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Researcher

Cuepil Choi

Objective

To see if heating ethanol and 4-chlorobenzaldehyde would produce acetals like CRSEXP006 with 4-chlorobenzaldehyde and ethylene glycol.

Procedure

Approximately 1 gram of 4-chlorobenzaldehyde was put in a 50 mL erlenmeyer flask with about 20 mL of ethanol. Sample was refluxed for 4 hours. Sample was boiled at a high temperature after 4 hours to see if higher temperatures would affect the solution differently.

Results

HNMR spectrum 1 - R-6
HNMR spectrum 2 - R-7
HNMR spectrum 3 - R-1
HNMR spectrum 4 - R-9

Discussion

The fact that the 4-chlorobenzaldehyde to hemiacetal ratio started out as 1:3 and changed to 2:1 despite taking the NMR at 25 C gives contradictory results to previous ethanol and 4-chlorobenzaldehyde experiments such as CRSEXP001 since it suggests a slow equilibrium. A slow equilibrium would mean that the hemiacetal may be isolatable.

Conclusion

No acetals were detected. 4-chlorobenzoic acid was discovered within the HNMR's, suggesting that the contents of the 4-chlorobenzaldehyde bottle had oxidized. HNMR spectra of R-6, R-7, and R-9 had almost a 1:2 ratio between 4-chlorobenaldehyde and the hemiacetal. R-1 had a ratio of 1:3 between the 4-chlorobenzaldehyde and hemiacetal.

Log

2013-07-31

10:37 mass of 50 mL erlenmeyer flask 1 40.5519 g
10:40 new bottle of 4-chlorobenzaldehyde used, some crystals on top are noted to be a more yellowish color than the white noted from the previous bottle and under the upper layer of crystals. Possibly carboxylic acid.
10:40 1.3501 g of 4-chlorobenzaldehyde added to flask 1
10:42 20.5362 g of ethanol added to flask 1
10:49 stirring bar added to flask 1 and stirred at 150 rpm
11:00 all crystals have dissolved, sample R-1 obtained
11:00 hot plate settings set to 180 rpm and 200 C
11:10 sample R-2 obtained, was boiling at this point in time. Hot plate setting lowered to 130 C
11:20 sample R-3 obtained at 69 C (obtained with temperature gun pointed at stirring bar), was no boiling at this point in time. Hot plate setting raised to 180 C
11:25 temperature of solution at 85 C hot plate lowered to 120 C
11:37 slow simmer achieved, solution at 103 C. Sample R-4 obtained
12:00 sample R-5 obtained
12:12 sample R-6 obtained at 105 C
12:24 HNMR spectrum 1 taken of R-6
13:10 sample R-7 obtained at 108 C
13:45 HNMR spectrum 2 taken of R-7
13:49 HNMR spectrum 3 of R-1 obtained
13:52 erlenmeyer flask 1 taken off of hot plate, sample R-8 taken
13:54 erlenmeyer flask 1 put on hot plate again, temperature raised to 250 C
13:58 hot plate raised to 300 C
14:08 sample R-9 obtained, most of liquid had boiled off
14:16 HNMR spectrum 4 taken of R-9