Can NH2 with no formal charge on it be protonated?

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In summary, the NH2 group on the benzene ring is protonated in the presence of H2O, forming NH4+. The amine is a weaker base than water or phenylether, but is still more basic than them.
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ngu9997
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So I have this question that asks which is the strongest base. I have one structure with a benzene ring with an NH2 group on one side and a methoxy group on another side. Automatically I knew that the NH2 group would be what is protonated in the situation that this structure acts as a base and becomes protonated. But the more I think about it, the less it makes sense. N already has 2 H bonds on it and is attached to the benzene ring and has a lone pair giving it a formal charge of 0. How could it form another H bond in the case it becomes protonated (I assume there has to be some logic as to why the N is what I'm looking at to become protonated rather than the oxygen on the methoxy group).
 
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ngu9997 said:
How could it form another H bond in the case it becomes protonated
How does any amine (or ammonia) get protonated? Just the same.
 
  • #3
Oh wow , I forgot that it was H+ so it wouldn't violate any rules of having more than 8 electrons in N's octet. That makes sense, but how would we determine that the NH2 group gains the hydrogen in protonation rather than the oxygen on the methoxy group?
 
  • #4
ngu9997 said:
Oh wow , I forgot that it was H+ so it wouldn't violate any rules of having more than 8 electrons in N's octet. That makes sense, but how would we determine that the NH2 group gains the hydrogen in protonation rather than the oxygen on the methoxy group?

Because N is usually a stronger base than O.

If you have NH3 and H2O in ammonia water solution and add acid, then you can protonate either water - forming H3O+ - or ammonia - forming NH4+.
But ammonia is much stronger base. H3O+ has pKa of -1,5, while NH4+ has pKa of +9,25.
Now, in aromatic amines, the aromatic ring actually withdraws some of the free electron pair and makes the amine a weaker base. Aniline, C6H5NH3+ has pKa of +4,6.

But it is still much more basic than water, or presumably phenylether.
How does an ether group across the aromatic ring affect pKa of an aromatic amine?
 

Related to Can NH2 with no formal charge on it be protonated?

1. Can NH2 be protonated?

Yes, NH2 can be protonated. Protonation refers to the addition of a proton (H+) to a molecule or ion. As NH2 has a lone pair of electrons, it can readily accept a proton, becoming NH3+

2. Can NH2 with no formal charge on it be protonated?

Yes, NH2 with no formal charge on it can still be protonated. The formal charge of a molecule or ion is the difference between the number of valence electrons and the number of electrons assigned to the atom in the Lewis structure. In the case of NH2, the formal charge is 0, but it can still accept a proton.

3. What is the purpose of protonating NH2?

Protonating NH2 can have various purposes, depending on the specific context. In general, it can alter the chemical and physical properties of the molecule, such as its acidity/basicity, solubility, and reactivity. It can also be used in biological processes, such as in the formation of amino acids in living organisms.

4. How does protonation of NH2 affect its basicity?

Protonation of NH2 increases its basicity. Basicity is a measure of how readily a molecule can accept a proton. As NH2 becomes NH3+ after protonation, it has a positive charge and a greater affinity for a proton, making it a stronger base.

5. Can NH2 with no formal charge on it be deprotonated?

Yes, NH2 with no formal charge on it can be deprotonated. Deprotonation is the loss of a proton from a molecule or ion. NH2 can be deprotonated by a base, resulting in NH- with a negative charge. However, the stability of this deprotonated form depends on the overall molecule and its surroundings.

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