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Advanced Organic Chemistry: H-1 NMR spectrum of 1-chlorobutane

The H-1 hydrogen-1 (proton) NMR spectrum of 1-chlorobutane

Doc Brown's Chemistry Advanced Level Pre-University Chemistry Revision Study Notes for UK IB KS5 A/AS GCE advanced A level organic chemistry students US K12 grade 11 grade 12 organic chemistry courses involving molecular spectroscopy analysing 1HNMR spectra of 1-chlorobutane

See also Comparing infrared, mass, 1H NMR & 13C NMR spectra of the 4 structural isomers of C4H9Cl

low and high resolution H-1 proton nmr spectrum of 1-chlorobutane analysis interpretation of chemical shifts ppm spin spin line splitting diagram n-butyl chloride doc brown's advanced organic chemistry revision notes

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 shifts, called chemical shifts, depend on the individual (electronic) chemical environment of the hydrogen atoms in an organic molecule, 1-chlorobutane here.

The chemical shifts quoted in ppm on the diagram of the H-1 NMR spectrum of 1-chlorobutane represent the peaks of the intensity of the chemical shifts (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 1-chlorobutane molecule.

 1-chlorobutane C4H9Cl, (c) doc b , (c) doc b

For more see Molecular structure, classification and naming of halogenoalkanes (haloalkanes)

Interpreting the H-1 NMR spectrum of 1-chlorobutane

For relatively simple molecules, the low resolution H-1 NMR spectrum of 1-chlorobutane is a good starting point - just blur the above 4 sets of chemical shift lines above - which clearly show that there 4 sets of protons in different chemical environments.

You can illustrate this with a coloured structural formula of 1-chlorobutane.

CH3CH2CH2CH2Cl  (this is the nearest I get to an art installation!)

(note the 4 colours indicating the 4 different chemical environment of the hydrogen atoms).

The proton ratio is 3 : 2 : 2 : 2 for the four different proton environments giving four principal and different chemical shift peaks.

As you can see, the high resolution spectrum of 1-chlorobutane is complex

The left-hand end CH3 is split by the adjacent CH2 into a 1 : 2 : 1 triplet at 0.92 ppm.

The right-hand end CH2 is split into a 1 : 2 : 1 triplet by the adjacent CH2 at 3.42.

All three sets of CH2 protons are split on both sides by adjacent non-equivalent protons into multiple resonance lines.

CH3CH2CH2CH2Cl

The 1.41 ppm chemical shift:

From the n+1 rule, the 'left-hand' CH2 protons (H2) are split by CH3 protons (H3) and by the middle CH2 protons (H2), (5 protons in total), into a 1:5:10:10:5:1 sextet of resonance lines.

This is pattern of resonances is a good indication of a propyl group (CH3CH2CH2).

The 1.68 ppm chemical shift:

The middle CH2 protons (H2) are split on both sides by CH2 protons (H2 and H2), (4 protons in total), into a 1:4:6:4:1 quintet of resonance lines.

Neither of these is clear on the on the H-1 NMR spectra of 1-chlorobutane shown above.


Number of protons 1H causing splitting Splitting pattern produced from the n+1 rule and the theoretical ratio of line intensities
0 means no splitting             1            
1 creates a doublet           1   1          
2 creates a triplet         1   2   1        
3 creates a quartet       1   3   3   1      
4 creates a quintet     1   4   6   4   1    
5 creates a sextet   1   5   10   10   5   1  
6 creates a septet 1   6   15   20   15   6   1
Comparing the infrared, mass, 1H NMR and 13C NMR spectra of the 4 halogenoalkane isomers of C4H9Cl

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-chlorobutane, 2-chlorobutane, 1-chloro-2-methylpropane and 2-chloro-2-methylpropane image sizes.  These four molecules are structural isomers of molecular formula C4H9Cl and exemplify the infrared, mass, 1H NMR and 13C NMR spectra of lower aliphatic halogenoalkanes (haloalkanes, alkyl halides, chloroalkanes, alkyl chlorides).

