CHEMICAL SHIFT

• WHAT IS CHEMICAL SHIFT MEASURED IN?

  parts per million (ppm)
• WHAT IS THE STANDARD FOR CHEMICAL SHIFT?

  tetramethylsilane (TMS) = defined 0
• WHAT IS CHEMICAL SHIFT?

  related to difference in frequency between resonating nucleus and that of TMS
• WHAT CAUSES DIFFERENT CHEMICAL SHIFT VALUES?

  carbon atoms in different environments
• EXAMPLE OF A CAUSE OF A DIFFERENT CHEMICAL SHIFT VALUE?

  • near electronegative O atom
  • O withdraws electrons
  • C atom is deshielded
  • feels greater magnetic field
  • resonates at a higher frequency
  • greater chemical shift value