P roperties
Chemical/Physical Properties
The boiling points for alkynes and alkenes is extremely similar to alkanes. They have relatively low boiling points for the same reasons as alkanes. This is due to weak intermolecular forces (LDF) present in alkenes/alkynes. These forces make it require less energy to break their attraction to one another, making them have a lower boiling point. Along with this, as you add carbons to an alkene/alkyne, the boiling point increases due to the increased amount of electrons. This makes the LDF intermolecular force stronger as there is a higher chance for temporary dipoles.
The melting point for alkynes/alkenes flucutates (but always increases and is generally low) as you add carbons to it. This is due to the crystal latice structure of hydrocarbons favoring symmetrical molecules when it comes to the melting point, and if you have an even number of carbons atoms the molecule will be symmetrical. (Same as alkanes)
Since solubility is based on the similarities in intermolecular forces of the solute and the solvent, alkenes/alkynes are gerneally insoluble in water. This is due to water having LDF, Dipole-Dipole, and Hydrogen Bonding intermolecular forces, while alkenes/alkynes only have LDF intermolecular forces. In terms of solubility with other alkenes/alkynes, they are soluble. This is due to alkenes/alkynes sharing the same intermolecular forces of LDF (only). (Same as alkanes)
The density of alkenes/alkynes is consistent enough for them to be less dense than water, this is due to their weak intermolecular forces which make them less compact (less dense).
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