Researcher

Cuepil Choi

Objective

To reinvestigate CRSEXP013 to see if acetals can be formed through simply heating 4-chlorobenzaldehyde and ethanol. A cleaner bottle of 4-chlorobenzaldehyde was used so that there were only trace amounts of 4-chlorobenzoic acid unlike in CRSEXP013.

Procedure

An excess amount of ethanol was added to 4-chlorobenzaldehyde in a 1 dram vial. The mixture was pipetted into an inner NMR tube and was examined at 55 C. After 3 hours, the NMR tube was taken out and another HNMR spectrum was taken the next day. All HNMR spectra were taken with D2O in outer coaxial insert NMR tube.

Results

HNMR 1 - (integration sheet) 15 minutes 25 C, D2O; 17:1 aldehyde to hemiacetal ratio
HNMR 2 - (integration sheet) 26 minutes 55 C, D2O; 18:1 aldehyde to hemiacetal ratio
HNMR 3 - (integration sheet) 36 min 55 C, D2O; 19:1 aldehyde to hemiacetal ratio
HNMR 4 (128 scan) - HNMR too distorted for accurate integrations; 56 min 55 C, D2O
HNMR 5 - (integration sheet) 61 min 55 C, D2O; 13:1 aldehyde to hemiacetal ratio
HNMR 6 - (integration sheet) 69 min 55 C, D2O; 16:1 aldehyde to hemiacetal 111:1 aldehyde to acetal ratios
HNMR 7 - (integration sheet) 90 min 55 C, D2O; 16:1 aldehyde to hemiacetal 25:1 aldehyde to acetal ratios
HNMR 8 - (integration sheet) 1295 min (overnight) 25 C, D2O; 7:1 aldehyde to hemiacetal 1.4:1 aldehyde to acetal ratios
CNMR 1 - 71 min 55 C, D2O

Discussion

It is unsure if reaction will go to completetion without driving off water. Experiment needs to be carried further to determine if it reaches an equilibrium before aldehyde is fully converted.

Conclusion

Acetals do seem to be formed with ethanol and 4-chlorobenzaldehyde. There was no peaks to suggest any of the 4-chlorobenzoic acid in t=0, meaning acetals can be created without any catalyst. Reaction continued overnight, reaching about 1:1 ratio between acetal and aldehyde.

Log

2013-09-03

15:18 0.0338 g of 4-chlorobenzaldehyde added to a 1 dram vial S-1
15:32 0.5734 g ethanol added to S-1
15:47 HNMR 1 taken at 25 C
15:50 NMR machine temperature set to 55 C
15:54 NMR machine temperature reaches 55 C
15:58 HNMR 2 taken at 55 C
16:08 HNMR 3 taken at 55 C
16:20-16:28 HNMR 4 taken at 55 C 128 scans
16:29 reacquired Z0, shim, and autolock because spectrum was going noisy. Z0 failed, NMR tube taken out and there were bubbles in D2O. NMR tube was tapped until bubbles disappeared, Z0, shim, auto lock reacquired again.
16:32 HNMR 5 taken at 55 C 8 scans
16:37-16:40 HNMR 6 taken at 55 C 64 scans
16:42 CNMR 1 taken with 256 scans
17:01 HNMR 7 taken at 55 C 8 scan

2013-09-04

13:06 HNMR 8 taken at 25 C