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Shapes of molecules

Please could someone explain how the shape of molecules influence the intermolecular forces that affect melting point (is it to do with lone pairs?)
Reply 1
Avatar for scimus63
scimus63
9
one of the main factors that affect inter molecular bonding is the surface area or contact area between molecules. Obviously if the molecules have small areas of contact there is little prospect of lots of intermolecular bonding, this is where the shape comes into it!
If you draw out two molecules of n-pentane with one above the other, then draw out 2 molecules of 2,2-dimethyl propane, an isomer of n-pentane, there will be a larger area of contact with the n-pentane and not much with its isomer. This will allow more inter molecular bonding to take place, enough to change the boiling and melting points of these two substances even tho they have the same formula.
Reply 2
Avatar for Seahorse03
Seahorse03
OP
7
Original post by scimus63
one of the main factors that affect inter molecular bonding is the surface area or contact area between molecules. Obviously if the molecules have small areas of contact there is little prospect of lots of intermolecular bonding, this is where the shape comes into it!
If you draw out two molecules of n-pentane with one above the other, then draw out 2 molecules of 2,2-dimethyl propane, an isomer of n-pentane, there will be a larger area of contact with the n-pentane and not much with its isomer. This will allow more inter molecular bonding to take place, enough to change the boiling and melting points of these two substances even tho they have the same formula.

Thank you so much for your help!

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