Organic chemistry boiling point

In summary, the question is asking whether the boiling point of propanoic acid is less than that of n-butyl alcohol, given that they have similar molecular weights. The two potential explanations are the presence of hydrogen bonding in propanoic acid and the formation of dimers in its liquid state. After discussing the properties of carboxylic acids and the effects of hydrogen bonding, it is determined that the correct explanation is the dimerization of propanoic acid, leading to weaker interactions between the dimers and a lower boiling point. The presence of water is also briefly mentioned, but ultimately dismissed as irrelevant to the question.
  • #1
erisedk
374
7

Homework Statement


State true or false:
The boiling point of propanoic acid is less than that of n-butyl alcohol, an alcohol of comparable molecular weight.

Homework Equations

The Attempt at a Solution


Is this just a question where you either know it or don't OR is there some argument based off hydrogen bonding and the like that you can give?
 
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  • #2
erisedk said:
is there some argument based off hydrogen bonding

Try to think of one.
 
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  • #3
There's hydrogen bonding in both, but because of two O atoms there is more hydrogen bonding in propanoic acid? And therefore the boiling point of propanoic acid should be more?
 
  • #4
Propanoic acid is a carboxylic acid with a COOH group, so, a property of carboxylic acids in liquid state is?
Formation of ___?
If you get that, then you can easily answer your question.
 
  • #5
They dimerise!
But the answer would then be true. However, if I consider greater hydrogen bonding with water, like I previously stated, the answer would be false. Which is the right explanation?
 
Last edited:
  • #6
erisedk said:
They dimerise!
But the answer would then be true.
How did you come to that conclusion?
 
  • #7
erisedk said:
However, if I consider greater hydrogen bonding with water, like I previously stated,
May I know Why exactly you are bringing water into the conversation?
 
  • #8
Suraj M said:
How did you come to that conclusion?

Because if they dimerise, then between two dimers there are only van der waal interactions (because this is like intramolecular hydrogen bonding, which is why ortho nitrophenol is steam volatile). Since there are very weak interactions between different dimerised pairs, the boiling point of the liquid is less.

Suraj M said:
May I know Why exactly you are bringing water into the conversation?
Sorry, no water. Just this: There's hydrogen bonding in both, but because of two O atoms there is more hydrogen bonding in propanoic acid? And therefore the boiling point of propanoic acid should be more?
 
  • #9
If you draw the diner structure you'll see that though there are hydrogen bonds within the diner the oxygen can still make more hydrogen bonds and when you say boil you'll have to separate the constituents of the dimer also, so you have to consider the interaction between them,
Okay so I think you get the idea
Yes propanoic acid has a higher BP
 
  • #10
OK thanks!
 

What is the definition of boiling point in organic chemistry?

The boiling point in organic chemistry refers to the temperature at which a liquid substance changes state from a liquid to a gas. It is also known as the boiling temperature.

How does the structure of a molecule affect its boiling point in organic chemistry?

The structure of a molecule can greatly affect its boiling point in organic chemistry. Generally, molecules with stronger intermolecular forces, such as hydrogen bonding or dipole-dipole interactions, will have higher boiling points. This is because more energy is required to break these intermolecular forces and overcome the attractive forces between molecules.

What are the factors that can influence the boiling point of a compound in organic chemistry?

Aside from the structure of a molecule, other factors that can influence the boiling point of a compound in organic chemistry include the size and shape of the molecule, as well as the presence of functional groups. The strength of intermolecular forces, the polarity of the molecule, and the surrounding pressure can also play a role in determining the boiling point.

How can the boiling point of a compound be determined in organic chemistry?

The boiling point of a compound can be determined through various methods, such as distillation or using a boiling point apparatus. It can also be predicted by analyzing the molecular structure and intermolecular forces present in the compound.

Why is knowing the boiling point important in organic chemistry?

The boiling point is an important physical property of a compound as it can provide information about its intermolecular forces, molecular structure, and purity. It can also be used for the separation and purification of compounds through techniques like distillation. Additionally, it can aid in the identification and characterization of unknown compounds.

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