Physical Properties of Alkenes
Alkenes contains a carbon-carbon double bond. This carbon-carbon double bond changes the physicals properties of alkenes. At room temperatue, alkenes exist in all three phases, solid, liquids, and gases. Melting and boiling points of alkenes are similar to that of alkanes, however, isomers of cis alkenes have lower melting points than that of trans isomers. Alkenes display a weak dipole-dipole interactions due to the electron-attracting sp2 carbon.
Ethene, Propene, and Butene exists as colorless gases. Members of the 5 or more carbons such as Pentene, Hexene, and Heptene are liquid, and members of the 15 carbons or more are solids.
Alkenes are lighter than water, therefore, are insoluble in water. Alkenes are only soluble in nonpolar solvent.
Boiling points of alkenes depends on more molecular mass (chain length). The more intermolecular mass is added, the higher the boiling point. Intermolecular forces of alkenes gets stronger with increase in the size of the molecules.
Melting points of alkenes depends on the packaging of the molecules. Alkenes have similar melting points to that of alkanes, however, in cis isomers molecules are package in a U-bending shape, therefore, will display a lower melting points to that of the trans isomers.
Chemical structure and fuctional groups can affect the polarity of alkenes compounds. The sp2 carbon is much more electron-withdrawing than the sp3 hybridize orbitals, therefore, creates a weak dipole along the substituent weak alkenly carbon bond. The two individual dipoles together form a net molecular dipole. In trans-subsituted alkenes, the dipole cancel each other out. In cis-subsituted alkenes there is a net dipole, therefore contributing to higher boiling in cis-isomers than trans-isomers.
1. Compound containing carbon-carbon double bonds are called:
2. Cis-alkenes exhibit a weak net dipole-dipole interactions:
3. Which has a lower melting poin
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