text: Relative inductive effects have been experimentally measured through the resulting s of a nearby carboxylic acid group (see ).  In increasing order of -I effect or decreasing order of +I effect, common functional groups are:
  Hydrogen subsituents also exhibit an isotope effect: relative to the same order,
  where H is hydrogen, D deuterium, and T tritium. 
  The strength of inductive effect is also dependent on the distance between the substituent group and the main group that react; the longer the distance, the weaker the effect.
  Inductive effects can be expressed quantitatively through the Hammett equation, which describes the relationship between reaction rates and equilibrium constants with respect to substituent.