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Advanced Organic Chemistry: Carbon-13 NMR spectrum of 2-chloro-2-methylpropane

The Carbon-13 NMR spectrum of 2-chloro-2-methylpropane

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 2-chloro-2-methylpropane

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

C4H9Cl (CH3)3CCl C-13 nmr spectrum of 2-chloro-2-methylpropane analysis of chemical shifts ppm interpretation of 13C chemical shifts ppm of tert-butyl chloride C13 13-C nmr 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 resonances, called chemical shifts, are measured with respect to the TMS, and depend on the individual (electronic) chemical environment of the 13C atoms in an organic molecule - 2-chloro-2-methylpropane here.

(c) doc b, (c) doc b, (c) doc b, (c) doc b, 2-chloro-2-methylpropane

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

Interpreting the C-13 NMR spectrum of 2-chloro-2-methylpropane

As you can see from the diagram above there are 2 different chemical shift lines in the C-13 NMR spectrum of 2-chloro-2-methylpropane indicating 2 different chemical environments of the 4 carbon atoms of 2-chloro-2-methylpropane.

(CH3)3CCl

(Note the 2 different colours indicating the 2 different chemical environments of the carbon atoms in 2-chloro-2-methylpropane).

13C chemical shifts (a) to (b) on the C-13 NMR spectrum diagram for 2-chloro-2-methylpropane.

The three methyl group carbon atoms are all equivalent in 2-chloro-2-methylpropane.

The carbon-13 NMR spectra provides direct evidence of 2 different carbon atom environments for the 4 carbon atoms in the 2-chloro-2-methylpropane molecule, deduced from the presence of 2 different 13C chemical shifts (ppm).

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: C4H9Cl (CH3)3CCl Interpreting the C-13 NMR spectra of 2-chloro-2-methylpropane, C-13 nmr spectrum of 2-chloro-2-methylpropane, understanding the carbon-13 nmr spectrum of 2-chloro-2-methylpropane, explaining the line pattern in the high resolution C-13 nmr spectra of 2-chloro-2-methylpropane, revising the C-13 nmr spectrum of 2-chloro-2-methylpropane, ppm chemical shifts of the C-13 nmr spectrum of 2-chloro-2-methylpropane, how to construct the diagram of the C-13 nmr spectrum of 2-chloro-2-methylpropane, how to analyse the chemical shifts in the carbon-13 NMR spectrum of 2-chloro-2-methylpropane deducing the chemical environment of all the carbon atoms in 2-chloro-2-methylpropane examining the c13 nmr spectrum of  2-chloro-2-methylpropane analysing the 13-c nmr spectrum of 2-chloro-2-methylpropane how do you sketch and interpret the C-13 NMR spectrum of 2-chloro-2-methylpropane interpreting interpretation of the C-13 NMR spectrum of 2-chloro-2-methylpropane assignment of chemical shifts in the 13C NMR spectrum of tert-butyl chloride

Molecular structure diagram of the carbon-13 NMR diagram for the 13C NMR spectrum of 2-chloro-2-methylpropane. Deducing the number of different chemical environments of the carbon atoms in the 2-chloro-2-methylpropane molecule from the 13C chemical shifts in the carbon-13 NMR spectrum of 2-chloro-2-methylpropane. Revision notes on the carbon-13 NMR spectrum of 2-chloro-2-methylpropane. Matching and deducing the structure of the 2-chloro-2-methylpropane molecule from its 13C NMR spectrum. Carbon-13 NMR spectroscopy of  aliphatic halogenoalkanes haloalkanes alkyl halides alkyl chlorides chloroalkanes, 13C NMR spectra of 2-chloro-2-methylpropane, an isomer of molecular formula C4H9Cl


Links associated with 2-chloro-2-methylpropane

The chemistry of HALOGENOALKANES (haloalkanes) revision notes INDEX

The infrared spectrum of 2-chloro-2-methylpropane (tert-butyl chloride)

The mass spectrum of 2-chloro-2-methylpropane (tert-butyl chloride)

The H-1 NMR spectrum of 2-chloro-2-methylpropane (tert-butyl chloride)

C-13 NMR spectroscopy index

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