WIDIASTUTI AGUSTINA ES, S.Si., M.Si. NUCLEAR MAGNETIC RESONANCE (NMR) WIDIASTUTI AGUSTINA ES, S.Si., M.Si.

Nuclear Magnetic Resonance Spectroscopy (NMR) : Spectroscopic technique that provide information about amount and type of atomic molecule Hydrogen atoms 1H NMR Carbon atoms 13C NMR Phosphor atoms 31P NMR

NUCLEAR SPIN ATOM Electron have quantum number ½ with a value of +1/2 and -1/2 - Spin Charge generates magnetic field so that electron act as a tiny magnet called a magnetic moment This effect also valid for another atom. An atomic nucleus has an odd number and atomic number of the odd or both will have to have spin and produced magnetic moment Nuclear Spin Rate depends on the quantum spin number , l, of nuclei

NUCLEAR SPIN NUMBER Number of spin state = 2 l +1 l = nuclear spin quantum number

Without magnetic field, both spin state have the same energy Nuclear atomic spin with + charge, generating a magnetic moment vector m + + m Without magnetic field, both spin state have the same energy + 1/2 - 1/2

IN MAGNETIC FIELD (BO)

RESONANCE In NMR spectroscopy, resonance is the energy absorption by the core-precision results in a change of spin nuclei from lower energy level to a higher energy level The precision results in a magnetic field oscillations and produce a "signal"

DE = hn quantized -1/2 -1/2 DE In a strong magnetic field, a rotating nuclei absorbs radio frequency (resonance phenomena) +1/2 +1/2 Bo Magnetic Field

LARMOR EQUATION n = Bo 2p g = frequency of the radiation that comes, which will cause the transition = giromagnetic ratio different for each atom (H, C, N) B0 = magnetic field

Magnetic Field In organic compounds, hydrogen atoms are surrounded by electrons moving in the presence of a magnetic field. The movement of electrons around the nuclei of hydrogen atoms in the magnetic field result in Diamagnetic Current The area around the atomic nucleus that is formed by electrons are called Diamagnetic Shielding B Induced (opposed Bo) Bo Applied

MEASUREMENT Liquid Sample Sample volume  0,5 mL Solvent 1H NMR = deuterated solvent CDCl3, CDOH3, Acetone-d6, Benzene-d6 Piridin-d5, DMSO-d6, D2O 13C NMR = CHCl3, CHOH3, Acetone, Benzene Piridin, DMSO, H2O Sampel Amount = ≤ 50 mg

1H NMR

INFORMATION FROM 1H NMR 1. Chemical Shift (, ppm), expressed as ppm (per million)  functional group 2. Integration  number of proton 3. Multiplicity (s, d, t, q, qi, sext., hept.)  proton relationship 4. Coupling Constant (J, Hz)  type of proton relationship  stereochemistry or position of proton 5. Proton Signal: 0-15 ppm

integration multiplicity Coupling constante ppm standart TMS Chemical shift H group = amount & type of proton

HYDROGEN EQUIVALENT Hydrogen Equivalent : Hydrogen that have a same chemical environtment Compounds that have one hydrogen equivalent, producing one peak of proton NMR

- Compounds that have two/three hydrogen equivalent, producing two/three peak of proton NMR

How many proton signal??

CHEMICAL SHIFT NMR signal is not measured by resonance position, but based on how far to shift from TMS, called CHEMICAL SHIFT Has a highly protected proton and carbon (appears on upfield region)

PROTON CHEMICAL SHIFT Proton chemical shift depends on the frequency of tool used (shear difference for protons appear the same but measured in different tools) TMS shift in Hz downfield n shift in Hz chemical shift = d = = ppm spectrometer frequency in MHz Any specific protons in a molecule will always appear at the same chemical shift (constant value)

PROTON CHEMICAL SHIFT

PROTON CHEMICAL SHIFT

PROTON CHEMICAL SHIFT Factors affecting proton chemical shift : Electronegatifity of the neighbour atoms Hibridisation from the adjacent atoms Diamagnetic Effect from the adjacent phi bond

Cl C H ELECTRONEGATIFITY d- d+ d- d+ Chlorine pull electron density away from carbon , caused electron density around the proton. Chlorine caused proton to be “deshields” Cl C H d- d+ electronegative NMR CHART Deshielding protons, appears at low field Shielding protons, appears at high field more deshielding

ELECTRONEGATIFITY Chemical Shift of X on CH3X CH3X CH3F CH3OH CH3Cl CH3Br CH3I CH4 (CH3)4Si X F O Cl Br I H Si Electronegativity of X 4.0 3.5 3.1 2.8 2.5 2.1 1.8 Geseran Kimia d 4.26 3.40 3.05 2.68 2.16 0.23 0 TMS Most deshielded

ELECTRONEGATIFITY "deshielding" effect increased with increasing number of electronegative atoms most deshielded CHCl3 CH2Cl2 CH3Cl 7.27 5.30 3.05 ppm “deshielding” effect decrease with increasing proton distance of electronegative atoms most deshielded -CH2-Br -CH2-CH2Br -CH2-CH2CH2Br 3.30 1.69 1.25 ppm

HIBRIDISATION

DIAMAGNETIC Magnetic Induction on phi bond causes the formation of pi bonds The presence of phi bond (double bond) or phi system will affect the chemical shift of nearby proton Accured on alkyne, alkene and benzene ring

- ALKYNE

- ALKENE

- BENZENE RING

SPLITTING SIGNAL On NMR spectrum, proton signals often do not appear as a single peak (singlet), but appear as doublet, triplet, quartet, and so on Spin-spin splitting on ​​the H atom is due to the interaction (coupling) with the neighboring H atom Spin-spin splitting followed the (n +1) RULES, if an Atom H has n non-equivalent H atoms which are neighbors, then the NMR spectrum of H atom signal will experience a breakdown as a (n +1) peaks

(n+1) RULES n = 1, the signal will be splitted as (1+1) peaks, doublet peaks, quartet

EXCEPTIONAL FOR (n+1) RULES Equivalent protons due to symmetry effects are usually not mutually spliting each other no splitting if x=y no splitting if x=y 2) Protons in the same group (tied to the same C) are usually not mutually splitting each other or

EXEPTIONAL FOR (n+1) RULES 3) N +1 rule applied to the protons in the aliphatic chain (saturated) or cyclic saturated. or YES YES But it is not applied to the protons of the double bond or benzene compounds NO NO

PASCAL TRIANGLE Splitting pattern similar with PASCAL TRIANGLE rule

SPLITTING PATTERN ( x = y ) ( x = y )

SPLITTING