CRSEXP030

=Researcher= Cuepil Choi =Objective= To see if reacting ethanol and 4-chlorobenzaldehyde to get acetals in a rotary evaporator would be a good preparatory method of making acetals. The ethanol would form an azeotrope with the water and would drive off the water as water formed from the creation of acetals. =Procedure= An excess of ethanol was mixed with 4-chlorobenzaldehyde in a 25 mL round flask. The round flask was put on a rotary evaporator with a weak vacuum. The rotating round flask was placed in a 60 C water bath until only crystals were left. Ethanol was added every time only crystals were left in the contents of the round flask. NMR samples were taken every time ethanol was added to the flask. CDCl3 was used in an outer NMR tube with the mixture in the inner coaxial insert. =Results= [|HNMR 1] - solution t=0, clean aldehyde with no carboxylic acid [|HNMR 2] - solution after being on the rotovap for about 15 minutes [|HNMR 3] - solution after being on the rotovap for about 30 minutes [|HNMR 4] - solution after being left alone overnight, in the NMR tube =Discussion= It is uncertain why the rotovap method would produce carboxylic acid rather than acetals. The prediction was that an ethanol water azeotrope would form, driving the equilibrium forward, favoring the acetal formation. =Conclusion= For some reason, the solution in the rotovap did not produce acetals as expected after 30 minutes of heating. Instead, the aldehyde was oxidized to carboxylic acid. The carboxylic peaks continued to grow until it was about 1:1 with the hemiacetal. HNMR 4 of the solution after sitting overnight, untouched, showed that acetals had started to form overnight. =Log=

2013-10-17
14:12 rotovap heat set to 65 C 14:13 25 mL round flask 1 mass recorded as 28.2289 g 14:16 0.1840 g of 4-chlorobenzaldehyde added to flask 1 (item number 0941-0) 14:20 1.4809 g of ethanol added to flask 1 14:21 swirled for approximately 30 s, all crystals went in 14:25 approximately 60 uL taken from flask 1 for NMR sample 1 (sample placed in inner coaxial insert) 15:01 flask 1 put on rotovap, vacuum turned on, bath temperature recorded at 65 C 15:15 only a film of crystals left in flask 1, rotovap turned off 15:16 flask 1 recorded mass of 28.3695 g 15:18 2.1880 g of ethanol added to flask 1. Contents swirled for 30 S, everything goes in 15:20 approximately 60 uL taken from flask 1 for NMR sample 3 (sample placed in inner coaxial insert) 15:29 HNMR 1 taken of NMR sample 1. CDCl3 was used in an outer tube 15:38 HNMR 2 taken of NMR sample 3. CDCl3 was used in an outer tube. 64 Scans done 16:38 rotovap bath recorded at 48 C, temperature control set to 65 C. flask 1 put on, rotovap turned on, vacuum applied, flask 1 lowered into bath. 16:53 only a film of crystals left in flask 1, rotovap turned off. Bath recorded to be at 65 C. 16:55 1.3500 g of ethanol added to flask 1 16:56 approximately 60 uL taken from flask 1 for NMR sample 3(sample placed in inner coaxial insert) 17:00 HNMR 4 taken of NMR sample 4. CDCl3 was used in an outer tube

2013-10-18
10:40 HNMR 5 taken of NMR sample 4. CDCl3 was used in an outer tube 11:01 HNMR 8 taken of ethanol used for whole experiment. CDCl3 was used in an outer tube