Pentane (72 g/mol) boils at 36 °C. Butan-1-amine (73 g/mol) boils at 78 °C…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Pentane () boils at . Butan-1-amine () boils at . Butan-1-ol () boils at . The three molar masses are almost the same. Find how many degrees the N-H hydrogen bonds lift the boiling point above pentane. Then find how many degrees the O-H hydrogen bonds lift it above the amine. Last, find the total rise from pentane to the alcohol.
Need a reminder? The key ideaShow
Primary and secondary amines make N-H hydrogen bonds between their molecules, so they boil above alkanes of similar molar mass. Alcohols boil higher still. Every amine can accept a hydrogen bond from water, so the smaller ones dissolve. The solubility of a solid or liquid in water is a mass in a fixed volume.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. Pentane to the amine. .
Step 2. Amine to the alcohol. .
Step 3. Total. , and agrees.
Answer: , and .
Check. The molar masses differ by 2 g/mol only, so almost all of the rise comes from hydrogen bonds.
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