[lespaul]

Ok, so I know this sounds crazy, but can sucrose act as an acid in water?

My reason for stating this is as follows:

1. The pKa of sucrose is 12.62, since water has a pKa of 14 (STP) it can "pull off" the H+ from the many OH groups on the sugar molecule. Once H+ are free and into solution it can cause a change in pH.

2. Even if one individual H+ (from oH) did NOT contribute much to pH, remember that sugar is very polar and has a total of 8 hydroxyl groups in its structure - thereby contributing significantly when taken as a whole.

Again, I know this sounds crazy and is completely wrong - but why?


Even other sugars - fructose (pKa=12.06 @18C), glucose (pKa=12.92) have pKas listed.


What purpose then does stating the pKa for sucrose have? (in terms of acidity/basicity)

References:

pKa data from: http://sis.nlm.nih.gov/chemical.html
Other info: http://en.wikipedia.org/wiki/Sucrose

[Arctic-Nation]

Have you ever heard about the autoionisation of water? Do you even know the pH of water?

The pKa of water is 15.7, but what you need is the pKa of the hydronium ion, H3O+, which would be created in your hypothetical protolysis. That pKa is -1.7. Now think again.