CRSEXP036

=Researcher= Cuepil Choi =Objective= To prepare a preparatory yield of acetal from a mixture of 4-chlorobenzaldehyde and ethylene glycol by heating to 100°C. =Procedure= Prepared a mixture of 4-chlorobenzaldehyde (0.2g) and ethylene glycol (2g) in a screw cap test tube. This mixture was heated in a bath of boiling water for one hear and the mixture was analyzed by HNMR spectroscopy using the co-axial NMR tube system (the sample was in the inner insert and the CDCl3 reference was in the outer NMR tube). The mixture was allowed to stand overnight at room temperature, heated at 100C for an additional hour, and analyzed by HNMR spectroscopy using the co-axial NMR tube system. =Results= [|HNMR 1]: 4-chlorobenzaldehyde (bottle A #0941-0) dissolved in acetone to check the purity of the aldehyde. Pure with no traces of acid present. 4-chlorobenzaldehyde: 11.01 ppm (1H, s), 8.92 ppm (2H, m), 8.61 ppm (2H, m) acetone: 3.057 ppm (6H, s) [|HNMR 2]: 4-chlorobenzaldehyde in ethylene glycol after 1 hour of heating on day 1 4-chlorobenzaldehyde: 9.956 ppm (1H, s). ethylene glycol: 5.294 ppm (2H, s), 3.681 ppm (4H, s). acetal: 5.748 ppm (1H, s) hemiacetal: 5.638 ppm (1H, s) [|Mole Fraction Spreadsheet] [|HNMR 3]: 4-chlorobenzaldehyde in ethylene glycol after standing overnight at room temperature and an additional 1 hour of heating on day 2 4-chlorobenzaldehyde: 9.974 ppm (1H, s). ethylene glycol: 5.310 ppm (2H, s), 3.682 ppm (4H, s). acetal: 5.770 ppm (1H, s) hemiacetal: 5.670 ppm (1H, s) [|Mole Fraction Spreadsheet] =Discussion= After the initial heating on day 1, the mole fractions of 4-chlorobenzaldehyde, acetal, and hemiacetal were 0.018, 0.018, and 0.008. The ratio of aldehyde to acetal was 1:1 and ratio of aldehyde to hemiacetal was 2:1. After the heating on day 2, the mole fractions of 4-chlorobenzaldehyde, acetal, and hemiacetal were 0.004, 0.020, and 0.007. The ratio of aldehyde to acetal was 1:5 and ratio of aldehyde to hemiacetal was 1:2. The heating allowed a greater amount of acetal to be produced. =Conclusion= Heating the mixture of 4-chlorobenzaldehyde and ethylene glycol for 1 hour at 100C produced the acetal in a 1:1 aldehyde to acetal ratio. =Log=

2013-10-24
14:35 10 mL screw cap test tube 1 recorded mass of 9.8804 g without a cap 14:28 0.1957 g of 4-chlorobenzaldehyde put in test tube 1. aldehyde taken from bottle A (#0941-0) 15:24 small sample from bottle A dissolved in acetone and put in coaxial NMR tube 1 to check the purity. HNMR 1 taken. 15:30 1.9461 g of ethylene glycol added to test tube 1 15:35 ~80 mL of water added to a 100 mL beaker, hot plate temperature turned up to 135 C. Test tube 1 loosely capped. 16:14 raised temperature setting of hot plate to 215 C, not boiling. 16:16 raised temperature setting of hot plate to 230 C, not boiling 16:28 raised temperature setting of hot plate to 275 C, not boiling 17:14 raised temperature setting of hot plate to 370 C, bubbles in water, looked like very slow simmer 18:15 lowered temperature stetting of hot plate to 350, was boiling rapidly. 18:35 sample of oil at the bottom taken into inner NMR coaxial insert 2 18:45 HNMR 2 of sample taken 18:49 test tube 1 put out of bath, tightly sealed with cap.

2013-10-25
10:02 contents of NMR tube 2 put back into test tube 1. 10:04 capped lightly, put on heat plate with heat set to 300 C 10:30 temperature of hot plate set to 320 C. 11:30 test tube 1 taken out of bath. Mixture is clear 11:33 mixture is cloudy, 60 uL taken for NMR sample 3 in inner NMR coaxial insert. 11:34 test tube 1 placed in bath again 12:20 HNMR 3 of NMR sample 3 taken 12:22 test tube taken out of bath.