[schafer]

Hey,

I cam across this question:
"Which of the following functional groups normally acts as an acid?"

According to what I checked, the correct answer is phosphate and carboxyl, since they can give away an hydrogen proton.

My question is, why aren't other groups, such as hydroxyl or amino, considered acid? They also have hydrogen atoms which they can 'give'.

Thanks, and sorry for any mistakes I did with my English (not native language)

[Hunter2]

It is considered together with water. Amines attract hydrogen from water so it acts as a base. Hydroxyl is to weak in coresponding to water, If it is an alcohol, phenoles instead are acidic.
Beside the carboxyl and phosphate there is some more like sulfonate, phenolate, etc. which acts as an acid.