shielding& deshielding effect by irfaan

* SHIELDING &DESHIELDInG EFFECT * : 

* SHIELDING &DESHIELDInG EFFECT * By Mohammed Irfaan 07T61R0049 VI th Year , B.pharmacy Azad College Of Pharmacy PHARMCEUTICAL ANALYSIS

OUTLINE OF PRESENTATION : 

OUTLINE OF PRESENTATION Introduction Of NMR Spectroscopy Chemical shift Shielding And Deshielding Effect Factors influencing chemical shift

Nmr spectroscopy : 

Nmr spectroscopy * Nuclear Magnetic Resonance Spectroscopy *

NMR Spectroscopy - Intro : 

NMR Spectroscopy - Intro The study of spin changes at the nuclear level when radio frequency energy is absorbed in the presence of magnetic field. Measures the absorption of EM radiation in the radiofrequency region 4 MHz to 750 MHz (wavelength 0.4 m to 75 m) Most commonly done on 1H and 13C. OBJECTIVES : Structural elucidation Drug design MRI

NMR in Everyday Life : 

NMR in Everyday Life Magnetic Resonance Imaging

Slide 6: 

PRINCIPLE OF NMR

Principle of NMR : 

Principle of NMR * Measures nuclear magnetism or changes in nuclear magnetism in a molecule * NMR spectroscopy measures the absorption of light (radio waves) due to changes in nuclear spin orientation * NMR only occurs when a sample is in a strong magnetic field *Different nuclei absorb at different energies (frequencies)

A Modern NMR Instrument : 

A Modern NMR Instrument Radio Wave Transceiver

Different Types of NMR : 

Different Types of NMR Electron Spin Resonance (ESR) 1-10 GHz (frequency) used in analyzing free radicals (unpaired electrons) Magnetic Resonance Imaging (MRI) 50-300 MHz (frequency) for diagnostic imaging of soft tissues (water detection) NMR Spectroscopy (MRS) 300-900 MHz (frequency) primarily used for compound ID and characterization

Which Elements or Molecules are NMR Active? : 

Which Elements or Molecules are NMR Active? * Any atom or element with an odd number of neutrons and/or an odd number of protons * Any molecule with NMR active atoms 1H - 1 proton, no neutrons, AW = 1 13C - 6 protons, 7 neutrons, AW =13 15N - 7 protons, 8 neutrons, AW = 15 19F = 9 protons, 10 neutrons, AW = 19

NMR Units of Measurement : 

NMR Units of Measurement Energies ~ 10-6 eV Wavelength ~ 30 cm - 100 cm Frequency ~ 108 - 109 Hz Parts per million (d) 0 - 12 ppm (for 1H) ppm = nobs - nref nref x 106 ppm is proportional to frequency

Bigger Magnets are Better : 

Bigger Magnets are Better

NMR Spectrum : 

NMR Spectrum A Spectrum of Absorption of Radiation Vs. Applied Magnetic Strength is called as NMR Spectrum.

Slide 14: 

14 The spectrum is measured on a delta (d) scale in units of parts per million (ppm) Lower frequency is to the left in the spectrum; these absorptions are said to be downfield Higher frequency is to the right in the spectrum: these absorptions are said to be upfield The small signal at d 0 corresponds to an internal standard called tetramethylsilane (TMS) used to calibrate the chemical shift scale The number of signals in the spectrum corresponds to the number of unique sets of protons

CHEMICAL SHIFT () : 

CHEMICAL SHIFT () * The variations of nuclear magnetic resonance frequencies of the same kind of nucleus, due to variations in the electron distribution Chemical Shift = Absorption Frequency relative to TMS (Hz) Spectrometer Frequency (MHz)

Slide 16: 

*Key to the utility of NMR in chemistry Different 1H in different molecules exhibit different absorption frequencies *Arise from the electron cloud effects of nearby atoms or bonds, which act as little magnets to shift absorption n up or down *Mostly affected by electronegativity of neighbouring atoms or groups

Tetra methylsilane (TMS) : 

Tetra methylsilane (TMS) Only one peak on NMR spectrum High electronic density of H in TMS. Almost all the H peaks of organic compounds appear on the left of the TMS peak.

CHARACTERISTIC CHEMICAL SHIFTS : 

CHARACTERISTIC CHEMICAL SHIFTS

Slide 19: 

Shielding and Deshielding of Protons SHIELDING EFFECT Protons in an external magnetic field absorb at different frequencies depending on the electron density around that proton High electron density around a nucleus shields the nucleus from the external magnetic field Shielding causes absorption of energy at higher frequencies (more energy is required for this nucleus to flip between spin states) - the signals are upfield in the NMR spectrum

DESHIELDING EFFECT : 

DESHIELDING EFFECT Lower electron density around a nucleus deshields the nucleus from the external magnetic field * Deshielding causes absorption of energy at lower frequencies (less energy is required for this nucleus to flip between spin states) – the signals are downfield in the NMR spectrum

Shielding & Deshielding Scale : 

Shielding & Deshielding Scale

FACTORS INFLUENCING CHEMICAL SHIFT : 

FACTORS INFLUENCING CHEMICAL SHIFT Both 1H and 13C Chemical shifts are related to the following major factors: Depends on Hydrogen bonding Depends on adjacent group Depends on carbon group attached Depends on hybridization Depends on anisotropy

APPLICATIONS : 

APPLICATIONS *Analysis of blood, urine and other biofluid mixtures to quantify and identify metabolite changes *Allows one to detect drug toxicity and even localize toxicity (for preclinical trials) in a non-invasive way *Detection, identification and quantitation of primary and secondary drug metabolites

Other Applications : 

Other Applications * Clinical testing (detection of inborn errors of metabolism, cancer, diabetes, organic solvent poisoning, drugs of abuse, etc. etc.) * Cholesterol and lipoprotein testing * Chemical Shift Imaging (MRI + MRS) *Pharmaceutical Biotechnology (proteins, protein drugs, SAR by NMR

REFERENCE : 

REFERENCE WEBSITES http://redpoll.pharmacy.ualberta.ca http://www.pharmacy.ualberta.ca/pharm325/ www.wikipedia.com BOOKS PHARMACEUTICAL ANALYSIS VOL II BY DR A.V KASTURE , DR S.G WADODKAR INSTANT NOTES IN ANALYTICAL CHEMISTRY BY D .KEALEY PHARMACEUTICAL ANALYSIS BY R.S . RAVISHANKAR

* By - MOHAMMED IRFAAN : 

* By - MOHAMMED IRFAAN