-OH when used as -I effect and +I effect?

[Indranil]

Homework Statement

Is -OH used both -I effect and +I effect? When used it -I effect and +I effect?

Homework Equations

Is -OH used both -I effect and +I effect? When used it -I effect and +I effect?

The Attempt at a Solution

I only know that -OH used as -I affect because 'O' is more electronegative.

 

[TeethWhitener]

I only know that -OH used as -I affect because 'O' is more electronegative.

In what systems do you know this to be true?

Edit: here's a big hint: think about resonance.