Structural elucidation by NMR(1HNMR)

NMR examples

1. STRUCTRAL ELUCIDATION BY NMR(Proton) 1 By: Nilam Ghadagepatil . M. Pharm 1 st sem. (PHARM. QUALITY ASSURANCE) Guided by: Prof. Amol Bansode. Date:21-feb-2022

2. INDEX 1.Intoduction 2.NMR spectroscopy types. 3.Priniciple. 4. 1 H NMR. 5. Structural Elucidation . Application. 2

3. 3 Introduction : NMR : Nuclear M agnetic Resonance(NMR) is spectroscopy technique which is based on the absorption of electromagnetic radiation in the radio frequency region 4 to 900 Mhz by nuclei of the atoms. P NMR : Proton Nuclear Magnetic Resonance spectroscopy is one of the most powerful tools for elucidating the number of hydrogen or proton in the compound.

4. NMR Spectroscopy 1.Proton( 1 H ) nuclear magnetic resonance (PMR or 1 H-NMR) . 2.Carbon ( 13 C)nuclear magnetic resonance( 13 C-NMR ). 3.Two Dimensional NMR (2D-NMR ). 4

5. Principle of 1 H NMR : The principle behind NMR is that many nuclei have spin and all nuclei are electrically charged. If an external magnetic field is applied ,an energy transfer is possible between the base energy to higher energy level. 5

6. When proton is not in electric field proton are arranged in randomly . When electric field is applied proton arrange in antiparallel or parallel . Parallel =+ 1/2 Antiparallel=- 1/2 6

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8. Chemical shift The position on the plot at which the nuclei absorbs is called the chemical shift . or A Chemical Shift is defined as difference in parts per million(ppm) between the resonance frequency of the observed proton and tetramethylsilane (TMS) hydrogens. The NMR spectrum is plot of intensity of NMR signals VS magnetic field in reference to TMS. 8

9. Shielding of proton: High electron density around a nucleus shields the nucleus from the external magnetic field and signal are up field in the NMR spectrum . Deshielding of proton: Lower electron density around a nucleus Deshields the nucleus from the external magnetic field and the signals are downfield in the NMR spectrum. 9

10. Example : A . R-CH 2 -R (alkyl) electron donating-up field A B B.R-CH 2 -Cl(Halogen) electron withdrawing-downfield 10

11. 1 H -NMR Nuclear Magnetic resonance spectroscopy Study of nucleus 11 O OH CH3 CH3 H3C

12. WHAT IS INSIDE THE NUCLEUS 12 1 Nucleus=Protons + Neutrons 2 These protons and neutrons spin around their own axis. 3. Each spin has magnitude of ½. 4. Magnitude of the spin of nucleus is because of Protons and Neutrons(overall spin of the nucleus depend on spin of P and N) 5. If these spins are paired against each other , the nucleus of that atom posses NO overall spin.

13. If the number of neutrons and the number of protons are both even , then the nucleus has No spin If the number of neutrons and the number of protons are both odd then the nucleus has an integer spin (i.e.1,2,3) If the number of neutrons plus t he number of protons is odd ,then the nucleus has a half-integer spin(1/2,3/2,5/2).so, 1 1 H and 6 13 C can be studied 13

14. Nucleus of 12 C=6P+6 N Nucleus of 13 C=6P+7N 14 P+N

15. 1 H-NMR=PROTON NMR=PMR In the nucleus of hydrogen there is only one proton ,which is responsible for the overall spin of hydrogen nucleus. So when we study hydrogen nucleus means we are studying the spinning proton hence we call it as proton NMR or PMR . Spin Quantum Number: Spin quantum number describes the angular momentum of an electron. 15

16. 1 H-NMR spectrum : 16

17. 1.Number of peak in 1H-NMR spectrum : Number of sets of chemically equivalent protons Protons in different environments give different NMR signals. Protons in same chemical environment are called as equivalent protons and such equivalent protons give the same NMR signal 17 H 3 C O CH 3 H 3 C Cl O H 3 C CH 3 6 H Ha Hb Ha Hb Hc 1 peak 2 peak 3 peaks

18. Intensity of peak : Peak height 1.Number of signals=5 2.Peak intensity= Hc >Ha>Hb/Hd >He o OH CH3 CH3 H3C

19. 3.Position of signals: Chemical shift: He-Electronegative so it is in downfield region 19 O OH CH3 CH3 H3C

20. TMS 20 12 11 10 9 8 7 6 5 4 3 2 1 0 Chemical shift(ppm) Intens I t y

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23. 4.Peak multiplicity/Peak splitting due to spin spin coupling:N+1 rule 23

