Melting Points trend for Primary Alcohols

[LadiesMan]

1. What is the trend of melting points for primary alcohols?

I can't understand why melting points dramatically change such as the increase is molecular weight. The melting points doesn't increase nor decrease but they increase and decrease differently when you increase the molecular weight.

Thanks

 

[Kushal]

this may be because of branching... organic molecules do not necessarily exist as straight chain molecules but have different isomers. the more branched the isomers are, the lesser are the points of contact between them. van der waal forces of attraction decreases and melting point also decreases. straight chain isomers have more points of contacts between them, they have a higher melting point.
or some isomers (optical) might be polar and others non polar. you have cis but 2 ene and trans but 2 ene. cis but 2 ene is polar and has a higher melting point.

it does not only occur in alcohols but in many other families of organic molecules...

 

[Blueshift5]

for your question. The trend for melting points in primary alcohols is generally an increase with increasing molecular weight. This is due to the fact that as the molecular weight increases, so does the strength of the intermolecular forces between the alcohol molecules. These forces, such as hydrogen bonding, become stronger with increasing molecular weight, making it more difficult for the molecules to break apart and melt. However, there can be exceptions to this trend due to factors such as branching or other structural differences in the molecules. Overall, the trend of increasing melting points with increasing molecular weight is a result of the increased strength of intermolecular forces in larger molecules.