Blind Angel - 30-4-2003 at 08:41
NaOH is a base
HCl is an acid
HCOOH is an acid
BzOH is an acid (?)
CH<sub>3</sub>OH is an alcool
What the difference in a phenol -OH, alcool -OH and a base -OH and carboxylic acid -OH?
Why some are base, why some are acid and the other are nothing?
I am a fish - 30-4-2003 at 09:55
According to the Brønsted Lowry theory of acids and bases:
An acid is a proton (H+ ion) donor.
A base is a proton acceptor.
For a molecule to be acidic, its conjugate base (the molecule that remains when a proton has been given) must be stable. Although methane contains
hydrogen, it isn't an acid, because its conjugate base (CH3 -) is extremely unstable. Similarly, methanol is not acidic as its conjugate base
(CH3O -) is unstable (this is not strictly true - it can act as an acid in the presense of a very strong base such as metallic sodium). Methanoic
acid and phenol are weak acids as their conjugate bases (HCOO -, BzO -) are fairly stable as the negative charge is spread over the molecule. HCl is
a strong acid as its conjugate base (the chloride ion) is very stable.
NaOH is a base, as the the OH- ion is a good proton acceptor. To put this another way, the conjugate acid (the molecule that results from accepting a
proton) of the OH - ion (namely water) is stable.
Chris
Blind Angel - 30-4-2003 at 12:16
Thanx, that explain all, i finally got a better answer than: -OH is a base exept when in organic compound and H- is an acid from my teacher...
a123x - 30-4-2003 at 12:29
Remember though that the hydrogen only makes it an acid when its H+ otherwise NH3 would be an acid when in reality its a base.
madscientist - 30-4-2003 at 12:37
Inorganic compounds with OH are not always bases. For example, aluminum hydroxide can be both an acid and a base.
Darkfire - 30-4-2003 at 14:33
The -oh group in an alchohal(SP) is covalantly bonded to another atom. The oh group in a hydroxide is only an ionib bond, thus it easliy gain one h+.
CTR