Chapter 3 Multiple Choice Questions

Fundamental constants

Planck's constant h = 6.626 10-34 J s
Boltzmann's constant kB = 1.381 10-23 J K-1
Vacuum permeability ?0 = 4? x 10-7 J s2 C-2 m-1
Gas constant R = 8.314 J K-1 mol-1

Magnetogyric ratios
Magnetogyric ratios of common nuclides can be found in Table 1.3, page 3.

. The 13C spectrum of a mixture of CHCl3 and CDCl3 comprises a doublet and a triplet. Each of the lines of the triplet is twice the intensity of each of the lines of the doublet. What is the proportion of CDCl3 in the mixture? [D = 2H]

. How many lines are there in the 2H spectrum of CD2H2? [D = 2H]

. PCl2F3 is trigonal bipyramidal (D3h symmetry). How many lines are there in the 19F spectrum when both chlorines are in (i) axial and (ii) equatorial positions?

. Which set of multiplets appears in the 1H spectrum of 2-chloro,2-methylbutane? Assume all three-bond JHH coupling constants are identical and ignore all other J-couplings.

. A 19F nucleus coupled to three protons has an NMR spectrum that comprises five equally spaced lines with relative intensities 1:2:2:2:1. One of the three JHF couplings is 10 Hz. What are the other two?

. A 1H multiplet comprises five equally spaced lines with relative intensities 1:2:3:2:1. It arises from a proton coupled to N equivalent nuclei with spin quantum number I. What are N and I?

. JHD, the H-D coupling constant in CHDCl2, is 27.2 Hz. What are JHH and JDD in (i) CH2Cl2 and (ii) CD2Cl2, respectively?

. Which of the following statements most accurately explains why the 1H spectrum of benzene is a singlet?

. The 60 MHz spectrum of a pair of strongly coupled protons has lines at the following positions relative to the centre of the spectrum: ±4.98 Hz and ±1.52 Hz. What is the J-coupling?

. A 13C atom and a 15N atom are 0.32 nm apart in a molecule. What is the 13C-15N dipolar splitting when the magnetic field is (i) parallel and (ii) perpendicular to the C-N vector?

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