Is Hexane (C6H14) polar or nonpolar? – Polarity of Hexane

Hexane or n-hexane is a straight-chain saturated hydrocarbon, represented by the chemical formula C₆H₁₄. Its molar mass is 86.18 g/mol. It exists as a highly flammable, colorless liquid with a gasoline-like odor.

n-hexane is mainly used as a laboratory solvent to extract oils from vegetable crops, also used as a cleaning agent in furniture, textiles, the printing industry., etc.

Let’s find out through this article whether hexane is a polar or a non-polar solvent.

Is Hexane polar or non-polar?

Hexane (C₆H₁₄) is non-polar.

C₆H₁₄ consists of 5 C-C single covalent bonds and 13 C-H bonds in an alicyclic or straight-chain arrangement.

Each C-C bond is purely non-polar as zero or no electronegativity difference exists between two identical carbon atoms.

Conversely, each C-H bond is very weakly polar, having a small electronegativity difference of 0.35 units between the bonded atoms.

However, it is due to the symmetrical tetrahedral shape of hexane w.r.t each C-atom that the small C-H dipole moments get canceled equally on each side of the molecule.

Thus, hexane (C₆H₁₄) is overall non-polar (net µ = 0).

Name of molecule	Hexane (C6H14)
Bond type	Non-polar covalent (C-C) Very weakly polar covalent (C-H)
Molecular geometry	Tetrahedral (w.r.t each C-atom)
Polar or non-polar?	Non-polar
Net dipole moment	Zero
Bond angles	109.5°

What makes a molecule polar or non-polar?

A molecule is polar if there is a non-uniform charge distribution present in it. If the charge distribution gets equally balanced in different parts, then that molecule is considered non-polar.

The following three factors mainly influence the polarity of a molecule:

• The electronegativity difference between two or more covalently bonded atoms
• Dipole moment
• Molecular geometry or shape

Now let us discuss the effect of the above three factors one by one to prove that hexane is overall non-polar.

Factors affecting the polarity of hexane

Electronegativity

It is defined as the ability of an elemental atom to attract a shared pair of electrons from a covalent chemical bond.

Electronegativity increases across a period in the Periodic Table while it decreases down the group.

Greater the electronegativity difference between bonded atoms in a molecule, the higher the bond polarity.

Carbon (C) belongs to Group IV A (or 14) of the Periodic Table. Its electronic configuration is 1s² 2s² 2p². It has a total of 4 valence electrons which means it is deficient in 4 more electrons in order to gain a stable octet electronic configuration.

Hydrogen (H) lies at the top of the Periodic Table in Group I A (or 1). Its electronic configuration is 1s¹, which implies it lacks 1 more electron to complete its duplet.

In C₆H₁₄, each C-atom is bonded to 2 other C-atoms and 2 H-atoms except the terminal C-atoms, which are bonded to 3 H-atoms each.

In this way, all the six carbon atoms attain a complete octet electronic configuration while the 14 H-atoms complete their duplets.

Conversely, as all 4 valence electrons of each C-atom get consumed in covalent bonding, thus, there is no lone pair of electrons on any of the C or H-atoms in the Lewis dot structure shown below.

Atom	Electronic configuration	Valence electrons
Hydrogen (1H)	1s1	1
Carbon (6C)	1s2 2s2 2p2	4

Zero or no electronegativity difference exists between two identical carbon atoms in each C-C bond. Thus all C-C bonds are purely non-polar as the shared electron cloud stays uniformly distributed.

In contrast, an electronegativity difference of 0.35 units exists between a carbon (E.N = 2.55) and a hydrogen (E.N = 2.20) atom in each C-H bond.

It is less than that required for a covalent chemical bond to be polar as per Pauling’s electronegativity scale i.e., 0.4 units.

Still, each C-H bonded C-atom gains a partial negative (δ^–) charge while the corresponding H-atom obtains a partial positive (δ⁺) charge, considering the fact that it is formed between two dissimilar atoms, which may lead to a slight distortion in electron cloud distribution.

As a result, each C-H bond of hexane is considered very weakly polar, individually.

Dipole moment

Dipole moment (μ) is a vector quantity that points from the positive pole to the negative pole of a bond or a molecule.

It is mathematically calculated as a product of the magnitude of charge (Q) and charges separation (r). The dipole moment is expressed in a unit called Debye (D).

The dipole moment of a polar covalent bond conventionally points from the positive center to the center of the negative charge.

So, in hexane, the C-C bonds have no dipole moments, while the small dipole moment of each C-H bond points from H^δ+ to C^δ-, as shown below.

Molecular geometry

According to the valence shell electron pair repulsion (VSEPR) theory of chemical bonding, hexane (C₆H₁₄) is an AX₄-type molecule w.r.t each C-atom.

To one carbon atom at the center (A), four bond pairs (X) are attached i.e., 2 C-atoms and 2 H-atoms or 1 C-atom and 3 H-atoms (at the terminals), and there is no lone pair of electrons (E). Thus, the shape of the molecule w.r.t each C-atom is tetrahedral.

