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Chemspider links: 4-nitrobenzaldehyde ethylene glycol 4-nitrobenzaldehyde ethylene glycol acetal

Researcher

Cuepil Choi

Objective

To see if 4-nitrobenzaldehyde would produce 4-nitrobenzaldehyde ethylene glycol crystals that were not oils at room temperature. The trouble extracting the acetal product because of its oil form from CRSEXP010 prompted this experiment.

Procedure

Acetals were produced through refluxing 0.5 g of 4-nitrobenzaldehyde in 23 g of ethylene glycol in a 50 mL erlenmeyer flask with a loose cap at 180 C for approximately 1 hour. Mixture was placed in a refrigerator overnight. Mixture was placed into a 30 mL seperatory funnel and benzene was added. Top layer of benzene and acetals were taken after a thorough shaking of the mixture. Possible amounts of ethylene glycol and water were removed by adding magnesium sulfate. Magnesium sulfate was removed through filtering the mixture through a pipette with a kimtech plug. HNMR spectra were taken of mixture prior to being cooled down and after the final benzene acetal mixture was produced. NMR tubes were placed in a bigger NMR tube containing deuterated water.

Results

All spectra were taken in a 500 mHz NMR and have deuterated water centered at 4.8 ppm
HNMR 1 - 4-nitrobenzaldehyde ethylene glycol after approximately 30 minutes of reflux - no aldehyde detected (couldn't find CHO peak), doublets assumed to be hemiacetals because of peaks that looked like benzylic peaks.
HNMR 2 - final acetal benzene mixture - pure acetal in benzene
HNMR 3 - W1.1 with CDCl3 - pure acetal in CDCl3
CNMR 1 of W1.1 with CDCl3

Discussion

This method of separating acetals from an impure ethylene glycol acetal mixture may be viable for 4-chlorobenzaldehyde. Absence of hemiacetals from the benzene layer may mean that hemiacetals were stuck in the ethylene glycol layer and may even be isolatable. The absence of ethylene glycol in the HNMR spectrum 2 suggests that magnesium sulfate may be able to remove ethylene glycol from a benzene solution.

Conclusion

Crystals were retrieved after benzene evaporated. The crystals were tested in CDCl3 as well. HNMR 1 contained two doublet peaks that seem to point towards hemiacetals. No carboxylic peaks we expect to find on 4-nitrobenzaldehyde was present, but peaks that usually indicated hemiacetal benzylic peaks were found.

Log

2013-07-25

10:02 mass of erlenmeyer flask 40.5521 g
10:03 0.5532 g 4-nitrobenzaldehyde added to flask 1
10:04 23.1987 g ethylene glycol added to flask 1
10:09 sample R-1 taken at t=0 at 25 C after stirring with stirring bar at 170 rpm
10:11 hot plate set to 340 C
10:16 mixture became clear temperature at 110 C sample R-2 taken
10:25 sample R-3 taken at 160 C
10:26 hot plate temperature raised to 390 C
10:27 hot plate temperature lowered to 310 C small bubbles at bottom noted as mixture comes close to simmer. Approximately 1 drop per second noted, mixture deemed to be at reflux.
10:28 sample R-4 taken at 182 C
10:30 hot plate raised to 250 C because simmer has disappeared
10:32 small bubbles appearing again
10:44 temperature lowered to 300 C
10:51 temperature raised to 350 C
10:55 temperature lowered to 325 C sample R-5 taken
11:07 sample R-5 placed into ice
11:09 sample R-5 taken out of ice bath
11:20 sample R-5 filtered through kimtech pasteur pipette filter. Filtrate placed in NMR tube
11:27 HNMR spectrum 1 taken at 26.1 C with outer NMR tube with deuterated water. deuterated water peak set to 4.8
11:30 flask taken off of hot plate
11:35 small sample taken in a 5 dram vial, cooled in ice bath and filtered through sintered glass funnel. Paste stored in 1 dram vial. Filtrate stored in 1 dram vial as well.

2013-07-26

14:22 mixture in flask 1 and 5 mL benzene placed in 50 mL separatory funnel
14:24 seperatory funnel shaken several times to release potential gas buildup
14:25 bottom layer of ethylene glycol taken out and discarded
14:27 Magnesium sulfate added to benzene acetal mixture W-1 until magnesium sulfate stopped coagulating
14:30 filtered through pasteur pipette with kimtech filter W-1.1
15:07 HNMR spectrum 2 of acetal benzene mixture W-1.1 taken
15:20 samples were left open to dry and crystalize

2013-08-30

12:34 W-1.1 dry sample with supposed acetals put into melting point apparatus. Melting point recorded at 86 C
13:00 CDCl3 added to W-1.1 and put into NMR tube.
13:10 HNMR 3 taken of W-1.1 with CDCl3 at 25 C
13:20 CNMR 1 taken of W-1.1 with CDCl3 at 25 C