Understanding Boiling Point Trends
* Molecular Weight: Larger molecules generally have higher boiling points because they have more electrons and stronger London dispersion forces.
* Hydrogen Bonding: Alcohols can form strong hydrogen bonds, which significantly increase boiling points.
* Branching: Branching in a molecule decreases surface area, reducing London dispersion forces and lowering boiling points.
Let's Analyze
* Hexane (C6H14): A nonpolar alkane with a boiling point of 69°C.
* Alcohols: They have an -OH group, capable of hydrogen bonding.
Comparing Alcohols
* Methanol (CH3OH): Smallest alcohol, low boiling point.
* Ethanol (C2H5OH): Slightly larger, higher boiling point.
* Propanol (C3H7OH): Even larger, higher boiling point.
* Butanol (C4H9OH): Larger still, higher boiling point.
The Answer
The boiling points of alcohols increase as the carbon chain length increases. Since hexane is a relatively small molecule, we need to look for a small alcohol.
Ethanol (C2H5OH) has a boiling point of 78°C, which is closest to the boiling point of hexane (69°C).
Important Note: While ethanol is the closest, it's still important to remember that hydrogen bonding significantly increases the boiling points of alcohols compared to nonpolar alkanes like hexane.
