The key difference between naphthalene and p-dichlorobenzene is that naphthalene has two ring structures fused with each other, whereas p-dichlorobenzene has a single ring structure with chlorine substituents.
Naphthalene and p-dichlorobenzene are organic compounds we can categorize as aromatic compounds because these compounds have ring structures with alternating double bonds inside the ring.
CONTENTS
1. Overview and Key Difference
2. What is Naphthalene
3. What is p-Dichlorobenzene
4. Side by Side Comparison – Naphthalene vs p-Dichlorobenzene in Tabular Form
5. Summary
What is Naphthalene?
Naphthalene is an organic compound having the chemical formula C10H8. We can identify this compound as the simplest polycyclic aromatic hydrocarbon compound. This substance occurs as a white crystalline solid that has a characteristic odour similar to coal tar, even at very low concentrations. When considering the structure of naphthalene, it has fused pair of benzene rings.
Figure 01: Chemical Structure of Naphthalene
We can observe a naphthalene molecule as a fusion of a pair of benzene rings. This leads to the classification of this compound as a benzenoid polycyclic aromatic hydrocarbon or PAH. There are eight carbon atoms that are not shared between the two ring structures. Each of these eight carbon atoms contains one hydrogen atom per carbon atom. In the nomenclature of this naphthalene molecule, the eight carbon atoms are numbered from 1 to 8 in a sequence around the perimeter of the molecule. This numbering starts with the carbon atom that is adjacent to a shared one. Generally, the shared carbon atoms are numbered as 4a and 8a.
Naphthalene molecule has a planar structure. However, unlike in the benzene ring, the C-C bonds in this molecule have different lengths. We can find this difference through X-ray diffraction, and it is consistent with the valence bond model in naphthalene.
Naphthalene substance is useful as a precursor to other chemical compounds, for the production of phthalic anhydride, many azo dyes, insecticides and other useful agrochemicals.
What is p-Dichlorobenzene?
P-dichlorobenzene is an organic compound having the chemical formula C6H4Cl2. The chemical name of this compound is 1.4-dichlorobenzene because two chlorine atoms are attached to the benzene ring at positions 1 and 4. It mainly occurs as a colourless solid substance with a mothball-like strong odour.
If we look at the chemical structure of p-dichlorobenzene, it contains a benzene ring consisting of two chlorine atoms that have replaced the hydrogen atoms on opposing sites of the ring. This structure is named a “para” structure; hence the compound is known as “p-dichlorobenzene”.
This substance is useful as a disinfectant, pesticide, and deodorant. This material can be used to replace naphthalene in the production of mothballs because naphthalene has greater flammability. Also, p-dichlorobenzene is important as a precursor for the production of the chemical and thermal resistant polymer material, poly(p-phenylene sulfide).
We can produce this substance through the chlorination of a benzene ring using ferric chloride as the catalyst for the reaction. There can be an impurity made through this process, which is the 1,2-dichlorobenzene isomer. Therefore, we need to purify the resulting product mixture using a fractional crystallization process.
What is the Difference Between Naphthalene and p-Dichlorobenzene?
Naphthalene and p-dichlorobenzene are aromatic organic compounds. The key difference between naphthalene and p-dichlorobenzene is that naphthalene has two ring structures fused with each other, whereas p-dichlorobenzene has a single ring structure with chlorine substituents. Moreover, another difference between naphthalene and p-dichlorobenzene is that the naphthalene is derived from coal tar while the p-dichlorobenzene is derived from the chlorination of benzene ring using ferric chloride as the catalyst for the reaction.
The below infographic lists the differences between naphthalene and p-dichlorobenzene in tabular form for side by side comparison.
Summary – Naphthalene vs p-Dichlorobenzene
Naphthalene and p-dichlorobenzene are aromatic organic compounds. The key difference between naphthalene and p-dichlorobenzene is that naphthalene has two ring structures fused with each other, whereas p-dichlorobenzene has a single ring structure with chlorine substituents.
Reference:
1. “Naphthalene.” Wikipedia, Wikimedia Foundation, 10 Mar. 2021, Available here.
Image Courtesy:
1. “Naphthalene numbering” By Ed – Own work (Public Domain) via Commons Wikimedia