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Topic: acidity  (Read 3457 times)

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Offline orgoclear

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acidity
« on: May 08, 2009, 01:57:20 AM »
Wikipedia says that:
Methanol is more acidic than water. (indirectly though by mentioning pKa values)
pKa of methanol = 15.5
pKa of water = 15.74

I cant find a satisfactory reason to this considering that all other aliphatic alcohols are less acidic than water

Offline singh.abhijitpratap

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Re: acidity
« Reply #1 on: May 10, 2009, 06:15:39 AM »
it's absolutely true that methanol is more acidic than water.in chemistry or any other science we execute experiments and then come to conclusions and then propose an explanation,it's not the reverse.the apparent justification given to this phenomena is that since the charge density on the methoxide ion is higher than hydroxyl, so it's slightly more solvated and hence stabilized,hence making methanol more,just slightly more acidic than water.the steric hindrance of both the molecules is nearly the same and hence that factor does not count.Even i didn't digest this at the beginning but we cannot expect everything to go by theory.We have to face few exceptions like this.

Offline Arkcon

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Re: acidity
« Reply #2 on: May 10, 2009, 09:37:39 AM »
You can try to understand it backwards as well -- water is a stronger base, than methanol.  Since we define pH, as the activity of H+, and define pure water as neutral, pH 7.0, you can see that methanol is more likely to donate a proton, than to donate an hydroxyl, if you want to look at it that way.  'Tho I am mixing up definitions shamelessly here. ;D
Hey, I'm not judging.  I just like to shoot straight.  I'm a man of science.

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