How many different NMR signals will be observed in the NMR spectrum of each of the following compounds theoretically? Determine the approximate chemical shift for each proton and highlight any diastereotopic relationships.

(i) 2-chlorobutane

(ii) methoxycyclopentane

The methyl-H highlighted in the isopentane structure appears at 0.87 ppm, while that of 2-methylbut-2-ene appears at 1.56 ppm. Rationalize this observation. 

Even though alkene hydrogens usually show up at similar chemical shifts between 5 and 6 ppm, the chemical shifts of the labeled alkene hydrogens below are different (H_a = 6.009 ppm; H_b = 7.034 ppm). Rationalize the difference.

Identify the labeled proton (or a set of protons) with the higher chemical shift.

Which statement explains why the methine proton has a higher chemical shift than the methyl proton?

Use the letters a, b, c, and so on to designate each set of chemically equivalent protons, starting with the lowest chemical shift in the 1H NMR spectrum. Include the multiplicity of each signal.

An NMR spectrum of an unknown compound obtained from a 400-MHz NMR spectrometer shows protons at a position 840 Hz downfield from the TMS.
(a) Determine the chemical shift of these protons.
(b) Determine their chemical shift in an 80-MHz NMR spectrometer.
(c) By how many Hz their chemical shift should be downfield from TMS using an 80-MHz NMR instrument?