NMR SPECTROSCOPY DR. M. KANJIA. Copyright reserved NMRS. Application to reproduce to Dr M Kanjia

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1 NMR SPECTROSCOPY DR. M. KANJIA Copyright reserved NMRS Application to reproduce to Dr M Kanjia

2 No. of Peaks Terminology Intensity Ratio n=0 One Peak Singlet 1 n=1 Three Peaks Triplet n= Five Peaks Quintet n=3 Seven Peaks Septet n= Nine Peaks Novetet I = 1 Deuterium ( D ), 1 N Pascal s Triangle I = 1 13 C NMR of CDCl3 I = 1 to 13 C Intensity ratio 1 : 1 : 1 Read the intensity ratio directly from Pascal Triangle.

3 T1 Relaxation T1 relaxation is an enthalpic process where the energy is taken from or transferred to neighbouring spins. The surrounding of the spins is called lattice hence T1 is also known as spin lattice relaxation. In this process the Z Component of the magnetization is return back to its equilibrium state. T1 values are useful information for NMR experiment what to set up as repetition time between each NMR scan. For 1 T1 values are from 0.5 Seconds to few seconds. Z Z Z Z Y Y Y Y X X X X Return of the Z component of the magnetization to the equilibrium state

4 Spin Lattice or Longitudinal Relaxation Process T 1 And the Measurement of 90 0 & Pulse width ( PW ) 13 C NMR Spectrum of Benzene in Acetone D 90 0 PW 30 0 PW 70 0 PW when sample is placed in the magnetic field and radio frequency (RF) pulse is applied, the Boltzmann population of spins get upset and after a time delay T 1 the Boltzmann population of spins get reestablished. This time delay T 1 is called the spin lattice or longitudinal relaxation time T 1 Measurement of 90 0 and pulses times knowledge of the 90 0 pulse time or pulse width ( PW ) for any spin active nucleus ( 1, 13 C, 19 F, 15 N ) is required to set up all multipulses FT NMR experiments. An accurate value of 90 0 PW is crucial for T 1 value measurement. This is usually obtained using a concentrated sample to produce a strong signal after a single pulse. Record the signal intensity with various PW. All measurements must be made with the same intensity scaling and same phase corrections. The intensities should show a sinusoidal variation with pulse time or pulse with PW 90 0 = A maximum positive signal 70 0 = A maximum negative signal = A zero signal 30 0 = A zero signal It is easier to determine the position of null values at and 30 0 PW The half of or quarter of 30 0 values will be 90 0 PW

5 Anisotropic Field in an Alkenes ( SP ) Anisotropic Field Effect Deshielded 1 Shift To Lower Field Away From TMS Field add C=C Secondary Magnetic Field Lines Induce Anisotropic Field o Applied Field

6 13 C NMR Spectrum of Cumene Aromatic 10 to 10 PPM Expansion C 5 C(C 3 ) Aromatic Benzene C(C3) C 1.00 PPM 1 C 3 & PPM C & PPM 5 3 C PPM Note :- C with Gives taller Peak ( Relaxation T 1 ) Both C 3.5 PPM eight of the peak is very important for assigning the chemical shifts C1 C has 1 C3 & 5 have eight ratio 1 : C 3.5 PPM C 1 has no hence smaller peak

7 13 C NMR Spectrum of 1,-Dimethylbenzene ( O-Xylene ) C 3 1 C 3 General Rule :- Carbons without Give smaller peak C (3,) PPM C (,5) 1.5 PPM 5 3 C & C5 are equivalent ( Identical ) C PPM e.g. C1 & C Carbon with more 1 relaxes faster than less 1 C (1, ) 13.5 C3 & C are equivalent ( Identical ) C1 & C are equivalent (Identical ) PPM Both C 3 are identical hence only One peak.

8 1 NMR Patter of Para Disubstituted Benzene When two groups X & Y become more similar then All NMR Peaks move closer hence Outer peaks get smaller and finally disappear but Inner peaks get taller and finally merge into single peak.

9 1 NMR Spectra of -Methyl Aniline and p-xylene only 8.5 to.5 PPM Region shown (3,5) (,) 3 C 3 5 N N (,3,5,) C 3 C 3 Aromatic Expansion

10 13 C NMR Spectrum of 1,-Dimethylbenzene ( p-xylene ) C 3 1 C, C3, C5, & C 19.7 PPM ( identical ) C1 & C PPM ( identical ) 5 C 3 3 Both C PPM

11 Analysis and interpretation of 1 & 13 C NMR Spectra of,-dinitromethylbenzene C 3 C 3 (NO ) 1 NMR Spectrum Integration 1.5 = 1 C 3.73 PPM C NO Expansion of aromatic region NO

