Skip to content
qorganica.es qorganica.comOrganic Chemistry made transparent Course map Español

SolutionsPhysical and Bond Properties

1. Which figure is correct?

Which of the two figures is the correct one?

First figure of the carbonyl group: carbon as a nucleophilic center, oxygen as an electrophilic center and a strong Lewis base, and α hydrogens with lower acidity than expected
Second figure of the carbonyl group: carbon as an electrophilic center, oxygen as a nucleophilic center and a weak Lewis base, and α hydrogens with higher acidity than expected
The first figure with its errors crossed out in red
The second figure, which is the correct one

The second one is correct. The carbonyl carbon (δ+) is an electrophilic center, sensitive to nucleophiles; the oxygen (δ−) is a nucleophilic center and a weak Lewis base, and the α hydrogens are more acidic than expected (pKa ≈ 19-20, much lower than that of an alkane).

2. Boiling points

Rank by increasing boiling point: butane, propanal, 1-propanol and acetone. Explain.

Butane (−0.5 °C) < propanal (48 °C) ≈ acetone (56 °C) < 1-propanol (97 °C). The four molecules have similar masses. Butane has only dispersion forces; propanal and acetone are polar (dipole-dipole interactions of the C=O) but cannot form hydrogen bonds between their molecules; 1-propanol can.

← Back to the exercises