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Why does boron trifluoride (BF3) act as a Lewis base and ammonia (NH3) acts as a Lewis acid?
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Mrs.Brie Zee.2U
Why does boron trifluoride (BF3) act as a Lewis base and ammonia (NH3) acts as a Lewis acid?
Q. Why does boron trifluoride (BF3) act as a Lewis base and ammonia (NH3) acts as a Lewis acid?
The premise of your question is flatly wrong.
[math]mathrm{BF_3}[/math] is a strong Lewis acid, as boron is inherently electron-deficient. Boron has only three valence electrons, so even if it uses all of them in electron-pair bonds, it only has six of the eight electrons needed for an octet.
And, in fact, [math]mathrm{BF_3}[/math] is commonly used as a Lewis acid — for example, in transesterification reactions using alkoxide nucleophiles, so that one can have an acid and a base in the same reaction mixture.
Meanwhile, [math]mathrm{NH_3}[/math] is a Lewis base. Nitrogen has five valence electrons, which means that when it obtains an octet by forming three electron-pair bonds, there is a non-bonded pair of electrons (“lone pair”) remaining that can be donated to Lewis acids — such as [math]mathrm{BF_3}[/math].
Q. Why does boron trifluoride (BF3) act as a Lewis base and ammonia (NH3) acts as a Lewis acid?
The premise of your question is flatly wrong.
[math]mathrm{BF_3}[/math] is a strong Lewis acid, as boron is inherently electron-deficient. Boron has only three valence electrons, so even if it uses all of them in electron-pair bonds, it only has six of the eight electrons needed for an octet.
And, in fact, [math]mathrm{BF_3}[/math] is commonly used as a Lewis acid — for example, in transesterification reactions using alkoxide nucleophiles, so that one can have an acid and a base in the same reaction mixture.
Meanwhile, [math]mathrm{NH_3}[/math] is a Lewis base. Nitrogen has five valence electrons, which means that when it obtains an octet by forming three electron-pair bonds, there is a non-bonded pair of electrons (“lone pair”) remaining that can be donated to Lewis acids — such as [math]mathrm{BF_3}[/math].
Q. Why does boron trifluoride (BF3) act as a Lewis base and ammonia (NH3) acts as a Lewis acid?
The premise of your question is flatly wrong.
[math]mathrm{BF_3}[/math] is a strong Lewis acid, as boron is inherently electron-deficient. Boron has only three valence electrons, so even if it uses all of them in electron-pair bonds, it only has six of the eight electrons needed for an octet.
And, in fact, [math]mathrm{BF_3}[/math] is commonly used as a Lewis acid — for example, in transesterification reactions using alkoxide nucleophiles, so that one can have an acid and a base in the same reaction mixture.
Meanwhile, [math]mathrm{NH_3}[/math] is a Lewis base. Nitrogen has five valence electrons, which means that when it obtains an octet by forming three electron-pair bonds, there is a non-bonded pair of electrons (“lone pair”) remaining that can be donated to Lewis acids — such as [math]mathrm{BF_3}[/math].
For more, see the material on Lewis acids and bases in LibreTexts.
Q. Why does boron trifluoride (BF3) act as a Lewis base and ammonia (NH3) acts as a Lewis acid?
The premise of your question is flatly wrong.
[math]mathrm{BF_3}[/math] is a strong Lewis acid, as boron is inherently electron-deficient. Boron has only three valence electrons, so even if it uses all of them in electron-pair bonds, it only has six of the eight electrons needed for an octet.
And, in fact, [math]mathrm{BF_3}[/math] is commonly used as a Lewis acid — for example, in transesterification reactions using alkoxide nucleophiles, so that one can have an acid and a base in the same reaction mixture.
Meanwhile, [math]mathrm{NH_3}[/math] is a Lewis base. Nitrogen has five valence electrons, which means that when it obtains an octet by forming three electron-pair bonds, there is a non-bonded pair of electrons (“lone pair”) remaining that can be donated to Lewis acids — such as [math]mathrm{BF_3}[/math].
For more, see the material on Lewis acids and bases in LibreTexts.
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You’ve got it backwards.
Ammonia has one lone pair of electrons. Ammonia is an electron pair donor, and thus a Lewis base.
Boron has only three bonding pairs of electrons in BF3. Boron trifluoide is an electron pair acceptor, and thus a Lewis acid.
You’ve got it backwards.
Ammonia has one lone pair of electrons. Ammonia is an electron pair donor, and thus a Lewis base.
Boron has only three bonding pairs of electrons in BF3. Boron trifluoide is an electron pair acceptor, and thus a Lewis acid.
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