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. The infrared spectrum of 2-chloro-2-methylpropane is noticeably simpler in the fingerprint region, perhaps due to the greater symmetry of the molecule.

MASS SPECTRA (above): Theoretically, all four can give the parent molecular ions of m/z 92 and 94, but they are all relatively tiny peaks. 2-chlorobutane and 2-chloro-2-methylpropane give a base ion peak of m/z 57. The base ion peak for 1-chlorobutane is m/z 56 and that of 1-chloro-2-methylpropane is m/z 43. Each gives different patterns of pairs of m/z values two mass units apart, in the peak height ratio of 3:1, if the positive fragment contains a chlorine atom (35Cl or 37Cl) e.g look for m/z pairs 49/51, 63/65 and 77/79 in their mass spectra.

1H NMR SPECTRA (above): The 1H NMR spectra of all four molecules give different integrated proton ratios i.e.1-chlorobutane four peaks of ratio 3:2:2:2; 2-chlorobutane four peaks of ratio 3:3:2:1, 1-chloro-2-methylpropane three peaks of ratio 6:2:1 and 2-chloro-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-chlorobutane and 2-chlorobutane show four 13C NMR resonances, 1-chloro-2-methylpropane three 13C NMR resonances and 2-chloro-2-methylpropane only two 13C resonances (3 and 2 chemical environments respectively. Therefore 1-chloro-2-methylpropane and 2-chloro-2-methylpropane can be distinguished from the other three by their number of resonances in their 13C NMR spectra, but 1-chlorobutane and 2-chlorobutane cannot be distinguished from each other from their number of 13C NMR resonance lines - other data would be required.

Key words & phrases: Interpreting the proton H-1 NMR spectra of 1-chlorobutane, low resolution & high resolution proton nmr spectra of 1-chlorobutane, H-1 nmr spectrum of 1-chlorobutane, understanding the hydrogen-1 nmr spectrum of 1-chlorobutane, explaining the line splitting patterns in the high resolution H-1 nmr spectra of 1-chlorobutane, revising the H-1 nmr spectrum of 1-chlorobutane, proton nmr of 1-chlorobutane, ppm chemical shifts of the H-1 nmr spectrum of 1-chlorobutane, explaining and analyzing spin spin line splitting in the H-1 nmr spectrum, how to construct the diagram of the H-1 nmr spectrum of 1-chlorobutane, how to work out the number of chemically different protons in the structure of the 1-chlorobutane organic molecule, how to analyse the chemical shifts in the hydrogen-1 H-1 proton NMR spectrum of 1-chlorobutane

Molecular structure diagram of the proton NMR diagram for the 1H NMR spectrum of 1-chlorobutane. The proton ratio in the 1H NMR spectrum of 1-chlorobutane. Deducing the number of different chemical environments of the protons in the 1-chlorobutane molecule from the 1H chemical shifts in the hydrogen-1 NMR spectrum of 1-chlorobutane. Analysing the high resolution 1H NMR spectrum of 1-chlorobutane. Analysing the low resolution 1H NMR spectrum of 1-chlorobutane. You may need to know the relative molecular mass of 1-chlorobutane to deduce the molecular formula from the proton ratio of the 1H NMR spectrum of 1-chlorobutane. Revision notes on the proton NMR spectrum of 1-chlorobutane. Matching and deducing the structure of the 1-chlorobutane molecule from its hydrogen-1 NMR spectrum. Proton NMR spectroscopy of  aliphatic halogenoalkanes haloalkanes alkyl halides alkyl chlorides chloroalkanes, 1H NMR spectra of 1-chlorobutane, an isomer of molecular formula C4H9Cl


Associated links

The chemistry of HALOGENOALKANES (haloalkanes) revision notes INDEX

The infrared spectrum of 1-chlorobutane (n-butyl chloride)

The mass spectrum of 1-chlorobutane (n-butyl chloride)

The C-13 NMR spectrum of 1-chlorobutane (n-butyl chloride)

H-1 proton NMR spectroscopy index  (Please read 8 points at the top of the 1H NMR index page)

ALL SPECTROSCOPY INDEXES

All Advanced Organic Chemistry Notes

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