NOESY NMR Spectrum gHMQC NMR Spectrum Figure 1 Figure 4...

Cinnamaldehyde is theprimary organic moleculethat gives cinnamon itscharacteristic scent and zest.This compound iscomposed of amonosubstituted benzenering, a trans-alkene, and analdehyde functional group.

The molecular formula and molecular weight ofcinnamaldehyde is C9H8O and 132.16g/mol, respectively.The structure of cinnamaldehyde is shown in Figure 1.

1H 1D NMR Spectrum

appearing at9.73 ppm.The chemicalshift of HA isindicative ofthe aldehydeproton at C1.Figure 3 is anexpandedview of thearomatic andalkene region

gHMQC NMR Spectrum

13C 1D NMR SpectrumThe 13C spectrum ofcinnamaldehyde isshown in Figure 6.The spectrum wasrecorded at 500MHz (1H) with a aspectral width of28409.1 Hz.Resonance CA, themost downfieldresonance, belongsto C1, the carbonylcarbon. The threepeaks at 77.3 belongto the solvent,CDCl3. Figure 7represents thearomatic regionbetween 127 ppmand 153 ppm. Thisalso includes thealkene carbons thatare part of theconjugated system.

ReferencesHanHong. Trans-Cinnamaldehyde. Web. 20 September 2015.

<http://www.hanhonggroup.com/nmr/nmr_en/B34317.html>Claridge, Timothy D. W. High-Resolution NMR Techniques in Organic

Chemistry. Amsterdam: Elsevier, 2009.Spectral Database for Organic Compounds SDBS. National Institute

of Advanced Industrial Science and Technology (AIST). Japan. Web. 20September 2015. <http://sdbs.db.aist.go.jp/sdbs/cgi-bin/ENTRANCE.cgi>

Since all of the proton assignments have been made, a 2-Dimensional gHMQC will help resolve the peaks thatpertain to the aromatic/alkene region. The gHMQCspectrum was recorded at 500 MHz (1H) with a spectralwidth of 6038.65 Hz in the direct dimension and 28409.1Hz in the indirect dimension. Figure 8 and 9 show the

NOESY NMR Spectrum

The two remaining unresolved aromatic protons will bedeciphered using a gCOSY experiment. Figure 5 representsthe aromatic region of a gCOSY spectrum that was recordedat 500 MHz (1H) with a spectral width of 6038.65 Hz and 1024complex points. We’ll start by inspecting the cross peakresonance that belongs to H5/H9.H5/H9, resonanceHB, is only coupledto H6/H8; Thus,H6/H8 is resonanceHD. By deduction weare able to assignresonance HE to H7.However, the gCOSYalso shows thatresonances HE andHD are coupled toeach other providingfurther evidence. Allof the protons havebeen assigned

13C DEPT NMR 1D Spectrum

The 13C DEPT spectrum was recorded at 500 MHz with aspectral width of 28409.1 Hz and a relax delay of 5s. The13C DEPT shows the hybridization of the carbons pertainingto cinnamaldehyde. All but one carbon is sp2 hybridized,tertiary carbons. We can assign resonance CC to atomicposition C4 located at 134 ppm.

ResultsBy careful analysis of the 1D and 2D spectra of all of theprotons and carbons have been assigned. We were ableto assign some protons directly based on the fine structureof the 1H-1D spectrum. The assignment ambiguities wereresolved using the NOESY and gCOSY experiments. Basedon the assigned protons, assignment of the directly boundcarbons was carried out using a gHMQC experiment. TheDEPT, which provides derived sub-spectral analysis of the1D-13C spectrum, provided key confirmation of resonanceassignments.

The 1H 1D NMR spectrum of cinnamaldehyde is shownin Figure 2. The spectrum data was recorded at 500MHz (1H) with a spectral width of 6038.65 Hz and 8192complex points. The solvent peak (CDCl3) appears at7.27 ppm. Resonance HA is the most downfield doublet

1H NMRAssignments (ppm)

H1 9.73

H2 6.74

H3 7.48

H5/H9 7.58

H6/H8 7.46

H7 7.45

The moleculehas twoalkeneprotons thatare trans toeach other. Inorder todistinguishbetween thetwo, splittingpatterns were

13C NMR Assignments(ppm)

C1 193.75

C2 131.30

C3 152.82

C4 134.01

C5 129.13

C6 128.62

C7 128.52

direct associationsbetween the protonand carbon nuclei.Consequently, CGcorrelates with H5/H9and is therefore C5.CB correlates with H3and is therefore C3,leading to CD beingC2, CE being C6/C8,and CF being C7. By

The remaining alkene proton,HC, is assigned to H3, a doublet(J=15.974Hz) found at 7.48 ppm.The aromatic region has a line ofsymmetry running through thecarbons labeled 4 and 7, givingrise to three unique aromaticproton and carbon resonances.In this molecule, C5 and C9, C6and C8, are considered to bechemically equivalent. Definitiveassignment of the remainingprotons requires 2D NMRexperimentation in order toresolve the remaining threeprotons.

gCOSY NMR Spectrum

Figure 4 shows the aromatic/alkene region of a NOESYexperiment. The NOESY was ran at 500 MHz (1H) with aspectral width of 6038.65 Hz and a MixN time of 500ms. Thecompletely conjugatedstructure ofcinnamaldehyde givessome rigidity to themolecule and places H5and H2, resonance HF,close enough toexperience the NuclearOverhauser Effect, NOE.By inspecting thecrosspeaks, it is observedthat H2 is only coupled toresonance HB. Therefore,resonance HB, thedoublet, belongs toH5/H9.

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 10

process of elimination,we can go ahead andassign peak CC to C4.Confirmation of theseassignments isaccomplished bycareful consideration ofthe results of the DEPTexperiment, Figure 10.

Figure 9

used. H3 would be split into a doublet by the protonbound to C2, whereas H2 would be split into a doubletof doublets due to the presence of the two surroundingnonequivalent protons at C3 and C1. Resonance F at6.74 ppm is a doublet of doublets (15.732 Hz, 7.538 Hz)and is assigned to H2.