Melting Points trend for Primary Alcohols

In summary, the trend of melting points for primary alcohols is that they do not consistently increase or decrease with increasing molecular weight. This may be due to branching or the presence of polar isomers. This trend is not specific to alcohols, but is observed in many other families of organic molecules.
  • #1
LadiesMan
96
0
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
 
Physics news on Phys.org
  • #2
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...
 
  • #3
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.
 

1. What is a melting point?

A melting point is the temperature at which a solid substance changes into a liquid state. It is a physical property that is specific to each substance.

2. How is the melting point of primary alcohols determined?

The melting point of primary alcohols can be determined by heating the substance until it melts and recording the temperature at which this occurs. This can be done using specialized equipment such as a melting point apparatus or through visual observation.

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

The trend for melting points of primary alcohols generally increases as the number of carbon atoms in the alcohol chain increases. This is due to the increase in molecular weight and the resulting stronger intermolecular forces.

4. Why do primary alcohols with longer carbon chains have higher melting points?

Primary alcohols with longer carbon chains have higher melting points because they have larger and more complex molecules, which results in stronger intermolecular forces. This makes it more difficult for the molecules to break apart and transition from a solid to a liquid state.

5. Are there any exceptions to the melting point trend for primary alcohols?

Yes, there are some exceptions to the melting point trend for primary alcohols. For example, primary alcohols with branching in their carbon chain may have lower melting points than those with a straight chain due to the reduced surface area for intermolecular interactions. Additionally, the presence of functional groups or other factors can also affect the melting point trend.

Similar threads

  • Biology and Chemistry Homework Help
Replies
2
Views
1K
  • Classical Physics
Replies
3
Views
1K
Replies
9
Views
2K
  • Electromagnetism
Replies
3
Views
758
  • Biology and Chemistry Homework Help
Replies
8
Views
2K
  • Chemistry
Replies
8
Views
3K
  • Biology and Chemistry Homework Help
Replies
5
Views
5K
Replies
19
Views
10K
Back
Top