OChem 2: Ch14 Terms

OChem 2, Chapters 14

Infrared Spectroscopy (IR)

• bonds bend, stretch, or twist

  • DOES NOT BREAK

Compounds w/ IR: 2700-4000 cm-1

• OH

• NH

• CH

Compounds w/ IR: 2100-2300 cm-1

• C≡C

• C≡N

Compounds w/ IR: 1600-1850 cm-1

• C=C

• C=O

• C=N

Compounds w/ IR: 400-1600 cm-1

FINGERPRINT REGION

• C-C

• C-O

• C-N

Parent Peak

• molecular weight of entire compound

• the rightmost cluster

  • and tallest in that cluster

Base Peak

• most abundant cluster

M⁺

• Parent Peak

  • always lower isotope number

Ex.

• ¹²C, ⁷⁹Br, ³⁵Cl

M+1 or M+2

• isotope peak

  • always higher isotope number

Ex.

• ¹³C, ⁸¹Br, ³⁷Cl

Ratio for C Isotopes

• ¹²C = 99%

• ¹³C = 11%

Ratio for Br Isotopes

• ⁷⁹Br = 50%

• ⁸¹Br = 50%

Ratio for Cl Isotopes

• ³⁵Cl = 75%

• ³⁷Cl = 25%

vice versa percentages

Nitrogen Rule

• odd MW = 1 or odd # of Nitrogens

• even MW = 0 or even # of Nitrogens

Hydrogen Deficiency Formula

HD = 2C + 2 + N - H - X / 2