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level: Level 2

Questions and Answers List

level questions: Level 2

QuestionAnswer
The principle behind this: the NUCLEUS of an atom placed in a MAGNETIC FIELD and exposed to ELECTROMAGNETIC RADIATION RESONATES at a specific frequency of that radiation.NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY (NMR)
NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY (NMR) APPLICATIONS1 For QUALITATIVE AND QUANTITATIVE STUDIESs of medicinal agent and other organic compounds 2 For CHARACTERIZATION OF THE EXACT STRUCTURE of raw materials and finished products 3 Can DETERMINE IMPURITIES W/OUT SEPARATION 4 NON-DESTRUCTIVE QUANTITATIVE ANALYSIS of drugs in formulation w/out prior separation 5 Potentially be used for FINGERPRINTING MIXTURES
NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY (NMR) STRENGTHS LIMITATIONSSTRENGTHS 1 Provides information about MOLECULAR STRUCTURE than any other technique 2 Results are REPRODUCIBLE 3 STABLE SYSTEM that does not need any instrument maintenance contract LIMITATIONS 1 INSENSITIVE technique for samples ˂1 mg for proton NMR and ˂ 5 mg for carbon-13 NMR 2 EXPENSIVE instrumentation requiring SPECIALIST operator
NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY (NMR) Instrumentation:1 Magnet w/ strong, stable, homogeneous field 2 Stable radiofrequency transmitter 3 Radio receiver and detector 4 Coil of wire surrounding the sample, w/c act as a sensor 5 Cell containing sample 6 Recorder to display absorption peaks
Quantitative NMR Reference use: __ - inexpensive - chemically unreactive - volatile (bp, 20C)Tetramethylsilane (TMS)
Quantitative NMR Sampling:1. solid or liquid sample is first dissolved in solvent free of protons (CCl4, CS2, CDCl3- deuterated chloroform) 2. added to NMR sample probe 3. followed by standard TMS Ex. assay of amyl nitrite
NMR Nuclei with ODD number of neutrons and ODD number of protons have a property of __ ODD atomic mass ODD atomic numberSPIN
NMR Nuclei with __ can interact with and respond to MAGNETSMagnetic Spin
NMR 1 Produced by magnets 2 Direction:. 1 Magnetic Field 2 North to South
NMR 1 Without magnetic field: __ 2 With magnetic field: __ - Same direction: __ - Opposite direction: __. 1 Random Orientation 2 Parallel Orientation - Same direction: Lower E - Opposite direction: Higher E
NMR Nuclei in the LOWER ENERGY state can transition to the higher state by __Absorbing RADIOFREQUENCY EMR
How NUCLEAR MAGNETIC RESONANCE works?1 Frequency varies among nuclei 2 Depends on the strength of magnetic field 3 Depends on the CHEMICAL ENVIRONMENT of a nucleus
Determined by nucleus' surrounding atoms Determined by nucleus' connectivity and relative position in a moleculeChemical Environment
Chemical Environment 1 Electrons have magnetic properties it __ external magnetic field 2 Electronegative nuclei withdraw electrons: __ 3 Adjacent atom of the electronegative atom is __, 1 BLOCKS 2 Shielded 3 De-shielded
Nuclei in different chemical environments absorb radiowaves of different frequencies. TRUE OR FALSETRUE
Effect of Shielding/ De-shielding varies on nucleus __ from electronegative atomdistance
1 Magnetic field causes nuclei to adopt __ 2 With NO applied magentic field, all spin states are __1 two spin orientations 2 degenerate
The frequency of RF Radiation which is absorbed induces __ which causes a PEAK to appear in the spectrum at the specific frequencyRESONANCE