Orgo 2 Ch14 - IR Spectroscopy, Mass Spectrometry

IR Region #1: 3,000 cm-1 C-H Bonds

IR Region #2: 3,000 cm-1 O-H and N-H Bonds

IR Region #3: 1,700 cm-1 Carbonyl C=O and Alkene C=C Bonds

IR Region #4: 2,200 cm-1 Nitrile C≡N and Alkyne C≡C Bonds

IR Region #5: Aromatic Compounds

All IR Regions

Common Bond Energy

Molecular Ion (M+)

Heaviest peak whose radical cation corresponds to weight of intact molecule. NOT always base peak.

Base Peak and Relative Abundance

Peak with highest relative abundance - reference measurement for % abundance (base peak is 100% relative abundance).

Favors stable radical species.

Isotope Split Peaks

Br: M+ and M+2 (~50%)

Cl: M+ and M+2 (~25%)

C: M+ and M+1 (~1%)

S: M+, M+1 (~1%) and M+2 (~4%)

Common Atomic Masses

Relative Abundance Ratios of Br and Cl

Rule of 13: M+ Weight to Base Formula

#C = (M+)//13
#H = #C + (M+)%13

Base Formula to Alternate Formulas - Substituents