Is 2-propanol polar or nonpolar? – Polarity of 2-propanol

The question is –

Is 2-propanol polar or nonpolar?

Answer:

⇒ 2-propanol is polar.  

Explanation:

2- propanol or propan-2-ol (CH₃CH(OH)CH₃) is polar as it has a strongly polar hydroxyl (OH) functional group in it.

The unequal O-H, C-O, and C-H dipole moments do not get canceled equally in the overall molecular shape.  

2-propanol is a secondary alcohol. The hydroxyl (OH) functional group is present at carbon no. 2 i.e., the C-atom carrying two methyls (CH₃) groups, one on each side.

In this way, it comprises 1 O-H bond, 1 C-O bond, 2 C-C bonds, and 7 C-H bonds, respectively.

Each C-C bond is purely non-polar as it consists of two identical carbon atoms having zero or no electronegativity differences.

A C-H bond is weakly polar as it consists of an electronegativity difference of 0.35 units between the single covalently bonded carbon (E.N = 2.55) and hydrogen (E.N = 2.20) atoms.

In comparison, a C-O bond is moderately polar as the single-covalently bonded carbon and oxygen (E.N = 3.44) atoms have an electronegativity difference of 0.89 units, respectively.

However, an O-H bond is extremely polar as it possesses oxygen and a hydrogen atom containing an electronegativity difference of 1.24 units.

Oxygen being the most electronegative element in 2-propanol, strongly attracts the shared electron cloud from each C-H bond in addition to attracting the C-O and O-H bonded electrons.

Oppositely charged poles develop in the molecule as the O-atom gains a partial negative charge (δ^–) while each of the C and H-atoms gains partial positive charges (δ⁺ or δ⁺⁺) to denote an extreme electron deficiency.

The shape of the molecule w.r.t each C-atom is tetrahedral, identical to its ideal electron pair geometry.

Contrarily, the O-atom contains 2 lone pairs of electrons, which leads to strong lone pair-lone pair and lone pair-bond pair electronic repulsions. Hence, the shape of 2-propanol w.r.t this O-atom is bent, angular, or V-shaped.

Due to this bend in the molecular shape and geometry, the C-O and O-H dipole moments stay uncancelled along with the small dipole moment of each C-H bond.

The charged electron cloud stays non-uniformly distributed. That is why 2-propanol is overall polar (net µ = 1.66 Debye).

Also, check –

⇒ How to identify polar or nonpolar compounds?