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Chemspider links: 4-chlorobenzaldehyde ethylene glycol 4-chlorobenzaldehyde ethylene glycol hemiacetal 4-chlorobenzaldehyde ethylene glycol acetal

Researcher

Cuepil Choi

Objective

To examine whether ethylene glycol and 4-chlorobenzaldehyde would form an acetal and a hemiacetal without acetonitrile.

Procedure

1 Molar of 4-chlorobenzaldehyde and about 16 molars of ethylene glycol were mixed together in a vial. The mixture was heated with a heat gun in 5 second intervals until the 4-chlorobenzaldehyde dissolved in ethylene glycol. Mixture was put into NMR tube and a water bath was given to help the mixture reach the bottom of the tube. HNMR spectrum was taken at 55 C with deuterated water in an external tube.

Results

HNMR spectrum 1 - taken at 55 C (213 min) 1:15 ratio between acetal to aldehyde
HNMR spectrum 2 - taken at 25 C (1384 min) 1:5 ratio between acetal to aldehyde
HNMR spectrum 3 - taken at 55 C (1411 min) 1:3 ratio between acetal to aldehyde
HNMR spectrum 4 - taken at 55 C (1433 min) 1:2 ratio between acetal to aldehyde
HNMR spectrum 5 - taken at 26.4 C (1449 min) 1.6:1 ratio between acetal to aldehyde*
HNMR spectrum 6 - taken at 26.4 C (1458 min) 1:2 ratio between acetal to aldehyde*
*ratios may be largely inaccurate due to large amount of distortion

Discussion

The rise in ratio between acetal to aldehyde may suggests that the reaction may go to completion under reflux. The acetals also do not seem to be reversible since the acetal peaks do not diminish at room temperature.

Conclusion

The increase in ratio between acetal to aldehyde without any catalysts suggests that acetals can be created through simple heating. There is a 1:15 ratio between acetal to aldehyde after about 3 hrs. Multiplet peaks at 4-4.5ppm range are reasonable to expect from the mirror image CH2's in the acetal molecule. The rate of the reaction is impossible to decipher since the mixture was heated to a high temperature with a heat gun at first.

Log

2013-07-11

13:42 mass of empty 5-dram vial 1-E was 11.7658 g
13:43 0.4277 g of 4-chlorobenzaldehyde added to 1-E
13:47 1.5126 g of ethylene glycol added to 1-E
14:10 1-E heated up with heat gun 5 seconds at a time until all of the 4-chlorobenzaldehyde went in
14:13 pipetted mixture into inner coaxial insert NMR tube 1, but 4-chlorobenzaldehyde precipitated out, clogging the NMR tube
14:27 NMR tube 1 placed in warm water bath at 55 C to help solution reach the bottom of the tube
17:20 HNMR spectrum 1 taken of NMR tube 1 of solution 1-E at 55 C with outer tube containing deuterated water. deuterated water set to 4.8 ppm

2013-07-12

12:51 HNMR spectrum 2 taken at 26.1 C small bubble present at bottom of NMR tube. 4-chlorobenzaldehyde crystals are at the top of the tube. Deuterated water used in outer tube
13:18 HNMR spectrum 3 taken at 55 C
13:40 HNMR spectrum 4 taken again at 55 C.
13:56 HNMR spectrum 5 taken at 26.4 C
14:05 HNMR spectrum 6 taken at 26.4 C Air bubble at bottom was noted when NMR tube was taken out