Polarity Comparison: Diethyl Ether vs. Hexane
Diethyl ether is more polar than hexane. This difference arises mainly from the presence of oxygen atoms bonded to carbon in diethyl ether, which creates bonds with significant dipole moments. Hexane, composed solely of carbon and hydrogen atoms bonded together, has very low polarity.
Electronegativity and Dipole Moments
Polarity in molecules depends on the difference in electronegativity between bonded atoms. Oxygen is more electronegative than carbon and hydrogen, while carbon and hydrogen have more similar electronegativities. For example:
- The C–O bond in diethyl ether has a larger electronegativity difference than the C–H bond in hexane.
- This difference creates notable dipole moments in the C–O bonds of diethyl ether.
Dipole moments are vectors, so their spatial arrangement matters. In diethyl ether, these vectors partially cancel but do not eliminate the overall molecular dipole moment. This makes diethyl ether polar, whereas hexane’s C–H bonds have weak dipoles that mostly cancel out, resulting in a nonpolar molecule.
Dielectric Constant as a Polarity Indicator
Dielectric constant (relative permittivity) measures a substance’s ability to reduce the electric field within it, reflecting polarity. Diethyl ether has a dielectric constant around 4.3, significantly higher than hexane’s value near 1.9. This difference confirms that diethyl ether is more polar.
Summary Table: Polarity Factors
| Property | Diethyl Ether | Hexane |
|---|---|---|
| Main Bonds | C-O and C-H | C-H only |
| Electronegativity Difference | High (C–O) | Low (C–H) |
| Dipole Moment | Moderate (partial vector cancellation) | Very low (vectors nearly cancel) |
| Dielectric Constant | ~4.3 | ~1.9 |
| Overall Polarity | Polar | Nonpolar |
Key Points
- Diethyl ether’s C–O bonds create stronger dipoles than hexane’s C–H bonds.
- Though dipole vectors partly cancel in diethyl ether, molecular polarity remains.
- Hexane’s bonds are nearly nonpolar, making it overall nonpolar.
- Dielectric constants support diethyl ether’s greater polarity.
Is diethyl ether more polar than hexane?
Yes, diethyl ether is more polar than hexane. This is because diethyl ether contains carbon-oxygen bonds with larger dipole moments, unlike hexane, which only has carbon-hydrogen bonds.
Why do carbon-oxygen bonds in diethyl ether affect polarity more than carbon-hydrogen bonds in hexane?
The carbon-oxygen bond has a greater electronegativity difference than the carbon-hydrogen bond. The difference causes stronger dipole moments in diethyl ether, increasing its polarity compared to hexane.
Does diethyl ether’s polarity make it a strongly polar molecule overall?
Not exactly. Although the C-O bonds have large dipole moments, their vectors partially cancel out. This means diethyl ether isn’t highly polar overall but still more polar than hexane.
How can dielectric constant relate to polarity in these solvents?
A higher dielectric constant usually indicates greater polarity. Diethyl ether has a higher dielectric constant than hexane, supporting that it’s more polar.
Are ethers always more polar than alkanes?
Yes, ethers, like diethyl ether, generally have higher polarity than alkanes such as hexane because of their oxygen atoms and the resulting dipole moments.
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