Lewis vs. Bronsted acids/bases

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Christina Kim 4A
Posts: 7
Joined: Fri Sep 25, 2015 3:00 am

Lewis vs. Bronsted acids/bases

Postby Christina Kim 4A » Wed Dec 02, 2015 2:52 pm

How do you determine which process is a Lewis acid/base reaction, but is not a Bronsted acid/base reaction?

Alli Foreman 2H
Posts: 26
Joined: Fri Sep 25, 2015 3:00 am

Re: Lewis vs. Bronsted acids/bases

Postby Alli Foreman 2H » Wed Dec 02, 2015 4:27 pm

The difference between these two definitions has to do with the particle being transferred. Lewis acids are electron acceptors while Bronsted acids are proton donators. Lewis bases are electron donators while Bronsted bases are proton acceptors. In a reaction with a Bronsted acid, the acid would lose an H atom (which is essentially a proton). In a reaction with a Lewis acid, the acid would gain an electron pair.

Chem_Mod
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Re: Lewis vs. Bronsted acids/bases

Postby Chem_Mod » Wed Dec 02, 2015 4:28 pm

If electrons are transferred but no protons are transferred, it is a Lewis pair and not a Bronsted pair.

For example, BF3 + F- --> BF4-
BF3 is lewis acid and accepted electrons
F- is lewis base and donated electrons
nowhere was there a proton transfer so these are not Bronsted

on the other hand, all Bronsted acid/base are automatically Lewis acid/base

K Phelan 3D
Posts: 23
Joined: Wed Sep 21, 2016 2:59 pm

Re: Lewis vs. Bronsted acids/bases

Postby K Phelan 3D » Wed Nov 16, 2016 12:33 pm

When identifying acids and bases in this overall Acids and Bases section of the course, do we generally use the Bronsted definition or the Lewis definition to identify acids/bases?

Alex Uy 2D
Posts: 23
Joined: Sat Jul 09, 2016 3:00 am

Re: Lewis vs. Bronsted acids/bases

Postby Alex Uy 2D » Wed Nov 16, 2016 5:32 pm

How does an atom donate a proton? We have been learning about electrons being shared and electronegativity, but I thought a proton is part of the nucleus of an atom. How does a proton separate from an atom?

edhuang
Posts: 24
Joined: Wed Sep 21, 2016 2:58 pm

Re: Lewis vs. Bronsted acids/bases

Postby edhuang » Wed Nov 16, 2016 6:27 pm

Atoms generally do not donate protons. Protons do not tend to leave an atom, and do not tend to get added to the atom, generally speaking, unless we are talking about nuclear chemistry in which nuclear reactions cause this to happen. When protons are added to an atom, the atom becomes another element. Nevertheless, we are only talking about electron donation here.


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