Question

Data

• amount of product collected = 1.727 g
• boiling range: 130–135 °C

%Transmittance 4000 1001 3500 3000 2958.30 2872.14 2500 Wavenumbers (cm-1) 2000 1739.12 1500 1465.49 1387 20 1366.34 1227.62 1171.02 1000 1055.05 1028.86 960.98 818.10 635.04 606.08 500 Dite: 10/24/1 Page 79

Questions:

1. Assign all signals in the diagnostic region (4000-1500 cm-1) and strong signals (less than 40% transmittance) in the fingerprint region (1500-500 cm-1). Create a spectral correlation table where each signal is assigned to a bond type or functional group. Discuss it in relation to the table you prepared for pre-lab assignment.
2. What would be the experimental evidence that alcohol or carboxylic acid were still present in the final sample (incomplete purification of the post-reaction mixture)?
3. The reaction is heated for about one hour but significant color change is not observed and it's quite difficult to tell if the reaction is done or not. Chromatography can be used to monitor the progress of the reaction. Which method, GC or TLC, would you use. Explain your choice.

Please answer and explain!

Answer 1

Here you didn't mentioned the starting materials but I guess the starting materials are butyric acid and isopropanol. Isopropyl butyrate has boiling point at 130-131 °C and you also mentioned the boiling point in this range.

IR list: 2985 and 2872 cm-1: C-H stretching, 1739: C=O, 1465: CH2 bending, 1387:CH3 bending, 1227: C-O stretching.

In order to check weather alcohol or carboxylic acid are present in the product one can check NMR and GC which will clearly give the information.

TLC is not a good idea to see these kind of aliphatic substrate which are not UV active compound (although you can use several TLC stain) but one can use gas chromatography to detect the unreacted alcohol or carboxylic acid. Each and every compound present in the product (as impurities) will show a seaparate signal in gas chromatography

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isopropyl butyrate