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Author Topic: Why do alkanes with even numbers of carbon atoms pack more closely?  (Read 8054 times)

Offline EvilFrog

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why alkanes with even number of carbon atoms packed more closely in solid state and have higher melting and boiling points?
« Last Edit: 04/09/2009 17:20:32 by chris »


 

Offline Nizzle

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Phew, organic chemistry was never my strong suit, but here's what i think:

Because alkanes can rotate aroud their C-C single bonds, but alkenes can't rotate around there C=C double bonds.
 

Offline EvilFrog

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Why alkane with odd number of carbon atoms packed less closely than alkane with even number of carbon atom?
 

Offline johnson039

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chemistry text books tell us even no. alkanes are more symmetric than odd no alkanes, so they pack more closely and hence melting points are higher.
 

Offline EvilFrog

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"If the double bond is stronger than the single bond, why alkenes are more reactive than alkanes?

When reagents add across the double bond in ethene, the pi bond is broken, this require energy. The energy used in breaking the one pi bond, however, is more than repaid by the energy released when two new bond are made.

Hence, alkenes are energetically unstable relative to their products in an addition reaction. They are also kinetically unstable, because the high electron density in the double bond tends to attract electrophiles, thus initiating addition reactions. "


The statement above is what my lecture tell me. But I can't understand it.

What is energically unstable and kinetically unstable? ???
 

Offline EvilFrog

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what is energetically unstable and kinetically unstable????
 

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