Millymoo24
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I’m stuck on a hwk question and there doesn’t seem to be anything in the textbook/my notes to help

Aminoethanoic acid (glycine), NH2CH2COOH, is an amino acid. It is found in fish, meat, beans, and dairy produce. It can behave both as an acid and as a base.

Explain why aminoethanoic acid behaves as:

1) an acid when it reacts with sodium hydroxide

2) a base when it reacts with hydrochloride acid

Any help is much appreciated 😁
Last edited by Millymoo24; 2 months ago
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viol.aaa
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Hi, this page might help you!
https://www.chemguide.co.uk/organicp.../acidbase.html

Amino acids can act as both acids and bases, depending on what solution they are in. They have an NH2 group and COOH group. If you read this article the question should make more sense.
Hope it helps
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Millymoo24
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(Original post by viol.aaa)
Hi, this page might help you!
https://www.chemguide.co.uk/organicp.../acidbase.html


Amino acids can act as both acids and bases, depending on what solution they are in. They have an NH2 group and COOH group. If you read this article the question should make more sense.
Hope it helps
Yes this was really helpful thanks

Just to double check, the answer to (1) would be that the COOH group has lost a H atom, and (2) would be that the NH2 group has gained a H atom?
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viol.aaa
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(Original post by Millymoo24)
Yes this was really helpful thanks

Just to double check, the answer to (1) would be that the COOH group has lost a H atom, and (2) would be that the NH2 group has gained a H atom?
I think in a neutral solution, amino ions exist as Zwitterions so usually have NH3+ and COO- groups instead.
But in (1) when it’s in a basic solution, it acts like an acid, so loses a hydrogen from its NH3+ group. This leaves it with NH2 and COO-
Then in (2) when it’s in acidic solution, it acts like a base, so it gains a hydrogen on its COO- group, forming COOH. This leaves it with NH3+ and COOH
I’ve probably explained it really badly as I’m in A2 chem as well so I’m not an expert on this tbh 😂
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Millymoo24
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(Original post by viol.aaa)
I think in a neutral solution, amino ions exist as Zwitterions so usually have NH3+ and COO- groups instead.
But in (1) when it’s in a basic solution, it acts like an acid, so loses a hydrogen from its NH3+ group. This leaves it with NH2 and COO-
Then in (2) when it’s in acidic solution, it acts like a base, so it gains a hydrogen on its COO- group, forming COOH. This leaves it with NH3+ and COOH
I’ve probably explained it really badly as I’m in A2 chem as well so I’m not an expert on this tbh 😂
ahh that makes sense we haven’t been taught any of this 😂 I think I just got them the wrong way around, thank you!
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hayydenb
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Also, by the Bronsted-Lowry definitions of acids and bases, acids donate protons (H+) and bases accept protons (H+). Hope this also helps
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Millymoo24
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(Original post by hayydenb)
Also, by the Bronsted-Lowry definitions of acids and bases, acids donate protons (H+) and bases accept protons (H+). Hope this also helps
Yes that’s amazing, thank you!
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