IR can be used to know If a reaction is finished or not. One can monitor the pro

Question

IR can be used to know If a reaction is finished or not. One can monitor the progress of a reaction by comparing the peaks of the starting material with those of the products. We will be looking at the following reaction: On the following graph is a timeline of the I-R. You can see the spectrum of the reactant (the anhydride) for t = 0 min (the beginning of the reaction). Then you can see the spectrum of the product (Acetic acid)t = 30 min (the end of the reaction). Complete the graphs at t = 10 min and t = 20 min by drawing what you think the graph would look like.

Explanation / Answer

Following the reaction of acetic anhydride hydrolysis to acetic acid

At t = 0

we see C=O peaks (sharp) at 1790 cm-1 and 1840 cm-1 (approx) for the anhydride. No peaks in the 1750 cm-1 for C=O of carboxylic acid and no peak in 2500-3200 cm-1 region for O-H stretch.

at t = 10 min

we would see a small peak at 2500-3200 cm-1 (broad) for the O-H group and a peak at 1750 cm-1 for C=O stretch of the product appearing, along with C=O peaks (sharp) at 1790 cm-1 and 1840 cm-1 (approx) for the anhydride.

at t = 20 min

we would see a large peak at 2500-3200 cm-1 (broad) for the O-H group and a peak at 1750 cm-1 for C=O stretch of the product appearing, along with small C=O peaks (sharp) at 1790 cm-1 and 1840 cm-1 (approx) for the anhydride.

at t = 30 min

we see a broad peak at 2500-3200 cm-1 for O-H stretch of carboxylic acid group, 1750 cm-1 (broad) for C=O of carboxylic acid.

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