Question

given the constant below, what is the absorption frequency in MHz in a 16.8 T field ofn19F and 31P? predict the appearence of the high resolution proton NMR spectrum of a)CH2CH2CN b)acetone c)toluene d)(CH3)3CCH2CHO

Answer 1

Absorption frequency,

Where,

B₀ = strength of the magnetic field = 16.8 T

= magnetogyric ratio

For ¹⁹F

Hence,

      = 672.874 MHz

For ³¹P

Hence,

      = 289.548 MHz

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a)

CH₃CH₂CN

The methyl group will appear as a triplet between 1 - 2 ppm.

The methylene group will appear as a quartet between 2 - 3 ppm.

b)

acetone : CH₃COCH₃

Both methyl group will appear as a singlet at 2.5 ppm as the molecule is symmetrical.

c)

toluene : C₆H₅CH₃

The protons in the phenyl ring will appear between 7 and 8 ppm as multiplets.

The methyl group will appear as a singlet between 2 - 3 ppm.

d)

(CH₃)₃CCH₂CHO

3 methyl groups of t-butyl moiety will appear as a singlet between 0.5 - 1.5 ppm.

Methylene group will appear as a singlet between 2 - 3 ppm.

The proton of -CHO group will appear as a singlet at 9 -10 ppm.