1. How does the method of generating a Grignard reagent in this experiment diffe
ID: 948379 • Letter: 1
Question
1. How does the method of generating a Grignard reagent in this experiment differ from that which we performed in the first experiment of this semester? 2. Draw and label active nucleophile and electrophile in this reaction. Post-Lab Questions: 1. What gasses appear in the background spectra of an IR? Why doesn't N2 appear as well in the background IR spectrum even though it is the most abundant gas in the atmosphere? 2. Which of the following C-O stretches in IR will appear at the largest wavenumber? Which will be 2nd, and 3rd? Explain this trend. NH Can the following molecule be proved without a doubt by IR spectroscopy. If not what other spectroscopic methods could be used to prove the final product? How can this/these methods be used to nail down the exact structure? 3. OH 9Explanation / Answer
1. CO2 may appear in the background spectra of IR. N2 does not absorb infrared radiation.
2. Lets say the first molecule from left is 1, second is 2 and last one is 3.
3 will appear at highest wavenumber due to the electronegative effect of ester oxygen pulling electrons towards itself, thereby the lone pair on C=O oxygen is pulled towards the other oxygen. A greater double bond character is observed for C=O which abosrbs at highest wavenumber.
2 will appear second lower than ester carbonyl but higher than amide carbonyl. No such effect as seen in ester exists and thus comes at second wavenumber position.
Lastly, 1 will appear at lowest wavenumber, this is due to the lone pair on nitrogen is shifted towards N-C bond, making the C=O double bond less and more as C-O bond character. Thus absorbing at lower wavenumber.
3. The given molecule can be proved by Ir spectroschopy. Carboxylic acid -OH groups appear as very broad peak in the reion 2500-3400 cm-1. This can't be missed. The given structure thus must have a broad peak on this reagion to confirm this structure.
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