The absence of any lone pairs of electrons on any one C-atom in C₆H₁₄ ensures there are no lone pair-lone pair or lone pair-bond pair electronic repulsions to distort the shape and geometry of the molecule.

It is due to this symmetrical tetrahedral shape of C₆H₁₄ w.r.t each C-atom that the small C-H dipole moments get canceled equally in opposite directions to yield an overall non-polar molecule (net µ= 0).

FAQ

Is hexane (C6H14) polar or not?

Hexane (C6H14) is non-polar. It consists of 5 C-C single covalent bonds and 14 C-H bonds. All the C-C single bonds are purely non-polar, as zero or no electronegativity difference exists between identical carbon atoms. A very small (0.35 units) electronegativity difference is present between a C and an H-atom, so a C-H bond is very weakly polar. The small C-H dipole moments get canceled equally in opposite directions in the tetrahedral shape of the molecule w.r.t each C-atom; thus, hexane (C6H14) is overall non-polar (net µ = 0).

Which is more polar: pentane, hexane, heptane, or octane?

All the above molecules are non-polar saturated hydrocarbons (net µ =0). Pentane (C5H12), hexane (C6H14), heptane (C7H16), and octane (C8H18) consist of only two types of bonds i.e., C-C and C-H. No electronegativity difference is present between identical carbon atoms. However, a very small electronegativity difference is present between a carbon and a hydrogen atom. The charged electron cloud stays uniformly distributed due to the tetrahedral shape of each molecule w.r.t each C-atom, resulting in an overall non-polar molecule.

Why doesn’t NaCl dissolve in non-polar solvents such as hexane (C6H14)?

NaCl is a polar ionic compound. Like dissolves like so non-polar solvents such as hexane (C6H14) cannot solubilize polar NaCl as no forces of attraction exist between the two.

Which is polar between the two: hexane or dichloromethane?

Hexane (C6H14) is non-polar, while dichloromethane (CH2Cl2) is polar. A molecule’s polarity depends upon the electronegativity difference between the bonded atoms and the shape of the molecule. The shape of both C6H14 and CH2Cl2 w.r.t the central C-atom is tetrahedral. C6H14 is composed of atoms having very small to no electronegativity differences. CH2Cl2 consists of two highly electronegative Cl-atoms. A relatively higher electronegativity difference of 0.61 units exists between a carbon and a chlorine atom. The C-Cl dipole moments do not get canceled with the small C-H dipole moments to yield an overall polar CH2Cl2 molecule (net µ > 0).

Is cyclohexane (C6H12) more polar than n-hexane (C6H14)?

No. Both cyclohexane and n-hexane are non-polar molecules. Both consist of the same type of atoms i.e., C-C and C-H covalently bonded together with very little electronegativity differences. The small C-H dipole moments get canceled in the tetrahedral shapes of C6H14 w.r.t each C-atom and of hexagonally arranged C6H12 w.r.t each C-atom, respectively.

Are hexane and water-miscible with each other?

No. Like dissolves like. As water (H2O) is a polar solvent while hexane (C6H14) is non-polar, so hexane and water are immiscible. Two separate layers are formed when you shake hexane with water, as the long hydrocarbon chain (C6H14) cannot develop hydrogen bonding or any other force of attraction with polar H2O molecules.

Is there a formal charge present on hexane?

Formal charge on an atom = [ valence electrons – non-bonding electrons- ½ (bonding electrons)] For each C-atom   Valence electrons = 4 Bonding electrons = 8 Non-bonding electrons = 0 ∴ Formal charge on each C-atom = 4 – 0 – 8/2 = 4 – 0 – 4 = 4 – 4 = 0 For each H-atom Valence electrons = 1 Bonding electrons = 2 Non-bonding electrons = 0 ∴ Formal charge on each H-atom = 1 – 0 – 2/2 = 1 – 0 – 1 = 1 – 1 = 0 Zero formal charges are present on all the C and H-atoms in the C6H14 molecule. Thus, there is no or zero overall formal charges on hexane.

Summary

• Hexane (C₆H₁₄) is a saturated hydrocarbon containing all C-C single covalent bonds and C-H bonds.
• Each C-C bond is non-polar as zero or no electronegativity difference is present between two identical carbon atoms.
• A C-H bond is weakly polar (almost non-polar as per Pauling’s electronegativity scale) as an electronegativity difference of only 0.35 units is present between a carbon and a hydrogen atom.
• The small C-H dipole moments get canceled equally due to the symmetrical tetrahedral shape of n-hexane w.r.t each C-atom. Hence, hexane (C₆H₁₄) is overall non-polar (net µ = 0).

References

•  ‘’Hexane.’’ S.R. Clough. Encyclopedia of Toxicology, Third Edition. Elsevier (2014). Retrieved from https://www.sciencedirect.com/science/article/pii/B9780123864543003973