Melting Points trend for Primary Alcohols

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SUMMARY

The discussion centers on the melting point trends of primary alcohols, highlighting that melting points do not consistently increase with molecular weight due to the influence of molecular structure. Specifically, branching in isomers reduces the points of contact between molecules, leading to decreased van der Waals forces and lower melting points. Straight-chain isomers exhibit higher melting points due to increased intermolecular interactions. Additionally, the polarity of certain isomers, such as cis and trans configurations, further affects melting points.

PREREQUISITES
  • Understanding of molecular weight and its impact on physical properties
  • Knowledge of isomerism, particularly structural and geometric isomers
  • Familiarity with intermolecular forces, specifically van der Waals forces
  • Basic concepts of polarity in organic molecules
NEXT STEPS
  • Research the impact of molecular structure on melting points in organic chemistry
  • Study the differences between cis and trans isomers and their physical properties
  • Explore the role of branching in hydrocarbons and its effect on melting points
  • Learn about van der Waals forces and their significance in molecular interactions
USEFUL FOR

Chemistry students, organic chemists, and anyone interested in the physical properties of organic compounds, particularly those studying melting point trends in alcohols and other organic molecules.

LadiesMan
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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
 
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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...
 

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