What factors affect the boiling point of polar molecules?

AI Thread Summary
The boiling points of methoxymethane, butane, pentane, and water are debated, with initial assumptions placing butane lower than pentane and methoxymethane. However, the correct order is methoxymethane < butane < pentane < water. Methoxymethane, despite being polar, has a lower boiling point due to its weak dipole-dipole interactions and hydrophobic interactions in longer alkanes, which are stronger. Ethers like methoxymethane are generally nonpolar and have boiling points similar to alkanes of comparable molecular mass. The discussion highlights that while polarization affects boiling points, molecular size and hydrophobic interactions often play a more significant role, as seen in the comparison of carbon monoxide and nitrogen, which have similar boiling points despite differing polarities.
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arrange the boiling point of the following compounds
methoxymethane,butane,pentane and water
I quickly arrange like this
butane<pentane<methoxymethane<water
but after checking wiki,it should be
methoxymethane<butane<pentane<water
In my knowledge,methoxymethane is a polar molecule,so i should have a higher boiling point
Why,that it's not make sense?
Also which of the following has the higher priority when we are considering the boiling point, the polarization or the molecular size?
thanks!
 
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The ether is only slightly polar, so the hydrophobic interactions of the longer alkenes are stronger.
 
in general ethers can be regarded as basically nonpolar and have boiling points comparable to alkanes of similar molecular mass.

indeed have you noticed that the dipole-dipole interaction is extremely weak and doesn't really matter (in terms of phase change temperatures) in many cases, with only hydrogen bonding significantly altering the boiling point?

Carbon monoxide is isoelectronic with nitrogen N2, has the same mass, is much more polar than N2 yet they boil at almost the same temperature: 82 K vs. 78 K.

However, the dielectric properties of polar molecules are going to be different.
 
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