feel unwell, seek medical advice immediately (show the label whenever possible.). In addition, you should take off all contaminated clothing immediately.

You can still convert the following datas into molecular structure:
(1)SMILES: O=C(C#CC)O
(2)InChI: InChI=1/C4H4O2/c1-2-3-4(5)6/h1H3,(H,5,6)
(3)InChIKey: LUEHNHVFDCZTGL-UHFFFAOYAN