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Chapter 13 - Spectroscopy
Term | Definition |
---|---|
spectroscopy | process of measuring the E differences btwn the possible states of a molecular system by determining the freq of electromagnetic radiation (light) absorbed by the molecules |
IR spec | measures molecular vibrations (stretching, bending, rotation); must be a change in dipole moment so Br2 wouldnt show up |
fingerprint region | 1500-400cm |
Alcohol absorption | 3300cm |
Carbonyl abs | 1700cm |
ethers abs | 1100cm |
spec used for | identification of functional groups |
ketones abs | 1700cm |
acids abs | 2900-3300cm broad |
amines | sharp, 3100-3500cm |
NMR Spec | nuclear magnetic resonance spectroscopy; nuclei placed in magnetic field and align either with or against the direction of the field |
Alpha state | when it aligns with the field; low E |
Beta state | when nuclei aligns against the field; high E |
what is planted on x-axis for NMR | chemical shift in ppm |
coupling/splitting on spectrum | when different protons are within 3 bonds of each other |
doublet | two peaks of equal intensity equally spaced around true chemical shift |
UV Spec | useful for compunds with double bonds and hetero atoms with lone pairs |
Mass Spec | use an e- beam to ionize sample, accelerator to put the ions in flight and a magnetic field to deflect ions and detector counts the number of particles of each mass |
whats on the x-axis for mass spec | mass/charge; m/q |