BioPHYSICAL chemistry

16.2

16.3

16.4 Large chemical shifts usually arise from small shielding and low

electron density.

16.5 Large chemical shifts usually arise from small shielding and low

electron density. The shielding constant is a measure of the extent

of the shielding.

16.6 The separation of the spectra improves with increasing frequency.

16.7 For two spins Aand Bcoupled by J, the lowest energy state is:

16.8 There are n+ 1 =5 lines.

16.9 An inhomogeneous field that increases in strength across the sample.

16.10 The spins will flip along the direction of the field of the spin pulse

and then decay back to the direction along the external field with

a time constant T 2.

16.11I=1 so there are three lines.

16.12I=1/2 so there are two lines.

16.13 Chemical shift Split by

CαH4.52 CβH 2

CβH 2 2.15 and 2.01 CαH and CγH 2

CγH 2 2.64 and 2.64 CβH 2

CεH 3 2.13

16.14The spectrum should have six diagonal peaks and five off-diagonal

peaks.

16.15 By the proper combination of pulses, the spins will realign after being

flipped, creating a large NMR signal termed an echo.

16.16 In a homogeneous field, a single peak is observed, reflecting the

resonance frequency of the water. For an inhomogeneous field,

three peaks are present at the relative locations of the beakers.

Eh h hJ=− AB− +

1

2

1

2

1

4

99

μnew

pnew

e

m

(. )(.

==

Z ××−−

2

16 10^19 C105 10^334

29

25 1

24 10

205 10

Js

kg

JT

)

()

.

×

− =×−−

ν

γ

ππ

==(. ×−−) ( )× =

B

2

1

2

193 10^711 Ts 9 T. 2 ..76 10×=^71 sMHz− 27 6

ν

γ

ππ

==(. ×−−) (×)=

B

2

1

2

193 10^711 Ts 20 T 66 1 10..×=^61 sMHz− 61 3

ANSWERS TO PROBLEMS 477

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