If two signals in an NMR spectrum differ by 2.00 ppm in a 500-MHz spectrometer,
ID: 1054510 • Letter: I
Question
If two signals in an NMR spectrum differ by 2.00 ppm in a 500-MHz spectrometer, how do they differ in a 100-MHz spectrometer? Show your work for credit. How many^1H NMR signals would you expect from each of the following compounds. 1-bromobutane CH_2 = CHBr (CH_3)_2C = CH_2 2, 2, 3, 3-Tetrabromobutane The^1H NMR signal for a compound appears at 2000 Hz when recorded on a 200-MHz NMR spectrometer. What is the chemical shift for this proton? What would be the chemical shift in (a) ppm and (b)Hz, if the spectrum were recorded on a 500-MHz instrument?Explanation / Answer
NMR
1. If two signals in 500 MHz instrument differ by 2 ppm. Then on a 100 MHz instrument the different between te signals would be = (2 x 500)/100 = 10 ppm
2. Number of signals expected for,
a. 1-bromobutane = 4
b. CH2=CHBr = 2
c. (CH3)2C=CH2 = 2
d. 2,2,3,3-tetrabromobutane = 1
3. Signal appears at 2000 Hz on 200 MHz instrument
ppm shift value = 2000/200 = 10 ppm
If signal were recorded on a 500 MHz instrument instead,
(a) In ppm = 2000/500 = 4 ppm
(b) In Hz = 10 x 500 = 5000 Hz