P roperties
Chemical/Physical Properties
All comparisons are done with the assumption that the compared molecules have similar molar masses
The boiling points for ether are slightly higher when compared to normal hydrocarbons (alkanes, alkenes, etc.) but are lower than alcohols, ketones, and aldehydes. The hydrocarbons have relatively low boiling points due to their structure being non-polar and their intermolecular forces only being weak London Dispersion Forces which makes it require less energy to overcome these forces. Ethers on the other hand have both LDF and (stronger than LDF) Dipole-Dipole intermolecular forces with each other due to the polar ether (-O-) groups on the molecules. These stronger forces is what makes its boiling point relatively high compared to normal hydrocarbons due to the increase in energy needed to overcome the stronger forces. Since alcohols have LDF, dipole-dipole, and stronger hydrogen bonding intermolecular forces due to the hyrdoxyl grouops on the molecule, they have a generally higher boiling point than ethers. Ketones and aldehydes have generally higher boiling points than ethers due to the double bond on the oxygen to carbon bond(s) which cause an increase in polarity for aldehydes and ketones, making their dipole-dipole intermolecular forces significantly stronger when compared to the R-O-R bonds of ethers which have cause the polarity of the molecule to be less than aldehydes and ketones, and a weaker dipole-dipole intermolecular force, which decreases the boiling point (energy needed to break the molecules apart).
The melting point for ethers follows the same trend as the boiling points, the melting points are slighty higher than normal hydrocarbons and lower than alcohols and aldehydes/ketones. ethers have LDF and dipole-dipole intermolecular forces while normal hydrocarbons only have weaker LDF intermolecular forces (which is described in more detail above). The strong dipole-dipole intermolecular forces make it so that more energy has to be added in order to break the forces holding the ether molecules together as a solid comared to normal hydrocarbons. Alcohols, aldehydes, and ketones have higher melting points compared to ethers, for the same reason as described in the boiling points.
Since solubility is based on the similarities in intermolecular forces of the solute and the solvent, ethers have limited solubility in water. This is due to water having LDF, Dipole-Dipole, and Hydrogen Bonding intermolecular forces, while ethers have LDF, Dipole-Dipole, and Hydrogen Bonding (they can form hydrogen bonding IMFs with water but not themselves) intermolecular forces. These hydrogen bonding intermolecular forces that ethers form with water are not as strong as those in alcohols (that have hydroxyl groups instead of carbonyl groups, meaning they have hydrogens that can form hydrogen bonding IMFs with similar molecules) and ketones/aldehydes (as their oxygen to carbon double bond is more polar than the R-O-R bonds in ethers and can form slightly stronger hydrogen bonding IMFS with water). This means as the carbon chain increases on an ether the solubility will decrease more dramatically than with increasing the carbon chain on an alcohol. In terms of solubility with other ether molecules, they are soluble. This is due to ether molecules sharing the same intermolecular forces.
The density of ethers is consistent enough for them to be less dense than water, alcohols, and aldehydes/ketones (but much denser than most alkanes, alkenes, and alkynes), this is due to their intermolecular forces with each other, as they only have LDF and weak dipole-dipole intermolecular forces with each other, meaning they have a lower attraction to each other compared to water, alcohols, and aldehydes/ketones that have hydrogen bonding (stronger) intermolecular forces or also have dipole-dipole forces but are much stronger than ether's (ketones/aldehydes) meaning an increased attraction with each other. This attraction of ethers means they will be more compact (dense) than normal hydrocarbons but less compact (dense) than water, alcohols, and ketones/aldehydes in equal measurements/molar masses.
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