NUCLEAR MAGNETIC RESONANCE
QUANTITATIVE AND QUALITATIVE APLICATIONS OF NMR
NMR spectroscopy is a powerful analytical technique used for studying molecular structure and dynamics.
QUANTITATIVE APPLICATIONS
1-QUANTIFIACTION OF COMPOUNDS : - NMR is used to quantify the concentration of compounds present in sample because area under the signal in NMR spectrum is directly proportional to the no. of nuclei.
- ABSOLUTE QUANTIFICATION : - By integrating spectrum peaks ,we can calculate the concentration of substance without reference standards.
- RELATIVE QUANTIFICATION : - By using internal and external standards, relative quantities of compounds can be determined . A known concentration of standard compound is added and the ratio of integrals is used to determined the concentration if analyte.
2- PURITY ANALYSIS :- NMR can accurately quantify the purity of a sample by comparing the signal intensities of a target compound with possible impurities. By integrating NMR peaks corresponding to different chemical species , we can possibly access how much compound is preset verses impurities.
3- KINETIC AND REACTION MONITORING : - QNMR is used to monitor the kinetics and mechanism of a chemical reaction. By examining the change in peak intensities of reactants and products with time, we can quantify the reaction mechanism and rates.
4- DETERMINATION OF ENANTIOMARES : - On the basis of chirality and sample derivatization, we can distinguish between enantiomers and determine the ratio of each form crucial for pharmaceutical development.
5- MIXTURE ANALYSIS :- In pharmaceutics, food sciences and environmental tests etc. to determined concentration of various components in complex mixtures with no need of prior separation QNMR is used.
QUALITATIVE APPLICATIONS
1- SUTRUCTURAL ANALYSIS :- Various types of NMR like 1H, 13C and 15N NMR illustrate the chemical environment of nuclei and molecular structure.
- SPIN-SPIN COUPLING :- We can examine the behavior of neighbor atoms through coupling patterns. (J-coupling).
- MULTIPLICITY ANALYSIS :- We can determine the no. of neighbor atoms involving in coupling with observed nucleus.
- CHEMICAL SHIFTS :- We can examine the electronic environment around the nuclei and types of bonds and functional groups present.
2- CONFORMATIONAL ANALYSIS :- We can analyze three dimensional conformations of molecules in solution. Analyzing molecular parts interacting with each other through space and helps the researchers to prefer the dynamics of flexible molecules .
- NUCLEAR OVERHAUSER EFFECT SPECTROSCOPY :- A qualitative technique which gives information about spatial proximity between atoms within a molecule like proteins and nucleic acids.
- ROTATING FRAME OVERHAUSER EFFECT SPECTROSCOPY :- Analyzing spatial relationships with in a system where NOE signals are week due to fast molecular motion.
3- CHEMICAL ENVIRONMENT & FUNCTIONAL GROUP IDENTIFICATION : - NMR helps to detect functional groups on basis of their specific chemical shift and coupling constants.
- ALCOHALS shows broad singlets due to proton exchange.
- AROMATIC COMPOUNDS show downfield signals due to desheilding effect.
- EXCHANGE PHENOMENNA :- We can examine conformers, tautomeric forms by monitoring exchange process between different molecular states.
- RELAXATION TIME (T1 & T2 ) :- Relaxation time informs about motion, vibration and interaction of molecules with their environment.
- MAGIC ANGLE SPINNING :- High resolution study of solids due to high speed spinning of sample.
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