SolutionsPhysical and Bond Properties
1. Order by boiling point
Arrange in order of increasing boiling point: butanoic acid, ethyl acetate and pentane (masses 88, 88 and 72).
Pentane (36 °C) < ethyl acetate (77 °C) < butanoic acid (164 °C).
The ester is somewhat more polar than the alkane but cannot form hydrogen bonds between its molecules; the acid can.
2. Bond lengths
In methyl acetate the single C–O bond is 1.370 Å, shorter than in methanol (1.410 Å). What does this show?
That the lone pair of the alkoxy oxygen is partly delocalized towards the carbonyl (third resonance form), which gives the C–O bond a little double-bond character.