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Advanced Organic Chemistry: Carbon-13 NMR spectrum of 1-chlorobutane

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The Carbon-13 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 C-13 NMR spectra of 1-chlorobutane

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C-13 NMR spectroscopy - spectra index

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

C-13 nmr spectrum of 1-chlorobutane analysis of chemical shifts ppm interpretation of C-13 chemical shifts ppm of 1-chlorobutane n-butyl chloride doc brown's advanced organic chemistry revision notes 

TMS is the acronym for tetramethylsilane, formula Si(CH3)4, whose 13C atoms are arbitrarily given a chemical shift of 0.0 ppm. This is the 'standard' in 13C NMR spectroscopy and all other 13C shifts, called chemical shifts, depend on the individual (electronic) chemical environment of the 13C atoms in an organic molecule - 1-chlorobutane here.

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

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

Interpreting the C-13 NMR spectrum of 1-chlorobutane

You can see from the above there are four C-13 NMR chemical shift lines - which clearly show that the four carbon atoms of the 1-chlorobutane all in four 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 decreasing effect on the chemical shift as the carbon atom is further from the more electronegavtive electronegative chlorine atom of 1-chlorobutane.

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 C-13 NMR spectra of 1-chlorobutane, C-13 nmr spectrum of 1-chlorobutane, understanding the carbon-13 nmr spectrum of 1-chlorobutane, explaining the line pattern in the high resolution C-13 nmr spectra of 1-chlorobutane, revising the C-13 nmr spectrum of 1-chlorobutane, ppm chemical shifts of the C-13 nmr spectrum of 1-chlorobutane, how to construct the diagram of the C-13 nmr spectrum of 1-chlorobutane, how to analyse the chemical shifts in the carbon-13 NMR spectrum of 1-chlorobutane Molecular structure diagram of the carbon-13 NMR diagram for the 13C NMR spectrum of 1-chlorobutane. Deducing the number of different chemical environments of the carbon atoms in the 1-chlorobutane molecule from the 13C chemical shifts in the carbon-13 NMR spectrum of 1-chlorobutane. Revision notes on the carbon-13 NMR spectrum of 1-chlorobutane. Matching and deducing the structure of the 1-chlorobutane molecule from its 13C NMR spectrum. Carbon-13 NMR spectroscopy of  aliphatic halogenoalkanes haloalkanes alkyl halides alkyl chlorides chloroalkanes, 13C NMR spectra of 1-chlorobutane, an isomer of molecular formula C4H9Cl explaining the carbon-13 13C decoupled NMR spectrum of 1-chlorobutane

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 H-1 NMR spectrum of 1-chlorobutane (n-butyl chloride)

C-13 NMR spectroscopy index


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