exp018-a.jpg
(what was planned)
exp018-b.jpg
(what actually happened)

Researcher

Cuepil Choi

Objective

To see if a recrystallization of 4-chlorobenzaldehyde ethylene glycol acetal in cold ethanol is possible. MgSO4 was also tested to see if it was effective in removing ethylene glycol.

Procedure

4-chlorobenzaldehyde and ethylene glycol in a ratio of 1:1.5 were placed in a 25 mL erlenmeyer flask and left to reflux for 20 minutes. Crystals were drained in a sintered glass funnel with vacuum and cold ethanol was poured over it. The suctioned ethylene glycol from the sintered glass funnel was stored in a 5 dram vial and observed through NMR, GCMS, and TLC.

Results

HNMR 1 - 4-chlorobenzoic acid in acetone d6
HNMR 2 - stock bottle sample in acetone with D2O in outer tube
HNMR 3 - yellow layer of F-1
HNMR 4 - methylene chloride layer after separation
HNMR 5 - methylene chloride layer + MgSO4
HNMR 6 - ethylene glycol layer
HNMR 7- LM-3 taken on 2013-08-22

Discussion

This recrystallization may be a useful method of purifying aromatic aldehydes for older stock bottles that may have oxidized over time. The unusually large amount of 4-chlorobenzoic acid and ethylene present in GCMS may suggest that there may be a mechanism in the reaction that decomposed the acetal into the carboxylic acid and ethylene in the 250 C chamber.

Conclusion

This recrystallization produced 4-chlorobenzoic acid crystals rather than acetal crystals. It also prompted us to test for the acid in our stock bottles and several aromatic aldehyde bottles showed a good amount of carboxylic acid due to oxidation. The acetal product was in the ethylene glycol suction filtrate and the compound was confirmed my GCMS and NMR. The GCMS showed an unusually large quantity of 4-chlorobenzoic acid and a small trace of the acetal.

Log

2013-08-15

15:05 mass of 25 mL erlenmeyer flask 1 27.92 g
15:06 3.0395 g of 4-chlorobenzaldehyde added to flask 1
15:11 3.3541 g of ethylene glycol added to flask 1
15:12 hot plate set to 315 C
15:18 all crystals went into solution
15:19 approximately 1 drop every 3 seconds observed
15:20 hot plate temperature set to 325 C
15:23 hot plate temperature set to 320 C
15:40 hot plate temperature turned off
15:45 crystals started coming out, put in ice bath
15:50 slurry in flask 1 transferred to sintered glass funnel and vac turned on to remove ethylene glycol cork was used to press down crystals
15:55 ethylene glycol filtrate collected and put into 5 dram vial sample F-1
15:58 cold ethanol that was sitting in an icebath poured over crystals to wash. Ethanol filtrate collected in F-2
16:18 .0418 g of crystal put into chloroform, insolubility event
16:20 .0113 g of crystal put into acetone d6, product went in
16:43 HNMR 1 taken of product in acetone d6 at 25 C

2013-08-16

10:00 mass of 5 dram vial 1 11.8566 g
10:02 crystals in sintered glass funnel put into vial 1. Mass was 12.8341 g
10:03 mass of sintered glass funnel before washing with acetone was 33.896 g
10:05 sintered glass funnel washed with acetone, dried and weighed. Mass was 33.857 g.
11:00 HNMR 2 taken of 4-chlorobenzaldehyde stock bottle and acetone in an inner tube and D2O in an outer tube. HNMR taken at 25 C
11:10 HNMR 3 taken of yellow oil layer at the bottom of F-1 with D2O in an outer tube.
12:17 methylene chloride (approximately 1 mL) added to F-1 and shaken with a cap.
12:30 layers separated and both layers were taken into an NMR tubes
12:50 HNMR 4 taken of methylene chloride layer
13:23 MgSO4 added to yellow oil sample in NMR tube used for HNMR 2 to see if it would remove ethylene glycol
13:45 HNMR 5 taken of NMR tube with MgSO4
13:50 HNMR 6 taken of ethylene glycol layer

2013-08-20

10:46 F-1 has crystals are at the top. Two layers observed with top layer being clear and bottom being a yellow bubble. Crystals also noted on top of yellow bubble
10:54 carboxylic acid crystals retrieved from 2013-08-15 added to acetone in a 1 dram vial 1
10:59 sample from 4-chlorobenzaldehyde stock bottle put in 1 dram vial 2 and methylene chloride and acetone was added
11:09 crystals noted at the top of F-1 taken and mixed with methylene chloride in 1 dram vial 3. Not all crystals went in
11:15 bottom oil layer pipetted and put into 1 dram vial 4 along with acetone
11:17 bottom crystals and oil pipetted out and added methylene chloride in 1 dram vial 5
11:20 top layer taken without crystals and put into 1 dram vial 6 with acetone
11:32 top crystals from F-1 put in 1 dram vial 7 with acetone
11:46 TLC-1 ran with spots of vial 1, vial 2, vial 4, vial 5, vial 6, vial 7. Photo was taken
13:11 oil layer in F-1 taken and transfered to 1 dram vial named F-1.1

2013-08-21

11:45 acetone added to F-1.1
11:50 TLC-2 done with F-1.1 dotted in a straight line. Almost all of the 1 mL of F-1.1 was used
11:51 TLC-2 ran in methylene chloride
11:56 TLC-2 scraped in 4 locations (top, middle, middle, bottom) picture taken of scraped plate
11:58 top most layer scraped and put into pasteur pipette 1 with a kimwipe plug. 1.5 mL of methylene chloride was run through pipette 1. Filtrate labeled LM-1
12:01 1.5 mL of acetone run through the pipette 1 and collected in sample LA-1
12:19 upper middle layer scraped and put int pasteur pipette 2 with a kimwipe plug. 2 mL of methylene chloride was run through pipette 2. Filtrate labeled LM-2
12:20 2 mL of acetone run through the pipette 2 and collected in sample LA-2
12:29 lower middle layer scraped and put int pasteur pipette 3 with a kimwipe plug. 2 mL of methylene chloride was run through pipette 3. Filtrate labeled LM-3
12:30 2 mL of acetone run through the pipette 3 and collected in sample LA-3
12:32 bottom most layer scraped and put int pasteur pipette 4 with a kimwipe plug. 2 mL of methylene chloride was run through pipette 4. Filtrate labeled LM-4
12:35 2 mL of acetone run through the pipette 4 and collected in sample LA-4
14:00 LM-3 submitted for GCMS.
16:00 LM-3 was put into NMR tube

2013-08-22

14:00 HNMR 7 taken of LM-3