Spectroscopy Handout - Chem. 238, Spectroscopy Handout (Can...

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Chem. 238, Spectroscopy Handout (Can be used during tests) MS Major isotope masses and isotope “ratios” for use in mass spec calculations (the low mass isotope is arbitrarily listed as 100% for relative abundances. Atom M = abundance M+1 M+2 H 1 + 0.007826 (100%) 0.016 ----- C 12 + 0.000000 1.11 ----- N 14 + 0.0031 0.38 ----- O 16 0.0051 0.04 0.20 F 19 0.0016 ----- ----- S 32 0.0279 0.78 4.40 Cl 35 0.0311 ----- 32.6 Br 79 0.0817 ----- 98.0 The high precision M values are used to calculate an “exact mass” for the molecular ion M peak. Fragmentation – M • + goes to neutral radical plus a fragment ion (F + ) OR to a neutral molecule + F • + Common fragment series: R + (m/z = 14n + 1) and R C O + (m/z = 28 + 1 + 14n) UV - Vis Absorbed energies correspond to 40 – 120 kcal/mol, enough to promote HOMO to LUMO electronic excitations. Any strong absorbance at > 205 nm indicates conjugation. IR
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Spectroscopy Handout - Chem. 238, Spectroscopy Handout (Can...

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