[jsmith613]

How does the following reaction demonstrate an amino acid as an acid:
H₂NCH₂COOH + CH₃OH → H₂NCH₂COOCH₃ + H₂O

How does the following reaction demonstrate an amino acid as a base:
H₂NCH₂COOH + CH₃COCl → CH₃CONHCH₂COOH + HCl

An acid is a species that DONATES a proton and a base is a species that ACCEPTS a proton

In both situations it seems more like an esterfication reaction than an acid / base reaction.

Also in the second reaction the H2N loses an H+ for water (I would call that acidic behaviour but it is actually basic behaviour) and the first example COOH loses OH (basic behaviour but is classified as acidic)

I am confused :S

[discodermolide]

How does the following reaction demonstrate an amino acid as an acid:
H₂NCH₂COOH + CH₃OH → H₂NCH₂COOCH₃ + H₂O

How does the following reaction demonstrate an amino acid as a base:
H₂NCH₂COOH + CH₃COCl → CH₃CONHCH₂COOH + HCl

An acid is a species that DONATES a proton and a base is a species that ACCEPTS a proton

In both situations it seems more like an esterfication reaction than an acid / base reaction.

Also in the second reaction the H2N loses an H+ for water (I would call that acidic behaviour but it is actually basic behaviour) and the first example COOH loses OH (basic behaviour but is classified as acidic)

I am confused :S

Simply put, as you have now experimental details:
The acid catalyses it's own esterification /Fischer esterification).
The N-acylation is just the attack of the amino group on an activated carbonyl species.

[jsmith613]

Simply put, as you have now experimental details:
The acid catalyses it's own esterification /Fischer esterification).
The N-acylation is just the attack of the amino group on an activated carbonyl species.

but how in either is the amino acid behaving as an acid / base??

[fledarmus]

What is the reaction mechanism for the two reactions?

Hint: you might want to think about the other definition for acids and bases...

[jsmith613]

What is the reaction mechanism for the two reactions?

Hint: you might want to think about the other definition for acids and bases...

In truth I was only aware of two definitions: Arhenius and Bronstred?

[fledarmus]

You haven't come across Lewis acids yet?

[jsmith613]

You haven't come across Lewis acids yet?

no although I think a Lewis acid is an electron acceptor (from other reading)

[Sadi Carnot]

Indeed it is, and a Lewis base is an electron donator

[fledarmus]

Here is a guide giving the mechanisms to the two reactions:

Amide formation from acyl chloride and amine:

http://www.chemguide.co.uk/mechanisms/addelim/amines.html

Ester formation from carboxylic acid and alcohol

http://www.chemguide.co.uk/physical/catalysis/esterify.html

The parts that I think might be of particular significance to your question are highlighted below.

With these pictures and your definition of a Lewis acid (and Sadi's definition of a Lewis base), do you have sufficient information to formulate an answer to your question?