Infrared Spectroscopy Flashcards
Technique that can be used in identifying the functional groups in a compound
Infrared Spectroscopy
In IR spectrometer, light passes through a sample which cause changes in the _____ of a molecule
Vibrational motions
IR spectrum has broad lines as compared to the sharp peaks in mass spectra. True or false
True
Functional groups give one or two bands in the _____ region at 4000-1500 cm^-1.
Functional group region
Refers to the area <1500 cm^-1 in IR spectrum
Fingerprint region
Wavenumber is proportional to wavelength. True or false
False. Energy/Frequency
In NMR spectroscopy, ___ and ___ are used to determine the number and type of H and C atoms, respectively in a molecule
1H NMR
13C NMR
Instrumentation:
A. Sample dissolved in solvent and placed in magnetic field
B. RF generator irradiates sample with short pulse.of radiation, causing resonance
C. When nuclei fall back to lower energy state, detector measures the energy release and a spectrum is recorded
Plot of intensity of pean against its chemical shift, measured in ppm
NMR Spectrum
NMR absorptions relatively appear as sharp peaks.
True
Most proton absorb between __
1-10 ppm
Describes relative location of peaks
Upfield, downfield
Used as external standard prior to NMR analysis
Tetramethylsilane (TMS)
NMR plots ___ vs. ___
Intensity and chemical shift
NMR performed to identify ___
Number and type of atoms
___ and ___ used for resonance are two variables that characterize NMR
Applied magnetic field, frequency of radiation
Energy in NMR
radiowaves or radiofrequency
Nucleus is in ___ when it absorbs RF radiation and spin flips to a higher energy state
Resonance
Equivalent protons do not split each others signal. ___ is observed for non equivalent protons on the same carbon or adjacent carbons
Spin-spin splitting
Loosely held pi electrons can either shield (NMR signal appears ___) or deshield (NMR signal appears ___) a nucleus
Upfield, downfield
IR plots ___ and ___
% transmittance and wavenumber
IR is performed to identify __
Functional groups
Recall general trend and important IR absorptions
Recall general trend and important IR absorptions
IR spectroscopy can be used for characterization of solid, liquid or gas samples
True
Describe sample preparation for the ff samples
Solids
Liquids
Gas
Mull, run in, case film, pressed pellet
Sandwiched using purified alkali halides like NaCl
Sample cells is made up of NaCl and KBr
IR soectrum has broad lines compared to sharo peaks in mass spectra
