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Reaction of amino acids help needed

qq.pngThis picture shows 2-aminobutanoic acid reacting with excess ethanol with concentrated H2SO4. But I have a few questions about the answer. First, why is the amine group not protonated since acid is present, why is NH3+ not formed? Second, I don't get how 2 water molecules are produced.

This is another example I found to support my point.

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Reply 1
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coconut64
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Also I am guessing the positive charge is on N right?
Reply 2
Avatar for Pigster
Pigster
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You're right.

The only justification I can think of for the first image is: if you acid catalyse the esterification, you'll make the protonated amino version as in the second image with the creation of 1x H2O (and yes the + is on the N). If you then neutralise, by adding OH-, you'll generate a second H2O. Perhaps the first image shows the overall equation, without making reference to the work-up stage or including the reagents, but whilst still including one of the products in the equation.

Taking the equation as written, it is clearly not balanced, so some information must be missing.
Reply 3
Avatar for coconut64
coconut64
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Original post by Pigster
You're right.

The only justification I can think of for the first image is: if you acid catalyse the esterification, you'll make the protonated amino version as in the second image with the creation of 1x H2O (and yes the + is on the N). If you then neutralise, by adding OH-, you'll generate a second H2O. Perhaps the first image shows the overall equation, without making reference to the work-up stage or including the reagents, but whilst still including one of the products in the equation.

Taking the equation as written, it is clearly not balanced, so some information must be missing.


That's all I am given in the question, so only 1 water molecule should be produced?
Reply 4
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Pigster
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Original post by coconut64
That's all I am given in the question, so only 1 water molecule should be produced?


Agreed.
Reply 5
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coconut64
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Original post by Pigster
Agreed.


Also, it should be NH3+? Just double checking . cheers
Reply 6
Avatar for Pigster
Pigster
20
Original post by coconut64
Also, it should be NH3+? Just double checking . cheers


It depending on the wording of the Q.

The product of the acid catalysed esterification reaction involving those reagents IS the protonated version you think it should be.

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