TMS is the acronym for tetramethylsilane, formula Si(CH₃)₄, whose protons are arbitrarily given a chemical shift of 0.0 ppm. This is the 'standard' in ¹H NMR spectroscopy and all other proton resonances, called chemical shifts, are measured with respect to the TMS, and depend on the individual (electronic) chemical environment of the hydrogen atoms in an organic molecule - 2-bromobutane here.

The chemical shifts quoted in ppm on the diagram of the H-1 NMR spectrum of 2-bromobutane represent the peaks of the intensity of the chemical shifts of (which are often groups of split lines at high resolution) AND the relative integrated areas under the peaks gives you the ratio of protons in the different chemical environments of the 2-bromobutane molecule.

Secondary haloalkane/halogenoalkane and old names: sec-butyl bromide, sec-butyl bromide (secondary alkyl halide)

Interpreting the H-1 NMR spectrum of 2-bromobutane

In terms of spin-spin coupling from the possible proton magnetic orientations, for 2-bromobutane I have only considered the interactions of non-equivalent protons on adjacent carbon atoms e.g. -CH₂-CH₃, and CH-CH₂-.

For relatively simple molecules, the low resolution H-1 NMR spectrum of 2-bromobutane is a good starting point (low resolution diagram above).

The 9 hydrogen atoms (protons) of 2-bromobutane occupy 4 different chemical environments so that the low resolution NMR spectra should show 4 principal resonance peaks of different H-1 NMR chemical shifts (diagram above for 2-bromobutane).

CH₃-CHBr-CH₂-CH₃

Note the proton ratio 3:1:2:3 of the 4 colours of the 9 protons of 2-bromobutane in the 4 chemically different proton environments

Chemical shifts (a) to (d) on the H-1 NMR spectrum diagram for 2-bromobutane.

Although there are 9 hydrogen atoms in the molecule, the proton NMR spectrum shows there are only 4 possible different chemical environments for the hydrogen atoms in 2-bromobutane molecule.

The integrated signal proton ratio 3:1:2:3 observed in the high resolution H-1 NMR spectrum, corresponds with the structural formula of 2-bromobutane.

The high resolution 1H NMR spectrum of 2-bromobutane

The high resolution spectra of 2-bromobutane shows 4 groups of proton resonances and in the 3:1:2:3 ratio expected from the structural formula of 2-bromobutane, but we can now consider the splitting of resonance lines from the spin-spin coupling in the molecule of 2-bromobutane.

The ppm quoted on the diagram represent the peak of resonance intensity for a particular proton group in the molecule of 2-bromobutane - since the peak' is at the apex of a band of H-1 NMR resonances due to spin - spin coupling field splitting effects - see high resolution notes on 2-bromobutane below.

So, using the chemical shifts and applying the n+1 rule to 2-bromobutane and make some predictions using some colour coding! (In problem solving you work the other way round!)

¹H NMR resonance (a) ¹H Chemical shift 1.70 ppm: CH₃-CHBr-CH₂-CH₃

This resonance is split into a 1:1 doublet by the adjacent CH proton (n+1 = 2).

Evidence for the presence of a CH group in the molecule of 2-bromobutane

¹H NMR resonance (b) ¹H Chemical shift 4.09 ppm: CH₃-CHBr-CH₂-CH₃

This resonance is split into a 1:5:10:10:5:1 sextet by the adjacent CH₃ and CH₂ protons on either side (n+1 = 6).

Evidence for the presence of a CH₃-CH_x-CH₂ grouping in the molecule of 2-bromobutane (x can be 2 or 1 as in this case for 2-bromobutane).

¹H NMR resonance (c) ¹H Chemical shift 1.83 ppm: CH₃-CHBr-CH₂-CH₃

This resonance is split into a 1:4:6:4:1 quintet by the adjacent CH and CH3 protons (n+1 = 5).

Evidence for the presence of a CH-CH_x-CH₃ grouping in the molecule of 2-bromobutane (x can be 1 or 2 as in the case for 2-bromobutane).

However - a very advanced footnote: 2-bromobutane is an asymmetric molecule and exhibits R/S isomerism (optical isomerism, mirror image enantiomers). This asymmetry actually affects the CH₂ protons field, and they actually have slightly different chemical shifts of 1.82 and 1.84. Since this is a pre-university website I have assumed they are equivalent and assigned them a chemical shift of 1.83 ppm as a compromise!

¹H NMR resonance (d) ¹H Chemical shift 1.03 ppm: CH₃-CHBr-CH₂-CH₃

This resonance is split into a 1:2:1 triplet by the adjacent CH₂ protons (n+1 = 3).

Evidence for the presence of a CH₂ group in the molecule of 2-bromobutane

Note the decreasing effect on the ¹H chemical shift as the proton is further from the more electronegative bromine atom 2-bromobutane.

Comparing the infrared, mass, 1H NMR and 13C NMR spectra of the 4 halogenoalkane isomers of C4H9Br NOTE: The images are linked to their original detailed spectral analysis pages AND can be doubled in size with touch screens to increase the definition to the original 1-bromobutane, 2-bromobutane, 1-bromo-2-methylpropane and 2-bromo-2-methylpropane image sizes.  These four molecules are structural isomers of molecular formula C4H9Br and exemplify the infrared, mass, 1H NMR and 13C NMR spectra of lower aliphatic halogenoalkanes (haloalkanes, alkyl halides, bromoalkanes, alkyl bromides).
INFRARED SPECTRA (above): Apart from the significant differences in the fingerprint region at wavenumbers 1500 to 400 cm-1, there are no other great striking differences, but each could be identified from its infrared spectrum.
MASS SPECTRA (above): All four give the parent molecular ions of m/z 136 and 138, but it is only a relatively tiny peak for 2-bromobutane and 2-bromo-2-methylpropane. All four give the base ion peak of m/z 57. All four give prominent peaks for m/z ions 27, 29, 39 and 41 and all give a tiny peak from an ionised iodine atom at m/z 127. They look quite similar to me and lack a clear fingerprint fragmentation pattern. There are small differences in the relative abundances (peak heights) for pairs of ions involving 79Br/81Br isotopes e.g. m/z 93/95, 107/109 and 121/123. 1-bromo-2-methylpropane is the only one of the four to have a prominent peak for the m/z 43 ion.
1H NMR SPECTRA (above): The 1H NMR spectra of all four molecules give different integrated proton ratios i.e.1-bromobutane four peaks of ratio 3:2:2:2; 2-bromobutane four peaks of ratio 3:3:2:1, 1-bromo-2-methylpropane three peaks of ratio 6:2:1 and 2-bromo-2-methylpropane gives just one peak '1' (effectively no ratio involved), so all four molecular structures can be distinguished from each other by their 1H NMR spectra proton ratios, numbers of peaks and (n+1) rule splitting patterns.
13C NMR SPECTRA (above): The 13C NMR spectra of the four molecules show various numbers of carbon-13 chemical environments i.e 1-bromobutane and 2-bromobutane show four 13C NMR resonances, 1-bromo-2-methylpropane three 13C NMR resonances and 2-bromo-2-methylpropane only two 13C resonances. Therefore 1-bromo-2-methylpropane and 2-bromo-2-methylpropane can be distinguished from the other three by their number of resonances in their 13C NMR spectra, but 1-bromobutane and 2-bromobutane cannot be distinguished from each other from their number of 13C NMR resonance lines - other data would be required.