Advanced Organic Chemistry:13C NMR spectrum of 2-iodo-2-methylpropane (CH3)3CI

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Interpreting and explaining a 13C NMR spectrum: 2-iodo-2-methylpropane (tert-butyl iodide)

[Author © Dr Phil Brown PhD: Doc Brown's advanced level organic chemistry exam revision notes suitable for students of UK A level chemistry courses & US K12 grade 11, grade 12 and AP honors chemistry courses: Molecular spectroscopy analysis of 2-iodo-2-methylpropane (13C NMR spectra) [spectra page updated April 1st 2026 *]

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See also comparison of the infrared, mass, 1H NMR and 13C NMR spectra of the four isomers of C4H9I

Introductory note on the 13C NMR spectrum of 2-iodo-2-methylpropane

Students and teachers please note that my explanation of the carbon-13 NMR spectrum of 2-iodo-2-methylpropane is designed for advanced, but pre-university, chemistry courses.

The description does not involve the chemical shift δ spin-spin coupling effects for 2-iodo-2-methylpropane and the relative size of the carbon-13 NMR shifts does not give the ratio of the carbon atoms in the different non-equivalent chemical environments of the 2-iodo-2-methylpropane molecule.

The most common solvent used for investigating the 13C NMR spectrum of compounds like 2-iodo-2-methylpropane, is CDCl3 and other deuterated solvents.

13C nmr spectrum of 2-iodo-2-methylpropane (CH3)3CI analysis of chemical shifts ppm interpretation of C-13 chemical shifts ppm of tert-butyl iodide C13 carbon-13 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-iodo-2-methylpropane here.

2-iodo-2-methylpropane (tert-butyl iodide), C4H9I, (CH3)3C-I

The molecular structure and naming of haloalkanes

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

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

(CH3)3C-I

(Note the 2 different colours indicating the 2 different chemical environments of the 4 carbon atoms in 2-iodo-2-methylpropane).

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

(a)  (CH3)3C-I : 13C NMR chemical shift δ of 43.4 ppm for the methyl carbon atoms.

All three methyl carbon atoms are equivalent to each due to the symmetry of the 2-iodo-2-methylpropane molecule.

(b)  (CH3)3C-I : 13C NMR chemical shift δ of 40.4 ppm for the carbon atom bonded to the iodine atom.

The carbon-13 NMR spectra provides direct evidence of 2 different carbon atom environments for the 4 carbon atoms in the 2-iodo-2-methylpropane molecule, deduced from the presence of 2 different 13C NMR chemical shifts (ppm).
Comparing the infrared, mass, 1H NMR and 13C NMR spectra of the 4 halogenoalkane isomers of C4H9I

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-iodobutane, 2-iodobutane, 1-iodo-2-methylpropane and 2-iodo-2-methylpropane image sizes.  These four molecules are structural isomers of molecular formula C4H9I and exemplify the infrared, mass, 1H NMR and 13C NMR spectra of lower aliphatic halogenoalkanes (haloalkanes, alkyl halides, iodoalkanes, alkyl iodides).

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 ion of m/z 184, but it is only a relatively tiny peak for 2-iodo-2-methylpropane. All four give the base ion peak of m/z 57. All four give prominent peaks for m/z ions 29 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.

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

Key words & phrases: isomer of molecular formula (CH3)3CI Interpreting the C-13 NMR spectra of 2-iodo-2-methylpropane, 13C nmr spectrum of 2-iodo-2-methylpropane, understanding the carbon-13 nmr spectrum of 2-iodo-2-methylpropane, explaining the line pattern in the high resolution C-13 nmr spectra of 2-iodo-2-methylpropane, revising the C-13 nmr spectrum of 2-iodo-2-methylpropane, ppm chemical shifts of the C-13 nmr spectrum of 2-iodo-2-methylpropane, how to construct the diagram of the C-13 nmr spectrum of 2-iodo-2-methylpropane, how to analyse the chemical shifts in the carbon-13 NMR spectrum of 2-iodo-2-methylpropane deducing the chemical environment of all the carbon atoms in 2-iodo-2-methylpropane examining the c13 nmr spectrum of  2-iodo-2-methylpropane analysing the 13C nmr spectrum of 2-iodo-2-methylpropane how do you sketch and interpret the C-13 NMR spectrum of 2-iodo-2-methylpropane interpreting interpretation of the C-13 NMR spectrum of 2-iodo-2-methylpropane assignment of chemical shifts in the 13C NMR spectrum of 2-iodo-2-methylpropane type functional group  alkyl iodide haloalkane halogenoalkane tert-butyl iodide Molecular structure diagram of the carbon-13 NMR diagram for the 13C NMR spectrum of 2-iodo-2-methylpropane. Deducing the number of different chemical environments of the carbon atoms in the 2-iodo-2-methylpropane molecule from the 13C chemical shifts in the carbon-13 NMR spectrum of 2-iodo-2-methylpropane. Revision notes on the carbon-13 NMR spectrum of 2-iodo-2-methylpropane. Matching and deducing the structure of the 2-iodo-2-methylpropane molecule from its 13C NMR spectrum. Carbon-13 NMR spectroscopy of halogenoalkanes iodoalkanes, 13C NMR spectra of 2-iodo-2-methylpropane, an isomer of molecular formula C4H9I How do you interpret the chemical shifts of the C-13 NMR spectrum of 2-iodo-2-methylpropane How to interpret the C-13 NMR spectrum of 2-iodo-2-methylpropane Explanatory diagram of the 13C C-13 carbon-13 NMR spectrum of the  number of different carbon atom environments in the 2-iodo-2-methylpropane molecule from its carbon-13 NMR spectrum to help work out the molecular structure of the 2-iodo-2-methylpropane molecule? The uses and distinctive features of the carbon-13 NMR spectrum of the 2-iodo-2-methylpropane molecule explained. What do the number and values of the chemical shifts from the c-13 carbon-13 NMR spectrum tell us about the 2-iodo-2-methylpropane molecule? explaining the decoupled carbon-13 NMR spectrum of 2-iodo-2-methylpropane  with a detailed interpretation diagram of all the C-13 chemical shifts and intensities

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The chemistry of HALOGENOALKANES (haloalkanes) revision notes INDEX

The infrared spectrum of 2-iodo-2-methylpropane (tert-butyl iodide)

The mass spectrum of 2-iodo-2-methylpropane (tert-butyl iodide)

The H-1 NMR spectrum of 2-iodo-2-methylpropane (tert-butyl iodide)

C-13 NMR spectroscopy index

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Website content © Dr Phil Brown 2000+. All copyrights reserved on revision notes, images, quizzes, worksheets etc. Copying of Doc Brown's pre-university advanced level chemistry website material is NOT permitted. Exam revision summaries & references to science course specifications are unofficial. These organic chemistry revision notes on spectroscopy (on the 13C NMR spectrum of 2-iodo-2-methylpropane) are suitable for use of pre-university students studying AQA advanced level chemistry, Edexcel advanced level chemistry, OCR advanced level chemistry, IB advanced level chemistry, WJEC (Eduqas) advanced level chemistry, CIE advanced level chemistry, CCEA advanced level chemistry, US grade 11-12 AP honors chemistry courses and they will also prove useful to 1st year undergraduate students of chemistry.

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