Carbon-Carbon Bond Stretching ● Stronger bonds absorb at higher frequencies: >C-C 1200cm-1 >C=C 1660cm-1 >C=C 2200 cm-1 (weak or absent if internal) Conjugation lowers the frequency: >isolated C=C 1640-1680cm-1 >conjugated C=C 1620-1640 cm-1 >aromatic C=C approx.1600 cm-1 Chapter 12 Chapter 12 14 Carbon-Carbon Bond Stretching • Stronger bonds absorb at higher frequencies: ➢C-C 1200 cm-1 ➢C=C 1660 cm-1 ➢CC 2200 cm-1 (weak or absent if internal) • Conjugation lowers the frequency: ➢isolated C=C 1640-1680 cm-1 ➢conjugated C=C 1620-1640 cm-1 ➢aromatic C=C approx. 1600 cm-1 =>