EasyChemistryHigh School (11–12)Organic Compounds with Functional Groups › AminesNumerical

Pentane (72 g/mol) boils at 36 °C. Butan-1-amine (73 g/mol) boils at 78 °C…

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Pentane ( $72\ \text{g/mol}$ ) boils at $36\ ^\circ\text{C}$ . Butan-1-amine ( $73\ \text{g/mol}$ ) boils at $78\ ^\circ\text{C}$ . Butan-1-ol ( $74\ \text{g/mol}$ ) boils at $118\ ^\circ\text{C}$ . 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

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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.

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