CRSEXP037

=Researcher= Cuepil Choi =Objective= To obtain a preparatory yield of acetal from a mixture of piperonal and methanol by refluxing. =Procedure= A mixture of piperonal (0.5 g) and methanol was prepared in a test tube and refluxed for 1.5 hours. The content of the mixture was analyzed by HNMR after the refluxing using the co-axial NMR system with the sample in the coaxial insert and CDCl3 as the reference solvent in the outer NMR tube. =Results= [|HNMR 2]: Mixture after 1.5 hours of refluxing piperonal: 10.008 ppm (1H, s) methanol: 3.736 ppm (3H, t) acetal peak (possibly) at 5.54 ppm (1H, s). [|Mole Fraction Spreadsheet] =Discussion= The methanol had a mole fraction of 0.7907 and the piperonal had a mole fraction of 0.2056. The peak at 5.54 ppm may be the acetal peak, but it is unclear due to not having an HNMR spectra available from before the mixture was heated. If this peak is the acetal, it had a mole fraction of 0.0012 for a aldehyde to acetal ratio of 171:1. Surprisingly, the refluxing and heating of the mixture did not result in an increase in the amount of acetal formed. =Conclusion= Refluxing the piperonal and methanol mixture for 1.5 hours resulted in only a trace quantity of the acetal product. =Log=

2013-10-24
15:40 10 mL screw cap test tube 1 mass 9.8357 g 15:43 0.5039 g of piperonal taken from bottle #4910-4 put into test tube 1 15:44 2.2848 g of methanol added to test tube 1, piperonal goes in easily. 15:45 put in water bath with hot plate heat setting at 135 C 15:46 60 uL of mixture taken from test tube 1 and put in inner NMR coaxial insert tube 1 (CDCl3 in outer tube) 15:52 HNMR 1 taken of NMR tube 1 (t=0) 16:12 transferred contents of test tube 1 to 10 mL erlenmeyer flask 1 16:13 added 2.1980 g of methanol to have at least 1/3 of the erlenmeyer flask full. 16:14 temperature setting of hot plate raised to 215 C, flask 1 fitted with loose cap 16:15 flask 1 moved to different hot plate. Hot plate started cold, set to 200 C 16:28 flask 1 is at reflux, approximately 1 drop per second from the sides of the flask 16:35 more methanol added to flask 1 (~2 mL) 16:39 flask 1 back to reflux 17:02 more methanol added to flask 1 (~1.2 mL) 17:13 more methanol added to flask 1 (~3.5 mL), hot plate setting lowered to 175 C 18:15 60 uL of mixture taken from flask 1, put in inner NMR coaxial insert tube 2 (CDCl3 in outer tube) 18:45 HNMR 2 taken of NMR tube 2