Biology/Chemistry: pH Level and Ionizable Groups

[Soaring Crane]

Homework Statement

Select any molecule [from the assigned chapter] that has more than 2 ionizable groups. Write its structures, showing every atom, at pH levels 1 and 7.

Homework Equations

See below.

The Attempt at a Solution

http://en.wikipedia.org/wiki/Geranyl_pyrophosphate

The molecule that I chose is geranyl pyrophosphate:


____________________________________O_____O
____________________________________||____||
CH3C(CH3)=CHCH2CH2C(CH3)=CHCH2--O—P--O--P--O-
____________________________________|_____|
____________________________________O-____O-

This one does have 3 ionizable groups, right?

At pH 1, the molecule is under acidic conditions, so will all the ionizable groups be protonated?

____________________________________O_____O
____________________________________||____||
CH3C(CH3)=CHCH2CH2C(CH3)=CHCH2--O--P--O--P--OH
____________________________________|_____|
____________________________________OH____OH


At pH = 7, the presence of water can be presumed(?), so does this arise?


____________________________________O
____________________________________||
CH3C(CH3)=CHCH2CH2C(CH3)=CHCH2--O—P--OH
____________________________________|
____________________________________O-

+ __O
____||
HO--P--O-
____|
____O-


Thanks.

 

[Soaring Crane]

Revision here.

At pH 1, will all the groups be protonated like so?

____________________________________O_____O
____________________________________||____||
CH3C(CH3)=CHCH2CH2C(CH3)=CHCH2--O--P--O--P--OH
____________________________________|_____|
____________________________________OH____OH


At pH 7, will all the groups be unprotonated like so?

____________________________________O_____O
____________________________________||____||
CH3C(CH3)=CHCH2CH2C(CH3)=CHCH2--O—P--O--P--O-
____________________________________|_____|
____________________________________O-____O-

Or must I treat this like a triprotic acid in which each group is protonated at various instances? (If so, how do I go about doing this?)

Thank you.

 

[Blueshift5]

I would like to commend you on your choice of molecule and your attempt at finding its structures at different pH levels. Geranyl pyrophosphate does indeed have three ionizable groups, as indicated by the presence of three phosphates in its structure.

At pH 1, all three ionizable groups would indeed be protonated, as you have shown in your structure. This is because at such a low pH, the solution is highly acidic and has a high concentration of H+ ions, which would protonate the ionizable groups.

At pH 7, the solution is neutral and has a lower concentration of H+ ions. In this case, only one of the ionizable groups would be protonated, as shown in your structure. The other two groups would remain deprotonated, as they are not acidic enough to be protonated at this pH.

Your attempt at showing the structures at different pH levels is a good start, but as a scientist, I would also like to point out that the actual structures may be more complex due to the presence of water molecules and other ions in solution. In addition, the protonation of ionizable groups may also affect the overall conformation and stability of the molecule. Therefore, further research and experimentation would be needed to fully understand the behavior of geranyl pyrophosphate at different pH levels.