Greetings,
It's been a while, but I'm back. For this post we turn our attention toward properties of aldehydes, with an emphasis on water solubility and boiling points. The three lowest molar mass aldehydes are all quite soluble in water because of the relative high strengths of their molecular dipole moments. This means that the dipole-H bonding forces between the aldehyde and water molecules are strong. The dipole-H bonding forces drops off somewhat for propionaldehyde, and so we see a limit of solubility in water (compared to formaldehyde and acetaldehyde).
The boiling points of pure aldehydes increase with increasing molar mass because the extent of all intermolecular forces (London Dispersion plus Dipole-Dipole) increases with increasing molecular size. The graphic image below provides a summary.
Please note: The molecular model views are animated. To see this animation, simply open the image in a new tab.
One can see from the illustration that there is a limit for propionaldehyde solubility in water. This is due to a weakening of the molecular dipole moment because of the "electron adding" effect of the growing carbon chain. The weaker dipole moment decreases the strength of polar intermolecular attractions with water and we see the solubility decreasing, as a result.
That's all for now. As always, thank you for reading.
A Publication of http://ExcellenceInLearning.biz
It's been a while, but I'm back. For this post we turn our attention toward properties of aldehydes, with an emphasis on water solubility and boiling points. The three lowest molar mass aldehydes are all quite soluble in water because of the relative high strengths of their molecular dipole moments. This means that the dipole-H bonding forces between the aldehyde and water molecules are strong. The dipole-H bonding forces drops off somewhat for propionaldehyde, and so we see a limit of solubility in water (compared to formaldehyde and acetaldehyde).
The boiling points of pure aldehydes increase with increasing molar mass because the extent of all intermolecular forces (London Dispersion plus Dipole-Dipole) increases with increasing molecular size. The graphic image below provides a summary.
Please note: The molecular model views are animated. To see this animation, simply open the image in a new tab.
One can see from the illustration that there is a limit for propionaldehyde solubility in water. This is due to a weakening of the molecular dipole moment because of the "electron adding" effect of the growing carbon chain. The weaker dipole moment decreases the strength of polar intermolecular attractions with water and we see the solubility decreasing, as a result.
That's all for now. As always, thank you for reading.
A Publication of http://ExcellenceInLearning.biz
No comments:
Post a Comment
Comments or Questions? Feedback is always welcome!