[ifuller]

Hello,
I have been doing some experimentation using acids. I know how well each acid does in my experiments but am having trouble determining what the "good" acids have in common that the others do not. Can anyone help me find similarities between these acids? I have already ruled out acidity and solubility as possible similarities. The four acids I have been using, in order of effectiveness are:
Ascorbic Acid
Citric Acid
Succinic Acid
Tartaric Acid
Thank you for anyone who can help.

[enahs]

What do you mean by "good"? And order of effectiveness, effectiveness of doing what?

Are you asking which is the strongest acid and which is the weakest?

[profmsg]

i strongly agree with "enahs".
provide more information on what you are looking for>>

what experiment you are doing?--differet acids are good for different experiment.

what do you meaning of good? if acidity and solubility then varies with different solvents.

what do you mean similarities..

clarify more

[ifuller]

I apologize for the lack of clarity. Basically, I have been doing experimentation using acids as reaction accelerators. The "good" quality means that that particular acid accelerates the reaction more than the lower quality acids. I am thinking that there has to be some quality that the "good" acids have that the lower rated acids do not. I am trying to optimize my system by finding the most effective acidic accelerator., Thanks again

[Borek]

Give some more info - what kind of reaction?

[ifuller]

I am using the acids as accelerators in place of rare, precious metal catalysts for metal or chemical hydrides. These acids increase the hydrogen production rate as well as the final hydrogen yield. The better acids offer higher hydrogen production speeds than those of the other acids. I have already ruled out the acidity and the solubility as reasons that some acids work better than others. Any other ideas?

[Borek]

What about - all acids mentioned are complexing agents?

[ifuller]

The first two acids, Ascorbic Acid and Citric Acid, work very well in my experiments. ie. They accelerate the reaction very well. The other two however, Succinic Acid and Tartaric Acid do not work as well. I am trying to find the acid that accelerates the reaction the most. In order to do this, I am trying to find some similarities between the two that work that the two that don't work don't have. I know this is hard to understand and I apologize for not being able to write it more clearly. Thank you again

[ifuller]

In case it helps anyone, Oxalic Acid also works very well at accelerating the reaction. Thanks

[lemonoman]

I would recommend doing a bit of molecular modelling to figure out exactly how each of those works as a catalyst.  Seeing the reaction happen as a movie might help you visualize why some acids work and some don't.

It could probably be done pretty quickly, I doubt you need a huge amount of accuracy.

[ifuller]

Thank you for the help. What exactly do you mean by molecular modeling?

[lemonoman]

There are computer programs that will use the math of intermolecular forces to help you find the lowest energy state for a system, or the lowest energy transition state for a reaction.  It takes a bit of getting used to, but chances are someone at your institution has experience with one of them (like Gaussian).

I suggest that only because the system you seem to be modelling is relatively small...although I guess I never thought about where the H2 is coming from.  It's really a more physical-chemistry approach, and may not be worth your time, especially if you can just test different acids and find similarities the old-fashioned way.