Questions relating to Sanders and Hunter Chapt 7
1. The 31P spectrum of phosphate changes as the pH of the solution is changed, because it changes what is in the solution. It can make the phosphate change from its anionic form to its cationic form which changes the spectra because it reflects the molecular structure.

2. The time scale of the instrument is what determines whether the signals are averaged or separate, if it is in slow exchange the signals are spate and if they are in fast exchange the signals are averaged.
3. A molecular complex with 2 conformations gives a pair of peaks on a 13C 200MHz spectrometer.
a. When the temperature of the sample was increased from 20 to 50 the pair of peaks changed to a single peak because the time scale changed. It changed from slow exchange (separate signals) to fast exchange that gave an averaged single …show more content…
Homonuclear decoupling experiment on a spin system Cha-CHb.
a. Selective irradiation of Hb decouples the nucleus from Ha, causing the Ha doublet to collapse into a singlet because, it only the Hb is irradiated at its own frequency making its exchange rate fast between the two spin states, this gives off an average signal. This means that the Ha is not split into a doublet by coupling with the two spin states it only couples with the averaged signal of the Hb so a single peak is achieved for both Ha and Hb.
b. To get a shaper peak for the Ha the decoupler power was increased as it needed to be increased as the difference between the RF and the resonance frequency of the Hb was large. The Hb frequencies power needed to be upped so that it could overcome the higher power of the RF so that its decoupling was stronger.

8. N-H’s may exchange quite slow, but being a quadrupolar nuclei, it spins (flip between spin states) fast meaning that it relaxes fast especially in non-symmetrical molecules like amides. This means that there is little time for it to exchange or couple with neighbouring H’s before the N-H has