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Topic: About the bonds of SO3!  (Read 19207 times)

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Offline Winga

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About the bonds of SO3!
« on: November 24, 2004, 11:53:34 PM »
Some books said SO3 has three S=O double bonds; some said it has three S-O dative covalent bonds; and some said it has two S=O double bonds & one S-O dative covalent bond.

Which one is correct?  

Offline AWK

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Re:About the bonds of SO3!
« Reply #1 on: November 25, 2004, 01:59:41 AM »
Sulfur belongs to the third period and for it the octet rule should not be fulfilled,
but formally it is fulfilled in the case of one double bond and two dative covalent bonds.
As a teacher I prefer this method, and accept three double bonds, but not the other possibilities presented by you.
The octet rule is absolutely required for the second period.
« Last Edit: November 25, 2004, 02:01:00 AM by AWK »
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Offline Winga

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Re:About the bonds of SO3!
« Reply #2 on: November 25, 2004, 07:11:10 AM »
How about drawing the mechanism of sulfonation of benzene?

I saw the book, whcih using 3 S=O double bonds. So, can I draw the mechanism by using one double bond and two dative covalent bonds?

Offline Donaldson Tan

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Re:About the bonds of SO3!
« Reply #3 on: November 25, 2004, 05:30:25 PM »
actually, in virtue of electron delocalisation, all three structures suggested are actually cannonical structures. SO3 exhibits reasonance, whereby its actual structure is in between these 3. ie. the bond order each S-O bond is actually 1.5.
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Offline Mitch

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Re:About the bonds of SO3!
« Reply #4 on: November 25, 2004, 08:50:34 PM »
you mean 1.666?
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Offline AWK

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Re:About the bonds of SO3!
« Reply #5 on: November 26, 2004, 01:08:25 AM »
Draw the mechanism according to scheme of electrophilic aromatic substitution:
1. pi-complex
2. sigma complex
3. H(+) shift
« Last Edit: November 26, 2004, 03:19:59 AM by AWK »
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Offline Winga

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Re:About the bonds of SO3!
« Reply #6 on: November 26, 2004, 02:16:39 AM »
you mean 1.666?
Is it 6 e- shared by 4 atoms? 1.5?

Offline Donaldson Tan

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Re:About the bonds of SO3!
« Reply #7 on: November 26, 2004, 11:46:39 AM »
what exact number is the bond order does not matter. what matters is that sulphur-oxygen bond is somewhat between a single and double bond because of electron delocolisation. the delocalised electrons move readily within the adjacent degenerate molecular orbitals.
"Say you're in a [chemical] plant and there's a snake on the floor. What are you going to do? Call a consultant? Get a meeting together to talk about which color is the snake? Employees should do one thing: walk over there and you step on the friggin� snake." - Jean-Pierre Garnier, CEO of Glaxosmithkline, June 2006

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