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bonding

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bonding

Postby mercuryy » Tue Oct 10, 2006 10:09 pm

what aspect of hexine's gemoetry makes the intramolecular carbon-Hydrogen bond effective and how do the overall shape of the molecules change by the introduction of carbon-carbon double bond? I think they become more linear like, right but why?
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Postby mith » Wed Oct 11, 2006 2:18 pm

double bonds are stronger than singles, and don't allow rotations.
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Postby mercuryy » Sat Oct 14, 2006 7:21 pm

i thought single bond is stronger than double. isn't it less reactive? and is there specific name given for the shape of moleucles such as ethane and hexane?
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Postby mith » Sat Oct 14, 2006 9:42 pm

no, a double bond has almost double the strength of a single and holds the two atoms closer together...I don't know what you mean by reactive.
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Postby mercuryy » Sat Oct 14, 2006 10:55 pm

isn't it true that double bond is more reactive than single bond because it is unsaturated? bond in unsaturated hydrocarbon can be break more easily than saturated hydrocarbon
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Postby victor » Sun Oct 15, 2006 4:02 am

Well, I think you have to differ between bond strength and reactivity. Bond strength is measured in kkal/mole or kJ/mole, means that the presence of energy which is enough to break the bond. And yes, double bond is stronger that the single one (the bond strength is nearly twice as much that single).

Now, let's move to reactivity. You said that double bond is more reactive which is proven in unsaturated TAG (triacylglycerol) that is easily oxidized. This is true, but just in the term of electrophilic addition and free radical addition.

Double bond is composed of one sigma-bond and another pi-bond. the sigma-bond is composed by electron share by each atom, while pi-bond is composed by two electron orbital which stand in a row. The reactivity of double bond is due to the existence of this pi-bond, since it's located at the outer area compared to sigma bond.

One thing that you've to remember, covalent bond is made by electron sharing systems, so pi-bond is also made by this system thus, it has a negative charge and will be attracted to positive charge (electrophilic atom/molecule). And this attraction is what you mean by more reactive...:D

So, the conclusion is, the reactivity of one substance is depend on the reaction and bond strength only determine the speed of the reaction.

Hope this helps,
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