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Advanced Organic Chemistry: C13 NMR spectra of E-but-2-ene & Z-but-2-ene

Interpreting the Carbon-13 NMR spectrum of E-but-2-ene and Z-but-2-ene

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 E-but-2-ene and Z-but-2-ene

13C nmr spectrum of E-but-2-ene C4H8 CH3CH=CHCH3 analysis of chemical shifts ppm interpretation of C-13 chemical shifts ppm of E-2-butene Z-2-butene trans-but-2-ene cis-but-2-ene trans-2-butene cis-2-butene C13 13-C nmr doc brown's advanced organic chemistry revision notes 

13C nmr spectrum of Z-but-2-ene C4H8 CH3CH=CHCH3 analysis of chemical shifts ppm interpretation of C-13 chemical shifts ppm of E-2-butene Z-2-butene trans-but-2-ene cis-but-2-ene trans-2-butene cis-2-butene 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 - E-but-2-ene and Z-but-2-ene here.

alkene alkenes structure and naming (c) doc b, structural formula of but-2-ene alkenes structure and naming (c) doc b , but doesn't show the two different spatial arrangements possible due to a high energy barrier to rotation about the double bond, known as the E/Z stereoisomers (cis/trans)

Interpreting the C-13 NMR spectrum of E-but-2-ene and Z-but-2-ene

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

CH3-CH=CH-CH3

(Note the 2 different colours indicating the 2 different chemical environments of the 4 carbon atoms in E-but-2-ene and Z-but-2-ene).

13C chemical shifts δ (a) to (b) on the C-13 NMR spectrum diagram for E-but-2-ene and Z-but-2-ene.

alkenes structure and naming (c) doc b  and  alkenes structure and naming (c) doc b

(a)  CH3-CH=CH-CH3 : 13C NMR chemical shift δ of 17 (E/trans) and 12 (Z/cis) ppm for the methyl carbon atoms.

In each isomer, both methyl carbon atoms are equivalent to each other because of the symmetry of both of the but-2-ene molecular isomers.

(b)  CH3-CH=CH-CH3 : 13C NMR chemical shift δ of 126 (E/trans) and 124 (Z/cis) ppm for the CH carbon atoms.

Again, in both isomers, the CH carbon atoms are equivalent to each other because of the symmetry of both of the but-2-ene molecular isomers.

For both isomers the pairs of 13C NMR resonances, albeit wide apart, are quite similar and note the much larger 13C chemical shift for the CH proton adjacent to the C=C double bond.

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


Key words & phrases: isomer of molecular formula C4H8 CH3CH=CHCH3 Interpreting the C-13 NMR spectra of E-but-2-ene and Z-but-2-ene, C-13 nmr spectrum of E-but-2-ene and Z-but-2-ene, understanding the carbon-13 nmr spectrum of E-but-2-ene and Z-but-2-ene, explaining the line pattern in the high resolution C-13 nmr spectra of E-but-2-ene and Z-but-2-ene, revising the C-13 nmr spectrum of E-but-2-ene and Z-but-2-ene, ppm chemical shifts of the C-13 nmr spectrum of E-but-2-ene and Z-but-2-ene, how to construct the diagram of the C-13 nmr spectrum of E-but-2-ene and Z-but-2-ene, how to analyse the chemical shifts in the carbon-13 NMR spectrum of E-but-2-ene and Z-but-2-ene deducing the chemical environment of all the carbon atoms in E-but-2-ene and Z-but-2-ene examining the c13 nmr spectrum of  E-but-2-ene and Z-but-2-ene analysing the 13-c nmr spectrum of E-but-2-ene and Z-but-2-ene how do you sketch and interpret the C-13 NMR spectrum of E-but-2-ene and Z-but-2-ene interpreting interpretation of the C-13 NMR spectrum of E-but-2-ene and Z-but-2-ene assignment of chemical shifts in the 13C NMR spectrum of E-but-2-ene and Z-but-2-ene functional group alkene cis-but-2-ene cis-2-butene trans-but-2-ene trans-2-butene

Molecular structure diagram of the carbon-13 NMR diagram for the 13C NMR spectrum of E-but-2-ene Z-but-2-ene trans-2-butene cis-2-butene. Deducing the number of different chemical environments of the carbon atoms in the E-but-2-ene Z-but-2-ene trans-2-butene cis-2-butene molecule from the 13C chemical shifts in the carbon-13 NMR spectrum of E-but-2-ene Z-but-2-ene trans-2-butene cis-2-butene. Revision notes on the carbon-13 NMR spectrum of E-but-2-ene Z-but-2-ene trans-2-butene cis-2-butene. Matching and deducing the structure of the E-but-2-ene Z-but-2-ene trans-2-butene cis-2-butene molecule from its 13C NMR spectrum. Carbon-13 NMR spectroscopy of alkenes, 13C NMR spectra of E-but-2-ene Z-but-2-ene trans-2-butene cis-2-butene, an isomer of molecular formula C4H8


Links associated with E-but-2-ene and Z-but-2-ene

The chemistry of ALKENES revision notes INDEX

The infrared spectra of the E/Z isomers of but-2-ene (cis/trans isomers of 2-butene)

The mass spectra of the E/Z isomers of but-2-ene (cis/trans isomers of 2-butene)

The H-1 NMR spectrum of E/Z but-2-ene (cis/trans isomers of 2-butene)

C-13 NMR spectroscopy index

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