Boiling Points

[StarlingForce1]

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From Kaplan:

"Physical properties of alkenes are similar to those of alkanes, for example, the B.P. and M.P. increase with increasing molecular weight and are even similar in value to those of corresponding alkanes."

So, values are similar, but ultimately, are the MP and BP higher or lower than the corresponding alkane? I realize cis/trans isomers must be taken into account, but for now, consider the non substituted ethene vs. ethane. Higher or lower?

Thanks!

🙂

 

[blueshockey]

MP and BP will be lower. First of all, the melting point. It will be lower in an alkene because due to the kinks that the double bond induces in the chain, it will not be able to pack as efficiently (not as many intermolecular forces). By the same logic, the boiling point of the alkene should also be lower.