CHEM 281 Chapter Notes - Chapter 3: London Dispersion Force, Tennis Ball, Boiling Point
30 Aug 2018
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Chapter 3 notes part 10: an introduction to organic compounds. The greater the area of contact, the stronger the london dispersion forces and the greater the amount of energy needed to overcome them. If you look at the boiling points of the alkanes listed in table 3. 1, you see that they increase as their molecular weight increases, because each additional methylene (ch2) group increases the area of contact between the molecules. The four smallest alkanes have boiling points below room temperature, so they exist as gases at room temperature. Branching lowers a compound"s boiling point by reducing the area of contact. Thus, if two alkanes have the same molecular weight, the more highly branched one will have a lower boiling point. The boiling points of a series of ethers, alkyl halides, alcohols, or amines also increase with increasing molecular weight because of the increase in the london dispersion forces.
