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Naphthalene

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What is Naphthalene?

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Before starting with the naphthalene, first you need to understand what is an aromatic compound. Aromatic compounds are the ring compound that contains a double and single bond in an alternate manner, and follows the huckel rule. Let’s come to our main question, what is a naphthalene? Naphthalene is an aromatic hydrocarbon, consisting of two or more fused aromatic benzene rings. These are polynuclear aromatic hydrocarbons. In short, naphthalene is fused with hydrocarbon. In this article we have covered the all important points about the naphthalene like use of naphthalene, structure of naphthalene, and resonance in naphthalene.


Structure of Naphthalene

Naphthalene is a member of a polynuclear aromatic hydrocarbon where two aromatic benzene rings are fused together at the ortho position.


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The bond length at double bond position is around 1.36 angstrom, and the bond length at single bond position is around 1.40 angstrom. Naphthalene molecule shows the resonance in its structure. It forms a resonance hybrid. Naphthalene molecules show three resonance structures. These structures are known as canonical structures. Naphthalene forms three resonating structures. These structures are shown below for better understanding.


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In these structures the pi electrons are delocalised from one position to another. This delocalisation phenomena leads to the lowering of electronic energy of the system. In the naphthalene molecule the carbon 1 - carbon 2 bond length is shorter than the carbon 2-carbon 3 bond length. All carbons are sp2 hybridised and have unused p-orbitals with one electron. In naphthalene sigma bond count is eleven.


Properties of Naphthalene:

The physical properties and chemical properties of naphthalene are discussed below:

  1. Naphthalene exists in crystalline form.

  2. Naphthalene is generally white in colour. It is also found in transparent to brownish colour.

  3. The molecular weight of naphthalene is 128.18 g/mol.

  4. Naphthalene is insoluble in water at a normal room temperature.

  5. Naphthalene has an aromatic odour.

  6. The vapour pressure of naphthalene is 0.087 mmHg.

Synthesis of Naphthalene

  1. From Coal Tar- Naphthalene can be obtained from the coaltar, by making naphthalene crystals. These crystals can be formed by the middle oil fraction. The crystals produced in this process are subjected to the sulphuric acid for the purification process. At the end the pure naphthalene crystals are formed.

  2. Haworth Synthesis- In this process, benzene to naphthalene is produced. The benzene ring is first subjected to the acylation process. This reaction starts with the friedel craft acylation of benzene ring with the succinic anhydride, then a series of reduction reactions undergoes. Finally, a naphthalene molecule is produced by dehydrogenation.

Naphthalene in Water

The solubility of naphthalene in water can be determined by its structure. The naphthalene is a polyatomic hydrocarbon. The large number of carbon atoms makes it a hydrophobic molecule. Due to this hydrophobic structure, the naphthalene in water is insoluble. In this article naphthalene liquid structure is not discussed in detail.


Different Forms of Naphthalene

1. Refined naphthalene

2. Alkyl naphthalene

3. Naphthalene solid

Refined Naphthalene- Refined naphthalene powder is raw material, used for the production of various organic compounds. It is used in agriculture and the fabric industry.

Alkyl Naphthalene- Alkyl naphthalene generally exists in a form of salt. The most common and widely used alkyl naphthalene is alkyl naphthalene sulfonate sodium salt. It occurs in powder form. PH of this compound is generally more than 7 (slightly basic in nature). It acts as a surfactant. 

Naphthalene Solid- Naphthalene solid is a very common form of naphthalene. It occurs white in colour. It is a crystalline volatile solid. It has odour like coal tar.


Use of Naphthalene

The main use of naphthalene are discussed below:

  • Naphthalene is used in making carbaryl drugs. These drugs are used in making insecticides.

  • Naphthalene is used in making nadoxolol drug for beta blocking.

  • The Sulphonated form of naphthalene used as surfactants.

  • Naphthalene is used in making synthetic dyes.

  • amino naphthalene sulfonic acid is used in making different types of dyes.

  • Molten naphthalene is used for making solvents for an aromatic compound.

Did You Know?

  • You may be shocked to hear that naphthalene can be present in cigarette smoke, vehicle exhaust, and forest fire smoke.

  • In the United States, naphthalene was first licenced as a pesticide in 1948.

  • Insecticides include naphthalene.

  • Naphthalene is a highly flammable material.

FAQ (Frequently Asked Questions)

1. What are the Different Uses of Naphthalene?

Answer: The different use of naphthalene is discussed below:

  • Carbaryl medicines are made from naphthalene. Insecticides are made with these medications.

  • The chemical naphthalene is used to make the beta-blocking drug nadoxolol.

  • Surfactants made from the sulphonated form of naphthalene.

  • Synthetic dyes are made from naphthalene.

  • Different forms of dyes include amino naphthalene sulfonic acid.

  • The solvents for an aromat are made from molten naphthalene.

2. Explain the Properties of Naphthalene.

Answer: The various properties of naphthalene are discussed below:

  • Naphthalene is a crystalline substance.

  • The colour of naphthalene is usually white. It also comes in a range of colours from clear to brownish.

  • Naphthalene has a molecular weight of 128.18 g/mol.

  • At room temperature, naphthalene is insoluble in water.

  • The odour of naphthalene is aromatic.

  • Naphthalene has a vapour pressure of 0.087 mmHg.