12 Analysis and interpretation of 1 & 13 C NMR Spectra of,-dinitromethylbenzene C 3 C 3 (NO ) 1 NMR Spectrum C PPM Doublet Jmeta =.31 z PPM D of D Jmeta =.31 z Jortho = 8.7 z 5 1 NO 3 NO 7.3 PPM Doublet Jortho = 8.7 z Observation Jpara = 0.0 z

13 13 C NMR Spectra of,-dinitromethylbenzene C 3 C 3 (NO ) C5 1.8 PPM C 3 C PPM C PPM 1 NO C PPM C PPM C 15.9 PPM 5 3 C 18.3 PPM NO CDCl 3

14 Analysis and interpretation of 1 & 13 C NMR Spectra of Styrene C 5 -C=C 1 NMR Spectrum b 5.30 PPM c 5.81 PPM Integration 1 = 30 b a a.78 PPM c b c a Aromatic C 5 a c a b b c TRANS CIS GEMINAL

15 Analysis and interpretation of 1 & 13 C NMR Spectra of Styrene C 5 -C=C 1 NMR Spectrum b a a.78 PPM D of Doublet Jtrans = z Jcis = z c c 5.81 PPM D of Doublet Jtrans = z Jgem = 0.87 z b 5.30 PPM D of Doublet Jcis = z Jgem = 0.87 z a CopyRight Reserved NMR Spectroscopy 007 Application to c reproduce to Dr M Kanjia b

16 Analysis and interpretation of 1 & 13 C NMR Spectra of Styrene C 5 -C=C D COSY 1 NMR Spectrum b a c C 5 a c b

17 b a c C5 a c b Analysis and interpretation of D COSY 90 1 NMR Spectrum of Styrene C 5 -C=C 1. Every peak in spectrum gives the diagonal footprint in cosy spectrum.. Non coupled 1 gives only diagonal footprint and no footprint in X & Y axes. 3. Coupled 1 will give footprint in X & Y axes.. Number of coupling can be seen easily just by counting the number of footprints along either X or Y axis. In the Styrene a gives two footprints as shown by dashed arrows hence it is coupled to two 1 ( b & c ). Where as C5 give s no footprint in X & Y axes hence they are not coupled to any other 1 ( a, b or c ). No footprint in X CopyRight Reserved NMR Spectroscopy 007 Application & Y axes to reproduce to Dr M Kanjia 5. Aromatic region is complex to analyse.

18 Analysis and interpretation of 13 C NMR Spectrum of Styrene C 5 -C=C b 8 7 a C & C 18.8 PPM C PPM C PPM C PPM C3 & C PPM C PPM c 1 5 3

19 1 NMR spectrum of -Fluoro--Nitrophenol C 3 (F)(NO )(O) Integration 1 = PPM F 1 O NO O PPM PPM 3.9 PPM Impurity

20 1 NMR spectrum of -Fluoro--Nitrophenol C 3 (F)(NO )(O) O 3.9 PPM PPM 7.3 PPM F NO D of D of D xx = 8 Peaks Jpara-F J C-CF Jortho Jmeta Jortho Jmeta 5 3

21 13 C NMR spectrum of -Fluoro--Nitrophenol C 3 (F)(NO )(O) O F 1 NO C PPM C PPM 3 5 C PPM C PPM CDCl 3 C1 1. PPM C PPM

22 Expansion of 13 C NMR spectrum of -Fluoro--Nitrophenol C 3 (F)(NO )(O) O 19 F has long range coupling which can be seen in the following example C PPM C1 1. PPM 1 J C F = 50.0 z J C1 C F = z C PPM F NO C PPM 3 J C C3 C F = 7.z C PPM J C5 C C3 C F = 3.5 z J C3 C F = z C3 CopyRight CReserved NMR Spectroscopy 007 Application C1to reproduce to Dr M Kanjia C5 C

23 Analysis and interpretation of 1 & 13 C NMR Spectra of Pyridine C 5 5 N 1 NMR Spectrum 7.55 PPM Integration 1 = & 8.51 PPM 3 & PPM 5 3 1

24 The Electric Field Effect on Pyridine & Nitrobenzene Pyridine C 5 5 N Nitrobenzene C 5 NO Deshielded 1

25 Analysis and interpretation of 1 & 13 C NMR Spectra of Pyridine C 5 5 N 1 NMR Spectrum Expansion 5 3 & 8.51 PPM Jmeta = 1.81 z Jortho =.1 Z 7.55 PPM T of T Jortho = 7.5 z Jmeta = 1.81 z 1 3 & PPM Jortho = 7.5 z Jortho =.1 z Jmeta = 1.50 z

26 Analysis and interpretation of 13 C NMR Spectrum of Pyridine C 5 5 N C PPM 5 3 C & C PPM C3 & C PPM 1 N1 gives no signal in 13C NMR Spectrum