CHMB42H3 Lecture 4: MASS SPEC
Document Summary
Determines the molecular mass and the molecular formula, as well as structural features. A small amount of a compound is introduced into an instrument where it is vaporized and then ionized (an electron is removed from each molecule) Electron ionization bombards the vaporized molecules with a beam of high-energy electrons. When the electron beam hits a molecule, it knocks out an electron producing a molecular ion. A molecular ion is a radical cation, a species with an unpaired electron and a positive charge. All the positively charged fragments of the molecule are drawn between two negatively charged plates, which accelerate the fragments into an analyzer tube. Neutral fragments are not accelerated - they are pumped out of the spectrometer. The analyzer tube is surrounded by a magnet whose magnetic eld de ects the positively charged fragments in a curved path.
