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Spectroscopy (Nuclear Magnetic resonance (NMR) spectroscopy (chemical…
Spectroscopy
Nuclear Magnetic resonance (NMR) spectroscopy
lamor frequency (equation)
When the elecctromagnetic Radiation Matches the lamor frequency the nucleus Comes into resonance and energy is absorbed to promote the nucleus to a higher energy spin
NMR experiments
the ppm scale (equation)
chemical shift in organic molecules
Protones attached to a C atom
Protones attached to an O atom
Aldehydes and carboxylic acids
Aromatic systems
Chemical shift (equation)
shielding
spin-spin coupling
Electronic spectroscopy (UV/vis spectroscopy)
Electron transition
measuring the wavelength at which this occures-> bonding
Change in orbitals-> Change in energy
Electron energy is quantized: related to the radius of the orbital
Conjugated (Polyunsaturated) Hydrocarbons
starting from 163 nm adding 30 nm per additional C=C bond
Quantitative Spectroscopy
Position of Peaks: due to the energy of the transition
Size (intensity) of Peaks depends of the Umber of absorptions
Important factors
concentration
Path length
how many molecules within the sample are in the correct energy state to absorb light at this wavelength
How likely is the transition
Beer-Lambert Law
Fluorescence Spectroscopy
Fluorescence
Phosphoresence
Light
Speed in vacuum
Colour ranges
Light energy (De-Broglier´s relationship)
Planck´s Equation for light energy
Chromophores
Infrared (IR) Spectroscopy
Vibrational modes
Vibration of a Diatomic molecule
Factors influencing the Vibration: Mass and stiffness of the string (k)
reduced mass (kg)-> (equation)
characteristic vibrational frequency(equation)
wavenumber (1/cm): devide vibrational frequency by the Speed of light
reduced mass in isotopes(equation)
Hooke`s Law (restored force)(equation)
Estimate force constant from measured IR frequency (equation)
common frequencies:
O-H stretching
N-H vibration
C-H
Saturated
stretching and bending
Unsaturated
C-H double and tripple bond
C=O stretching
Transforming IR Transmission into Absorbance scale (equation)
Dipole Moment (intensity)
wavenumber is directly proportional to ist force constant (equation)