Both questions please. frequescy 71. Dr. N. M. Arr was called in to help analyze

Question

Both questions please.

frequescy 71. Dr. N. M. Arr was called in to help analyze the 'H NMR spectrum of a mixture of compounds known to cootain only C, H and Br. The mixture showed two singlets-one at 1.8 ppm and the other at 2.7 ppm-with relative istegrabs of 1 :6, respectivel Dr Arr determined that the spectrum was that of a mixture of bromomethane and 2-bromo-2-methylpropane. What was ibe rali of bromomethane to 2-bromo-2-methylpropane in the mixture? 72. Calculate the amount of energy (in calories) required to flip an 'H nucleus in an NMR spectrometer that operates at 300 MH

Explanation / Answer

71. The singlet at 1.8 ppm corresponds to 9H's of 2-bromo-2-methylpropane.

The singlet at 2.7 ppm corresponds to 3H's of bromomethane.

According to the given data, the ratio of the singlet at 1.8 ppm to the singlet at 2.7 ppm = 1: 6

Therefore, the ratio of bromomethane to 2-bromo-2-methylpropane in the mixture = 1: 18

Explanation: The given ratio can be written as 1/2: 6/2 = 0.5: 3

The second term in the ratio, i.e. 3 corresponds to 100% because its actual value is 3.

And the first term, i.e. 0.5 corresponds to (0.5/9)*100 = (100/18)% because its actual value is 9.

i.e. The ratio = (100/18): 100

Multiply the ratio with 18/100 on both sides, you will get the ratio as 1: 18

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