SolutionsPhysical and Bond Properties
1. Boiling point
Acetyl chloride (mass 78.5) boils at 51 °C and acetic acid (mass 60) at 118 °C. Explain.
The acid chloride has no hydrogens able to form hydrogen bonds; the acid forms dimers. So the halide, though heavier, boils much lower, in the range of an alkane of similar mass.
2. Resonance
The C–Cl bond of acetyl chloride (1.743 Å) is almost the same as in chloromethane (1.741 Å). What does this say about the third resonance form?
That its contribution is minimal: chlorine hardly shares its lone pair with the carbonyl, because its 3p orbitals overlap poorly with the carbon 2p orbital.