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Analytical Chemistry
• Chromatography (Separations)
• Mass Spectrometry
• Infrared (IR) Spectroscopy
• Nuclear Magnetic Resonance (NMR) Spectroscopy
• X-ray Crystallography (visual solid state molecular structure)
What insights are we hoping to gain?
• Molecular Mass/Isotopic Distribution
• Molecular Formula
• Some Structural Characteristics – Fragmentation Pattern
Mass Spectrometry
Only molecules of the correct m/z (mass/charge) will make it to the detector.
Mass Spectromeric Isotope Indentification
EI-MS of 2,2-Dimethyl Pentane
Molecular ("parent") ion
Fragment ("daughter") ions
Base peak (largest signal)
Peaks with smaller m/z values __ called fragment ion peaks __
represent positively charged fragments of the parent molecule
EI-MS of 2,2-Dimethyl Pentane
Molecular iontert-butyl cation
(iso) propyl cation
Me Me
Me
methyl cation
ethyl cation
EI-MS of 2,2-Dimethyl Pentane
60
31
42
EI-MS of n-Propanol
EI-MS of 4-Heptanone
C3H7
OH
(iso) propyl cation
Molecular Ion
acylium ion
• +
EI-MS of 4-Heptanone
Molecular Ion
Why is there a signal higher than the Molecular ion?
EI-MS of 4-Heptanone
Isotopes
170 172
91
EI-MS of Benzyl Bromide
Isotopes
170 172
91
C7H779Br C7H7
81Br
Benzyl cation
EI-MS of Benzyl Bromide
EI-MS of 4-Chloroanisole
Isotopes
Isotopes