0

Guest

Courses New

Which has a greater -I effect, -OCH3 or -OH ? Please explain the reason.

Which has a greater -I effect, -OCH3 or -OH ? Please explain the reason.

Grade:

3 Answers

Vismay
13 Points
5 years ago
  • Of course -OH group as is given in the increasing order of the -I effect as it starts like this ---C+H2>--N+HHH3-O+H>..........and goes on.
Rajdeep
231 Points
5 years ago
HELLO THERE!
 
Negative inductive effect (-I effect) or electron withdrawing effect is shown by the groups which have more electronegativity.
 
OCH3 group is more electron withdrawing (i.e, shows more -I effect) than the OH group.
 
WHY?
 
The reason is that, there are two lone pairs of oxygen. Oxygen has a smaller size, so in case of OCH3, the methyl group is close to the lone pair electrons, which leads to Steric repulsion. Due to this, a slight positive charge is developed on Oxygen atom, and we know that positively charged ions are more electronegative, as they are electron deficient, and they definitely are in want of electrons. So, this positive charge increases the electronegativity of O atom, due to which its electron withdrawing effect increases.
 
However, in case of OH, the H atom is comparatively much much smaller than O, so here no Steric repulsion takes place. OH shows -I effect just due to the electronegativity value of Oxygen.
 
THANKS!
MALIK ABDUL WASEEM
15 Points
one year ago
OCH3 showed more eletron withdrwing effect compaired to OH even though CH3 is electron rich than H, There are two reasons for this anomlous behaviour.
O-H bond lenth is shorter and weak asewell. The weak bond of O-H means the electron cloud Shaired between H and O is more towards O, which brings more -ve charge on oxygen ( actully here we have -O-ev and H+)  this made OH A  less electron widrawing. While as the bond between O and CH3 is having suffecent bond length, strength aswell and only inductive effective is oprative, only delta -ve charge is carried by O which is less compaired when OH is there. (Claden and Grives Book) 

Think You Can Provide A Better Answer ?

Other Related Questions on Organic Chemistry

View all Questions »

ASK QUESTION

Get your questions answered by the expert for free

Answer and earn gift vouchers

Win Gift vouchers upto Rs 500/-

View courses by askIITians

Design classes One-on-One in your own way with Top IITians/Medical Professionals

Click Here Know More

Complete Self Study Package designed by Industry Leading Experts

Click Here Know More

Live 1-1 coding classes to unleash the Creator in your Child

Click Here Know More

a Complete All-in-One Study package Fully Loaded inside a Tablet!

Click Here Know More