Is Vinegar (CH3COOH) polar or nonpolar? - Polarity of Vinegar

Vinegar, a famous ingredient of salad dressings and sauces such as ketchup and mayonnaise, is an aqueous solution of acetic acid (CH₃COOH). In addition to acetic acid and water, some food flavorings and/or preservatives may also be used in the commercial preparation of vinegar.

Do you know whether it is polar or non-polar?

Let’s find out the answer to the above question through this article.

Is vinegar polar or non-polar?

Vinegar is polar.

Acetic acid (CH₃COOH) is the main component of vinegar. A CH₃COOH molecule is composed of two C-atoms, two O-atoms and four H-atoms.

The C-C bond present in CH₃COOH is purely non-polar, the C-H bonds are very weakly polar owing to an electronegativity difference of 0.35 units between the bonded atoms.

Contrarily, the C=O and O-H bonds are strongly polar due to an electronegativity difference of 0.89 units and 1.24 units, respectively, between the concerning atoms.

 It is due to the asymmetric bent shape of the acetic acid molecule w.r.t the O-H bonded O-atom that the C=O and O-H dipole moments do not get canceled. Consequently, CH₃COOH is a polar molecule overall (net µ > 0).

The solution of polar CH₃COOH in polar H₂O molecules results in an overall polar chemical solution i.e., vinegar.

Name of the substance	Vinegar
Chemical composition	A dilute solution of acetic acid (CH3COOH) in water
Name of the molecule	Acetic acid (CH3COOH)
Bond type	Polar covalent
Molecular geometry	Trigonal planar (w.r.t central C-atom), angular or V-shaped (w.r.t O-atom)
Polar or non-polar?	Polar
Net dipole moment	1.7 Debye
Bond angles	∠ C-O-H = 107°, ∠ H-C-H= 108.1° , ∠ C-C-O = 110°,  ∠ C-C=O = 126.6°

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 or molecular ion 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 how the above three factors make acetic acid (CH₃COOH) a polar molecule and, consequently, vinegar a polar chemical solution.  

Factors affecting the polarity of Vinegar (CH₃COOH)

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.

Three different elemental atoms are present in a CH₃COOH molecule. The carbon (C) atom belongs to Group IV A (or 14) of the Periodic Table. Its electronic configuration is 1s² 2s² 2p², which shows it has a total of 4 valence electrons. Each C-atom is thus deficient in 4 more valence electrons in order to achieve a complete octet electronic configuration.

The electronic configuration of an oxygen (O) atom is 1s² 2s² 2p⁴. It lies in Group VI A (or 16) of the Periodic Table and thus possesses 6 valence electrons. This implies that each O-atom needs 2 more valence electrons to complete its octet.

Hydrogen (H) lies at the top of the Periodic Table, containing a single valence electron only. It needs 1 more electron to achieve a complete duplet.

The Lewis dot structure of CH₃COOH displays a C-C bond at the center. The central C-atom is bonded to a methyl (CH₃) functional group on one side, a =O atom, and a hydroxyl (-OH) functional group.

In the above structure, all the C and O-atoms have a complete octet, while all the H-atoms possess a complete duplet electronic configuration.

There is no lone pair of electrons on either of the two C-atoms. In contrast, the terminal O-atoms carry 2 lone pairs of electrons each.

Atom	Electronic configuration	Valence electrons
Hydrogen (1H)	1s1	1
Carbon (6C)	1s2 2s2 2p2	4
Oxygen (8O)	1s2 2s2 2p4	6

A C-C single covalent bond is purely non-polar as it is formed between two identical carbon atoms with a zero electronegativity difference.

The C-H bonds are very weakly polar, having an electronegativity difference of 0.35 units between the bonded atoms.

The C=O bond is strongly polar due to an electronegativity difference of 0.89 units between the bonded carbon (E.N = 2.55) and oxygen (E.N = 3.44) atoms.

The O-H bond is extremely polar as per an electronegativity difference of 1.24 units between the bonded oxygen and hydrogen (E.N = 2.20) atoms.

Both oxygens in the carboxyl (COOH) functional group thus gain partial negative (δ^–) charges while the corresponding carbon and hydrogen atoms gain partial positive charges (δ⁺).

Two strongly electronegative O-atoms not only attract the C=O and O-H bonded electrons but also attract the shared electron cloud from each C-H bond as well. As a result, strong partial positive charges appear on the atoms present in the methyl (CH₃) functional group.

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.

In the CH₃COOH molecule, the C-H dipole moments point from H^δ+++ to C^δ++, the C=O dipole moment points from C^δ+ to O^δ– while the O-H dipole moment is directed from H^δ+ to O^δ– as shown below.

Molecular geometry

According to the valence shell electron pair repulsion (VSEPR) theory of chemical bonding, acetic acid is an AX₃ type molecule as per the central C-atom. To one C-atom at the center (A), three bond pairs (X) are directly attached i.e., a C-atom, an O-atom, and an O-H group, while it has no lone pair of electrons (E).

