Question

Bond angles and intermolecular forces present?

Answer 1

Here's what I got.

Explanation:

You can give the approximate value of those angles by looking at the hybridization of the two adjacent carbon atoms.

For angle `alpha`, the carbon atom, which belongs to a carboxyl group, `-"C"("O")"OH"`, is surrounded by three regions of electron density

• a single bond to the oxygen atom that belongs to the hydroxyl group, `-"OH"`
• a double bond to the other oxygen atom
• a single bond to another carbon atom

This means that the carbon atom has a steric number equal to `3`, and thus uses `3` hybrid orbitals to form the aforementioned bonds.

As a result, this carbon atom will be `"sp"^2` hybridized, which implies that the `alpha` angle is approximately `120^@`.

For angle `beta`, the carbon atom, which belongs to a methyl group, `-"CH"_3`, is surrounded by four regions of electron density

• a single bond to another carbon atom
• three single bonds to hydrogen atoms

This carbon has a steric number equal to `4`, and thus uses `5` hybrid orbitals to form the aforementioned bonds.

As a result, this carbon atom will be `"sp"^3` hybridized, which implies that the `beta` angle is approximately `109.5^@`.

This can be seen by looking at a molecule of pyruvic acid

Now, a pyruvic acid molecule is polar because of the presence of the carboxyl group and of the carbonyl group, `-"C=O"`.

This means that it exhibits dipole - dipole interactions due to the existence of permanent dipoles.

Moreover, because pyruvic acid has a hydrogen atom directly bonded to an oxygen atom in the hydroxyl group, it can act as a hydrogen bond donor.

The molecule can also act as a hydrogen bond acceptor due to the presence of the carbonyl group, which means that pyruvic acid can form hydrogen bonds.

Finally, all molecules, regardless if they are polar or non-polar, exhibit London dispersion forces due to random variations in the distribution of their electron clouds.