Electron Donating/Accepting

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Siddiq 1E
Posts: 106
Joined: Fri Aug 09, 2019 12:15 am

Electron Donating/Accepting

Postby Siddiq 1E » Mon Dec 02, 2019 5:25 pm

I'm confused about how lewis acids accept electrons? And how do lewis bases donate electron pairs? I get Bronsted acids and bases do proton accepting/donating through Hydrogens but I don't know how lewis acids/bases work. Thanks in advance :)

NRobbins_1K
Posts: 54
Joined: Sat Aug 17, 2019 12:15 am

Re: Electron Donating/Accepting

Postby NRobbins_1K » Mon Dec 02, 2019 5:41 pm

We talked about Lewis acids and bases mostly in the context of coordination compounds, so I'll explain it in that context too.

In a coordination compound, the Lewis acid (electron pair acceptor) is the positively charged transition metal. Notice that even though it is positively charged, !! it doesn't have an extra H+ or proton to donate and therefore can't directly form hydronium ions in solution.!! However, because of its positive charge, it can easily form bonds with negatively charged species (which have extra electrons) and 'accept' their lone pairs. As in the case of iron chloride that we learned about in class today, the end result is the same, because due to iron's strong positive charge the species that bind to iron eventually give off a proton anyway. However, since iron chloride does not directly give off a proton it cannot be called a Bronsted acid even though it still has the same effect of lowering the pH.

Siddiq 1E
Posts: 106
Joined: Fri Aug 09, 2019 12:15 am

Re: Electron Donating/Accepting

Postby Siddiq 1E » Mon Dec 02, 2019 6:17 pm

NRobbins_1K wrote:We talked about Lewis acids and bases mostly in the context of coordination compounds, so I'll explain it in that context too.

In a coordination compound, the Lewis acid (electron pair acceptor) is the positively charged transition metal. Notice that even though it is positively charged, !! it doesn't have an extra H+ or proton to donate and therefore can't directly form hydronium ions in solution.!! However, because of its positive charge, it can easily form bonds with negatively charged species (which have extra electrons) and 'accept' their lone pairs. As in the case of iron chloride that we learned about in class today, the end result is the same, because due to iron's strong positive charge the species that bind to iron eventually give off a proton anyway. However, since iron chloride does not directly give off a proton it cannot be called a Bronsted acid even though it still has the same effect of lowering the pH.


Thank you! Does this mean that the different definitions are just adapted because some acids don't fit one definition? Like one acid doesn't fit the def of a bronsted acid but it still is an acid so it's classified as another type of acid?


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