To arrange Diethyl ether, sec-Butyl alcohol, and pentane according to their expected boiling points, we need to consider the types of intermolecular forces present in each compound, as these forces largely determine boiling points.
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Pentane (C5H12): Pentane is an alkane and primarily exhibits London dispersion forces (induced dipole-induced dipole interactions). These forces are relatively weak compared to other types of intermolecular forces. Pentane has a boiling point of approximately 36 °C (97 °F).
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Diethyl ether (C4H10O): Diethyl ether is an organic compound that can engage in dipole-dipole interactions due to its ether functional group, as well as hydrogen bonding with water due to its oxygen atom. The boiling point of diethyl ether is about 34.6 °C (94.3 °F). Although it has some stronger dipole-dipole interactions compared to pentane, it is slightly lower in boiling point because ethers have a relatively small molecular weight and their weak hydrogen bonding does not significantly elevate the boiling point compared to alcohols.
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Sec-Butyl alcohol (C4H10O): Sec-butyl alcohol (or 2-butanol) has a hydroxyl (-OH) group that can form hydrogen bonds, which are significantly stronger than the dipole-dipole interactions in diethyl ether and the dispersion forces in pentane. As a result, sec-butyl alcohol has a higher boiling point, roughly around 99.5 °C (211 °F).
Based on this reasoning, the expected order of boiling points from lowest to highest is:
- Pentane (lowest boiling point)
- Diethyl ether
- Sec-butyl alcohol (highest boiling point)
This order reflects the increasing strength of intermolecular forces present in each compound, with hydrogen bonding in the alcohol resulting in the highest boiling point.
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