The molecule thus possesses a trigonal planar shape w.r.t the central C-atom. However, the acetic acid molecules of vinegar possess a tetrahedral shape w.r.t the other C-atom and a bent shape w.r.t O-H bonded O-atom.

2 lone pair of electrons present on the O-H bonded oxygen atom leads to strong lone pair-lone pair and lone pair-bond pair electronic repulsions. This results in an asymmetric bent shape.

The C-H, C=O and O-H dipole moments dot net get cancelled, and the charged electron cloud stays non-uniformly spread over the molecule. Each CH₃COOH molecule is thus strongly polar (net µ = 1.7 D).

Like dissolves like. Polar CH₃COOH molecules easily solubilize in polar H₂O molecules (net µ = 1.84 D) by developing strong intermolecular forces of attraction, such as hydrogen bonding (refer to the figure drawn below).

A dilute aqueous solution of acetic acid implies that in vinegar small number of CH₃COOH molecules are dissolved in a comparatively large amount of water.

The overall polarity effect is enhanced. In short, vinegar is extremely polar in nature.

Also, check

• Acetic acid (CH₃COOH) lewis structure, molecular geometry, bond angle, hybridization
• Is Soap an acid or base?
• How to identify polar and nonpolar molecules?
• Is Water (H₂O) polar or nonpolar?

FAQ

Is vinegar polar or non-polar?

Vinegar is polar in nature. It is chemically composed of a dilute aqueous solution of acetic acid (CH3COOH). CH3COOH is a polar molecule. The C=O, C-O, and O-H bonds present in an acetic acid molecule are highly polar, owing to an electronegativity difference of 0.89 units and 1.24 units between the bonded atoms, respectively. The C=O and O-H dipole moments do not get canceled in the asymmetric bent shape of the molecule w.r.t O-atom present in the hydroxyl group. Thus, CH3COOH is overall polar (net µ > 0). The dissolution of polar CH3COOH molecules in polar H2O molecules yields a homogenous, viscous liquid i.e., polar vinegar.

Vinegar dissolves in water. State, whether this statement is: A,) true or B) false.

Answer:  A) true. Explanation: Vinegar is prepared by dissolving acetic acid (CH3COOH) in water. CH3COOH is a polar molecule that gets dissolved in water via hydrogen bonding. The Oδ- end of each CH3COOH molecule develops a strong force of attraction with Hδ+ of H2O and vice versa.

Is vinegar acidic, base, or neutral?

Vinegar is acidic in nature. The dissolution of acetic acid in water yields an overall acidic solution. CH3COOH is a weak acid that partially ionizes in water to release H+ ions. The concentration of H+ or H3O+ ions present in the solution is measured as pH, where pH = -log10 [H+]. The pH of the weakly acidic vinegar lies between 2-3.

How is vinegar prepared from acetic acid at an industrial scale?  Does soap dissolve in water?

Vinegar is prepared by the fermentation of ethanol (CH3CH2OH) into acetic acid, aka ethanoic acid (CH3COOH). Trace amounts of other chemicals, such as food flavorings and preservatives, are also added. Vinegar is usually a dilute solution of acetic acid in water. However, the concentration of acetic acid differs for different types of vinegar prepared. Distilled vinegar is 5-8% concentrated, Spirit of vinegar is 5-20% concentrated, while apple cider vinegar has about 5-6 % acetic acid present in it.

Which out of the two is more polar? CH3COOH or CH3CH2OH

Both ethanoic acid (CH3COOH) and ethanol (CH3CH2OH) are polar molecules owing to a specific electronegativity difference between the bonded atoms (especially in the hydroxyl O-H functional group) and an asymmetric bent shape w.r.t terminal O-atom. However, CH3CH2OH is more polar than CH3COOH. This is because, in CH3COOH, the carbon carrying the O-H bond is also double-covalently bonded to another O atom. The O-H shared electron cloud also gets involved in the resonance present in the molecule; the charged electron cloud gets comparatively uniformly dispersed over the molecule, thus reducing the overall molecular polarity. Contrarily, CH3CH2OH is not resonance stabilized, so it is comparatively more polar.

Summary

• Vinegar is polar in nature.
• Vinegar is chemically composed of a dilute aqueous solution of acetic acid (CH₃COOH).
• CH₃COOH is a polar molecule. It consists of weakly polar C-H bonds, a polar C=O bond, and a strongly polar O-H bond.
• The high electronegativity difference between bonded atoms in the C=O and O-H bonds results in specific dipole moment values.
• The C=O and O-H dipole moments do not get canceled in the asymmetric bent shape of the acetic acid molecule w.r.t O-atom.
• The charged electron cloud stays non-uniformly distributed; thus, CH₃COOH is overall polar (net µ = 1.7 D).
• Polar CH₃COOH molecules get dissolved in polar H₂O via H-bonding, yielding a homogenous solution (vinegar) that is unquestionably polar in nature.