24. Multiplicity – The Spin-Spin Splitting Depending on how many neighbors it has, the signal of a given proton can be  split into lines . The simplest signal consists of one line and is called a  singlet , followed by the  doublet ,  triplet , etc. A signal with more than seven lines is referred to as a  multiplet . The number of peaks is obtained by the   N+1 rule ,  where  N is the number of neighboring protons .  For example, if the proton has  one neighbor , it gives a  doublet  (1+1), if there are  two adjacent protons , we get a  triplet  (2+1). 24

25. ( 1,1,2-trichloroethane) n+ 1=2+1=3=triplet n+1=1+1=2=doublet 2. Ethyliodide n+1=3+1=4=quartet n+1=2+1=triplet n+1=3+1=4=quartet n+1=2+1=triplet 25

26. He=singlet n+1=0+1= 1 Hd=singlet n+1=0+1= 1 Hc =singlet n+1=0+1= 1 Hb=quartet n+1=3+1= 4 Ha=triplet n+1=2+1= 3 26 O OH CH3 CH3 H3C

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28. 1H NMR Absorption by type of compound A.Alkanes M.Carboxylic Acid B.Alkenes N. Amides C.Aromatic compounds O. Nitroalkanes D.Alkynes E.Alkyl Halides F.Alcohols G.Ethers H.Amines I.Nitriles J.Aldehydes K.ketones L.Esters 28

29. Octane a.1.26 b. 0.88 29 A.ALKANES

30. B. Alkenes 2-methyl-1-pentene a.4.68 b.1.980 c.1.703 d .1.47 e.0.90 30 a b c d e

31. C . Aromatic Compound alpha- chloro -p-xylene a.7.363 b.4.558 31

32. D.Alkynes 1pentyne a.2.15 b.1.936 c.1.55 d.1.00 32 A B D C

33. E.Alkyl Halides 1-chlorobutane a.0.916 b.1.413 c.1.683 c.3.42 33

34. F.Alcohols 2-methyl-1-propanol a.3.391 b.2.07 c.1.75 d.0.920 34

35. G.Ethers Butyl methyl ether a .0.9 e.3.4 b.1.5 d.3.5 c.1.7 35

36. H.Amines: Propylamine a.2.653 b.1.45 c.1.24 d.0.92 36

37. I.Nitriles Valeronitrile a.2.342 b.1.63 c.1.50 d.0.959 37

38. J.Aldehydes: 2methyl-1propanal a.3.391 b.2.07 c.1.75 d.0920 38

39. K.Ketones 5-methyl-2-hexanone a.2.418 b.2.137 c.1.64-1.35 d.0.89 39

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41. L .Esters Isobutyl acetate a.0.94 b.1.93 c.2.054 d.3.849 41

42. M . Carboxylic acid Dimethylmalonic acid a.1.285 42

43. T oluene 43

44.   1 H-NMR spectrum of  primary amine  functional phenol/aniline benzoxazine monomer. 44

45. COCAINE Purity measurement of a caffeine sample with TCNB as internal reference. From the peak integrals, the purity is calculated to be 97.8%. 45

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47. APPLICATION 47 Bacterial identification and metabolic studies 1 H NMR spectroscopy has been used for bacterial identification and quantification and for metabolic pathways studies. Several studies have been conducted for the diagnosis of the bacteria that cause urinary tract infections (UTI).  Antimicrobial susceptibility assays The use of  1 H NMR spectroscopy for antimicrobial susceptibly tests has been not highly studied despite its powerful utility in this area of study [ 5 ]. Application of  1 H NMR spectroscopy to antimicrobial susceptibility studies was first carried out on  Applications in bio fluids In the last few years,  1 H NMR has been used to directly analyse biofluids and to diagnose different diseases directly from body fluids. In this sense, it has been applied to analyse human microbiota from faeces and urine samples Other types of analyses The combination of NMR spectroscopy, with the use of isotopically substituted molecules as tracers is a well‐established protocol in microbiology.

48. REFEENCE Pavia DL, Lampman GM, Kriz GS. Introduction to Spectroscopy third edition. Thomson Learning, Inc. 2001. p. 579. Webb GA. NMR Spectroscopy. Annu Reports Prog Chem - Sect C. 1992;89(December):3–36. https://m.chemicalbook.com/SpectrumEN_627-05-4_MS.htm https://www.sciencedirect.com/topics/chemistry/1h-nmr-spectrum 48