Alkene Hydration in the presence of acid Catalyst.

[jarrod0987]

I am reading The Complete idiots Guide to Organic Chemistry. on page 85 its shows How Acid helps water to bond with Alkene (Propene) in 3 steps

1st step the Pi part of the double bond breaks open in the usual way and steals a proton off the Hydronium forming the Carbocation. Also (And this I might be wrong) looks like the result on the Hydronium is it now turns into regular water which adds up electron wise.

Am I right so far?

2nd step

Now the HOH acts as a lewis base and uses on of its loan pairs to form a coordinated covalent bond with the carbocation. This is where I get lost. If I'm counting my electrons right that should be the end of it.

3rd step

The book says that the water that attached is now + (1 or 2 I don't know) and now it grabs some electrons from another water but then still gives up a proton to it to form another hydronium. I don't understand any of that. Why wasn't it stable on the Carbon and even if it was short an electron or 2, why when it gets them does it still Give up a proton??

[kingchemist]

when water attaches to the carbocation by na coordinate bond, the +ve charge is lost when a proton leaves and an OH group remains.
It is acid catalysis - so proton regenerated

[jarrod0987]

Sorry, I still don't understand. I know what a coordinated bond is but what is a NA coordinated bond?

Heres what I see in my mind. Double boond breaks open and Grabs a spare hydrogen proton off the Hydronium Ion leaving behind Water and a +2 carbocation.

Is this right?

Next comes a normal perfectly stable water which has 2 lone pairs and 2 covalent bonds to hydrogens for a total of 8 valance electrons like normal. It attacks the Carbocation and 1 lone pair becomes shared between the +2 Carbon and the Oxygen as a coordinated bond yes? So now the carbon has the 2 electrons to cancel the +2. It's stable now no longer a cation. Now the oxygen still has those 2 electrons because it is a covalent bond, So it now has 1 covalent bond with carbon and 2 with the hydrogens and 1 lone pair for a total of 8 valance electrons. Its is stable and no charge.

Alas everyone keeps saying it somehow has a +1 charge and so the proton takes off and forces itself onto a water? I Need to understand why the water that attaches to the carbon is + at all. My electron counting says it shouldn't be. Then after that Perhaps I will be able to understand why It gives up a proton to water which would realy like to stay the way it is.

Hope you can clear this up for me. Thank you. Obviously I'm new at this type or chemisty so appreciate your patiance.

[jarrod0987]

ok I went back and reviewed how formal Charges are calculated and found my mistake. I understand now why the charge winds up being +1 on the oxonium and why the Hydrogen proton must go in order to make a formal charge of 0 on the oxygen atom when attached to the carbon. I get that it can just go to another water to make Hydronium again.

I do wonder however, Obviously even though both water and the new organic molucule have all the proper valence electrons and formal charges of 0 , the organic molucule (2 proponol I beleive) is able to overpower the Hydrogen proton and make it leave(I guess by electrostatic repulsion?) and stick to the waters lone pair instead. Why wouldn't the water have the same ability to push it away as water is so stable anyways. What force causes the water to be a larger nucleophile then the new organic molocule formed?? Does it have to do with the shapes somehow?

Hope you can clear up this last little bit.