Name Section:_ NMR Post-Lab #1 Determine which answer choice is the correct stru
ID: 554226 • Letter: N
Question
Name Section:_ NMR Post-Lab #1 Determine which answer choice is the correct structure from the NMR spectrum shown below: (4 pts) Please label which protons correspond the correct signal 1. A. 10.0 9.5 9.0 8.5 8.0 2. An NMR sample was ran on a 200 MHz NMR. The position of the signal for chloroform sho up at 1456 Hz. The standard for the NMR sample was TMS (tetramethylsiliane-0 Hz). Calculate the chemical shift of chloroform. (4pts) sition of signal position of TMS peak spectrometer frequency x 10 Chemical shift (8) You preformed the reaction shown below in lab. What would be the best spectroscopy method to determine which product was formed? (IR or NMR) Why? (4 pts) 3. KOH or ethanolExplanation / Answer
Q1)It is the spectrum of terephthaladehyde .
All the four aromatic protons are appearing as a singlet at 8.0 and both the aldehydic protons at 10.0 ppm.
option B
The other two structures have methyl groups whose peak must be at a lower ppm , around 4ppm in A and around 2.5 ppm in C.
Q2) position of signal = 1456
position of TMs = 0
frequecy used = 200MHz = 200x 106 Hz
Substituting the values in the given formula
chemical shift = [1456 - 0] x106 /200 x 106
= 7.28 ppm
Q3) NMR is the one which can be used to differentiate two products.
Product I is an exocyclic ompound with a signal corresponding the =CH2 at 4.6-4.8ppm
while that of product 2 which has the double bond inside the ring has a CH3 which no alpha H which would appear as singlet ar about 1.8 to 2.0 ppm.
Q4)
Aryl -H 7.2 ppm
aldhydic H at about 9.6 to 10.0 ppm
carboxylaicd H 9H of -COOH) appears between 10.0 to 13.0 ppm
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