Why is the boiling point of diethyl ether close to the boiling point of pentane?

The boiling point of diethyl ether (approximately 35 °C) is close to that of pentane (36.1 °C) because both molecules have similar molecular weights and rely on relatively weak intermolecular forces.

While diethyl ether is a polar molecule due to its oxygen atom, it lacks the ability to form intermolecular hydrogen bonds, which are responsible for the significantly higher boiling points seen in alcohols of comparable size. Consequently, the attractive forces between diethyl ether molecules are primarily limited to dipole-dipole interactions and London dispersion forces.1

Pentane, being a nonpolar alkane, is held together solely by weak London dispersion forces. Because the overall strength of these intermolecular attractions in diethyl ether is comparable to the cumulative London forces in pentane, the two compounds exhibit similar boiling points despite their differences in polarity.21