crsexp007scheme.jpg
Chemspider links: 4-chlorobenzaldehyde ethanol 4-chlorobenzaldehyde ethanol acetal 4-chlorobenzaldehyde ethanol hemiacetal

Researcher

Cuepil Choi

Objective

To examine whether ethanol and 4-chlorobenzaldehyde would form acetals after heating.

Procedure

Approximately 0.1 g of 4-chlorobenzaldehyde and and 1.4 g of ethanol were mixed together in a 5-dram non screwcap vial 1-E and tritrurated several times to dissolve the 4-chlorobenzaldehyde. The mixture was then pipetted into an inner coaxial insert NMR tube 1 with outer coaxial insert tube containing deuterated water. NMR tube 1 was heated in the NMR machine to 60 C for about 30 min on the first day. A new mixture of similar ratios was mixed in vial 2-E and placed in inner coaxial insert NMR tube 2. NMR tube 2 was heated in a water bath for approximately 50 minutes then for about 10 minutes in the NMR machine. All NMR spectra were taken in a 500 mHz machine

Results

HNMR spectrum 1 - taken at 25.8 C (23 min) no acetal, 1:13 ratio between hemiacetal to aldehyde
HNMR spectrum 2 - taken at 60 C (37 min) no acetal, 1:9 ratio between hemiacetal to aldehyde
HNMR spectrum 3 - taken at 60 C (47 min) no acetal, 1:18 ratio between hemiacetal to aldehyde
HNMR spectrum 4 - taken at 60 C (67 min) no acetal, 1:23 ratio between hemiacetal to aldehyde
HNMR spectrum 5 - taken at 26.3 C (77 min) no acetal 1:15 ratio between hemiacetal to aldehyde
HNMR spectrum 6 - taken after approximately 1 hr 30 min bath at 70 C (1312 min) 1:20 ratio between hemiacetal to aldehyde

Discussion

The absence of acetal may be because the reaction is too slow at 60 C. CRSEXP006 may have been successful at creating acetals because the heat gun would have raised the mixture's temperature much higher than 60 C.

Conclusion

HNMR spectra show no acetal despite 30 minutes of heating at 60 C in the NMR machine. The reason for fluctuations in hemiacetal to aldehyde ratio is unknown, the integrations were done through google appscripts. Manual integrations show that the ratio is fairly equal in all spectra.

Log

2013-07-15

13:54 mass of empty 5-dram non screwcap vial 1-E was 11.8009 g
13:55 0.1125 g 4-chlorobenzaldehyde added to 1-E
13:58 1.4671 g of ethanol added to1-E
13:59 mixture triturated several times to dissolve 4-chlorobenzaldehyde
14:00 pipetted into inner coaxial insert NMR tube 1
14:05 NMR tube 1 inserted into outer coaxial insert NMR tube with deuterated water
14:21 HNMR spectrum 1 taken at 25.8 C
14:31 temperature of NMR machine set to 60 C
14:35 temperature of NMR machine reached 60 C
14:35 HNMR spectrum 2 taken at 60 C
14:45 HNMR spectrum 3 taken at 60 C
15:05 HNMR spectrum 4 taken at 60 C
15:10 temperature taken down to 25 C
15:15 temperature down to 25 C
15:15 HNMR spectrum 5 taken at 26.3 C

2013-07-16

10:35 mass of empty 5-dram vial 2-E 11.7993 g
10:36 0.1238 g of 4-chlorobenaldehyde added to 2-E
10:38 1.4175 g of ethanol added to 2-E
10:39 mixture triturated several times to dissolve 4-chlorobenzaldehyde
10:42 mixture pipetted into inner coaxial insert NMR tube 2 and capped
10:46 NMR tube 2 put into water bath at 70 C (approx 10 cm of tube was above water)
11:35 NMR tube 2 taken out of water bath
11:36 NMR tube 2 placed in outer coaxial insert tube with deuterated water
11:44 NMR tube 2 into NMR machine at 26.3 C
11:48 NMR reaches 69 C
11:50 HNMR 6 taken at 69 C deuterated water set to 4.8 ppm