MPR-basics of NMR spectroscopy - Copy.pptx

Methods of pharmaceutucal research- NMR
M pharma 2nd send'
dr harisingh gour sagar university

1. Basics of NMR Spectroscopy

2. BASIC THEORETICAL BACKGROUND OF NMR SPECTROSCOPY Assignment of METHODS IN PHARMACEUTICAL RESEARCH (MPR) PHS C C 1201 Session 20 23-2024 Department of Pharmaceutical Sciences Dr. Harisingh Gour Vishwavidyalaya, Sagar, (M.P.) (A Central University) Supervisors: PROF. ASMITA GAJBHIYE DR. UDITA AGRAWAL MR.SHIVAM KORI MR.DEEPAK DWIVEDI Submitted by: ADARSH SHARMA Y 23254001

3. ACKNOWLEGEMENT I sincerely appreciate the assistance and support I received from my guide and other faculty members during my assignment PROF. ASMITA GAJBHIYE MAM, DR.UDITA AGRAWAL MAM, MR.SHIVAM KORI SIR AND MR. DEEPAK DWIVEDI SIR.

4. Contents: 1. INTRODUCTION 2. ABOUT NUCLEAR MAGNETIC RESONANCE(NMR) 3. PRINCIPLE 4.NMR SPECTRUM 5. INSTRUMENTATION 6.SOLVENT USED AND CHEMICAL SHIFT

5. 1. INTRODUCTION: What is Spectroscopy? The study of Electromagnetic Radiations (EMR) with matter, which may result in Absorption Transmission Reflection Emission The molecules, atoms, ions of sample move from one energy state to another energy state. Change can be from ground state to excited state or vice-versa. At ground state, energies are sum total of rotational, vibrational, electronic energies.

6. 2. Nuclear magnetic resonance (NMR): NMR Spectroscopy is a spectroscopic technique which is based on absorption of electromagnetic radiation in radio frequency region 4-900 MHz by nuclei of atoms. It is basically study of spin changes at the nuclear level when a radiofrequency is absorbed in presence of magnetic field. When proton(Hydrogen) is studied, then it is called as Proton Magnetic Resonance(PMR). It is one the most powerful tool in elucidating the number of hydrogen or proton in compound. Other nuclei studied are: 13 C 19 F 35 Cl 31 P

7. Nuclei with odd mass number only gives NMR Spectra like 1 H, 13 C, 35 Cl because they have asymmetrical charge distribution Spin quantum number for such nuclei will be 1/2, 3/2, 5/2 etc. For 1 H, it is 1/2. Other nuclei like 12 C, 16 O, 14 N, do not give NMR spectra because of symmetrical charge distribution and their spin quantum is integral value. The Spin Quantum Number describes the angular momentum of an electron . An electron spins around an axis and has both angular momentum and orbital angular momentum. Because angular momentum is a vector, the Spin Quantum Number has both a magnitude (1/2) and direction (+ or -). I Atomic Mass Atomic Number Examples Half-Integer Odd Odd 1 H Half-Integer Odd Even 13 C Integer Even Odd 2 H Zero Even Even 12 C Elements with odd mass or odd atomic number have property of nuclear spin.

8. 3. Principle :

9. 4. Nmr spectrum: The NMR Spectrum is plot of intensity of NMR Signals vs Magnetic Fields (Frequency) in reference to TMS. Tetramethylsilane (TMS) – internal reference compound for 1 H NMR. It has a strong, sharp resonance line from its 12 protons, with a chemical shift at low resonance frequency relative to almost all other  1 H resonances.

10. 4. instrumentation: 1.) Sample Holder Glass tubes with 8.5cm long; 0.3cm in diameter 2.) RF Transmitter Used to apply radiofrequency 3.)RF Receiver/ Detector To measure intensity of radiofrequencies emitted 4.)Permanent Magnets Provides homogenous magnetic field 60-100MHz 5.)Magnetic Coils Induces magnetic fields when current flows through it 6.)Sweep Generator To vary strength of applied magnetic fields ;to sweep magnetic field 7.)Recorder To record NMR Signal obtained

11. 5. Solvents used in nmr: 1.) CCl 4 - Carbon Tetrachloride 2.) CS 2 – Carbon Disulfide 3.) CDCl 3 - Deuteriocholoform 4.) C 6 D 6 – Hexa Deuteriobenzene 5.) D 2 O – Deuterium Oxide As we are analysing organic compounds for the nature, type, number and environment of Protons(Hydrogen), the solvent used in NMR spectroscopy should not contain Hydrogen atoms . Hydrogen is replaced by Deuterium . Properties of solvent: 1.) Chemical inertness 2.) Magnetic isotropy (magnetically neutral) 3.) Volatility 4.) Absence of Hydrogen atoms 5.) Easily available and Inexpensive

12. 6. Shielding and deshielding: 1.) Shielding of protons High electron density around a nucleus shields the nucleus from external magnetic field and the signals are upfield in NMR Spectrum. Closer to electropositive atom. More magnetic field required for excitation. 1.) Deshielding of protons Low electron density around a nucleus deshields the nucleus from external magnetic field and the signals are downfield in NMR Spectrum. Closer to electronegative atom. Less magnetic field required for excitation.

13. 7. Chemical shift: Theoretically for any organic compound, for all protons present only NMR signal should be recorded. But this does not happen in practice since all hydrogen atoms are not in same environment i.e. magnetic field applied is not felt by all hydrogen atoms uniformly. This happens due to presence of double and triple bonds; or aromatic, alicyclic ring system or electronegative atoms. Chemical shift is the difference between the absorption position of sample proton and the absorption position of reference compound. Chemical shift is measured in Ϩ values. The value ranges from 0 to 10 Ϩ for most of the compounds. TMS is most common reference compound set to Ϩ=0ppm. Factors affecting chemical shift: 1.) Electronegative groups : leads to deshielding, increasing chemical shift 2.) Magnetic anisotropy: non uniform magnetic field. Electrons in pie(carbonyls, alkenes, aromatic) systems interact with applied magnetic field which induces magnetic field causing anisotropy. - causes shielding and deshielding of protons 3.) Hydrogen bonding: More the Hydrogen bonding, more is the deshielding , chemical shift higher.

14. 7. Chemical shift:

15. References: 1.) Pavia D, Lampman G, Kriz G, Vyvyan J, "Introduction to Spectroscopy", Cengage Learning, 5th edition, 2013, Pg no: 215-255 2.) Shankar S, " Textbook of Pharmaceutical Analysis", Rx Publications , 5th edition, 2018, Pg no: 6-1: 6-9 3.) Chatwal G, Anand S, “ Instrumental methods of chemical analysis”, Himalaya publishing house, 2019, Pg no: 2.185-2.234 4.) Silverstein, R. M., F. X. Webster and D. J. Kiemle , Spectrometric Identification of Organic Compounds, 7th ed., John Wiley and Sons, 2005, Pg no: 500-550 5. Friebolin, H., Basic One- and Two-Dimensional NMR Spectroscopy, 5th ed., Wiley-VCH Publishers, New York, 2010