CRSEXP031

=Researcher= Cuepil Choi =Objective= To determine the amount of hemiacetal formed from isopropyl alcohol and 4-chlorobenzaldehyde to investigate the role of steric hinderance in the hemiacetal formation. =Procedure= An excess amount of isopropyl alcohol was mixed with 4-chlorobenzaldhyde. The mixture was put in an inner coaxial insert NMR tube with CDCl3 in the outer tube. The sample was analyzed by HNMR spectroscopy after half an hour and two days. =Results= [|HNMR 1]: isopropyl alcohol and 4-chlorobenzaldehyde after approximately 30 minutes acetal: 6.15 ppm (1H, s) hemiacetal: 6.49 ppm (1H, s) [|Mole Fraction Spreadsheet]: Ratio of aldehyde to acetal is 63:1 and ratio of aldehyde to hemiacetal is 22:1. [|HNMR 2]: isopropyl and 4-chlorobenzaldehyde after two days [|HNMR 3]: isopropyl and 4-chlorobenzaldehyde after two days run with 64 scans acetal: 6.15 ppm (1H, s) hemiacetal: 6.49 ppm (1H, s) [|Mole Fraction Spreadsheet]: Ratio of aldehyde to acetal is 41:1 and ratio of aldehyde to hemiacetal is 11:1. =Discussion= It is incredibly surprising that this alcohol would form acetals so readily. We initially suspected that the isopropyl alcohol would actually not as readily form hemiacetals because of its steric hindrance, but after two days at room temperature the ratio of aldehyde to hemiacetal is 11:1, which is not too far off from ethanol's usual 9:1. The ratio of aldehyde to acetal at day two was 41:1. =Conclusion= A mixture of isopropyl alcohol and 4-chlorobenzaldehyde after two days at room temperature formed hemiacetal in a 11:1 ratio of aldehyde to hemiacetal and formed acetal in a 41:1 ratio of aldehyde to acetal.

2013-10-17
14:50 0.008 g of 4-chlorobenzaldehyde added to 1 dram vial S-1 14:52 0.95 g of isopropyl alcohol added to S-1 14:53 S-1 put into NMR sample 1 (sample placed in inner coaxial insert) 15:52 HNMR 1 taken of NMR sample 1. CDCl3 was used in an outer tube 10:49 HNMR 2 taken of NMR sample 1. CDCl3 was used in an outer tube 10:51 HNMR 3 taken of NMR sample 1 with 64 scans. CDCl3 was used in an outer tube