Synthesis of 3-butynoic acid

3-Butynoic acid was synthesized following a previously reported procedure³⁶, with modification. Deionized water (135 mL) was added to a 500 mL single neck round bottom flask fitted with magnetic stirrer bar. Seventy percent HNO₃ (0.170 mL, 0.05 eq., 2.5 mmol), Na₂Cr₂O₇ · 2H₂O (0.15 g, 0.01 eq., 0.5 mmol), and NaIO₄ (34.2 g, 3.2 eq., 160 mmol) were subsequently added to the flask and the mixture was stirred vigorously on an ice bath for 15 min. 3-Butyn-1-ol (3.50 g, 1 eq., 50 mmol) was diluted with chilled deionized water (135 mL), added to the flask slowly, and stirred overnight. After this time, the reaction mixture was filtered to remove insoluble salts, and the product was extracted from the aqueous phase using diethyl ether (80 mL × 5). The organic fractions were combined, dried over anhydrous magnesium sulfate, and concentrated under rotary evaporation to give an orange viscous liquid. Subsequent washing with pentane (200 mL × 3) and further concentration under rotary evaporation times yielded 3-butynoic acid as an off-white solid (2.19 g, 52% yield). ¹H NMR (500 MHz, Chloroform-d) δ (ppm) 3.38 (d, 2H, J = 2.7 Hz), 2.25 (t, 1H, J = 2.7 Hz); ¹³C NMR (125 MHz, Chloroform-d) δ (ppm) 173.8, 74.8, 72.4, 25.6.