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What's the Difference Between Aliphatic and Aromatic Hydrocarbons?

Published November 21, 2021

There are many different types of hydrocarbons, but what is the difference between aliphatic and aromatic hydrocarbons? In this blog post, we will explore what makes these two types of hydrocarbons different from one another!

Aliphatic hydrocarbons are organic compounds that mainly consist of carbon and hydrogen atoms. They can be straight-chained or branched, but they do not have any rings of alternating single and double bonds. Aliphatic hydrocarbons may be saturated (joined mainly by single bonds) or unsaturated (joined by double bonds or triple bonds). Aromatic hydrocarbons are also organic compounds containing only carbon and hydrogen atoms, but they contain at least one benzene ring with alternating single and double bonds.

What are Aliphatic hydrocarbons?

A Molecule of Methane, an Aliphatic Compound

As one can understand, this type of hydrocarbon is the most common and rarely has branches in its carbon chain. These types of molecules are further broken down into saturated and unsaturated. In general, these have a lower boiling point than their branched counterparts due to stronger intermolecular forces between each molecule which results from weaker van der Waals bonds formed because there aren't any branching that could lead to an increase or decrease in size or shape of the compound itself.

What are Aromatic hydrocarbons?

A Molecule of Benzene, the least complex Aromatic Hydrocarbon

Aromatics usually contain multiple double bonds and a series of atoms that form a ring. The double bond in the hydrocarbon is formed by hydrogen which makes it more reactive than its counterpart aliphatic compounds due to its higher electron density because of delocalization around the aromatic system. As far as boiling points go, this group contains both varying boiling point examples such as benzene (80C) whereas hexane has one at 69 C. This boils down to how much surface area they have since when there are branching groups on each molecule it can potentially increase or decrease depending on if there are branches coming off the main carbon chain itself leading to an overall change in size/shape.

Key Differences Between The Two

Chain structure

Aromatics have a benzene ring structure while aliphatics do not contain any cyclic structures in their compound formula. The difference between aromatic and aliphatic hydrocarbon lies in how they are classified: aliphatic has an open-chain & closed-chain molecular structure, whereas aromatic only have a closed chain structure. This means that aromatics consist of compounds with closed carbon chains (cyclic), hence having different chemical properties than those without such rings. In addition to this, there must be at least two or more double or triple covalent bonds within each molecule for it to be considered as an aromatic hydrocarbon rather than an alkane.

The difference in chain structure is one of the key differences between aliphatic and aromatic hydrocarbons. Aliphatic compounds are composed of carbon chains that may be straight or branched. While aromatic ones always have a planar structure that is circular in shape with single ring structures bonded to each other along their lengths.

The main difference between aliphatic and aromatic hydrocarbons is that they contain different functional groups. Aliphatics do not have a benzene ring, while aromatics do. Instead of the two carbon-carbon double bonds found in aliphatic, or one single bond and one triple bond as with an alkene, aromatics feature alternating double and single bonds between their six atoms which makes them more stable than aliphatics because there are twice as many shared electrons.

Reactivity

The difference between the reactivity of these two types is determined by how many pi (π) bonds they have. Which can either be single or double in nature depending on whether they are aliphatic or aromatic molecules. Since aromatics always contain at least one π bond per molecule, their chemical behavior tends to be less reactive because this feature makes them electron-deficient species due to resonance effects that increase stability while also decreasing electrophilicity.

Naming differences

The difference in the way these two types are named also plays a big role since aliphatic compounds usually have simpler, shorter names with just straight-chain structures and numbers denoting how many carbons they contain. For example, Methane, Ethane, propane, etc., while aromatics tend to be more complex as they include their number of carbon atoms followed by one or two letters that represent rings present plus generic terms like Methylbenzene, Naphthalene, Phenanthrene.

Difference in odour

The difference in their odor is another key factor since aliphatic hydrocarbons usually have an unpleasant odour while aromatic ones tend to be fragrant. This occurs because of the presence of π bonds that are responsible for aromatics having a planar structure. Also with delocalized electrons then allow them to engage in resonance interactions that result in these molecules forming strong, covalent connections with olfactory receptors where they can attach and give off any kind of smell depending on what else is present within an environment.

Comparison Chart: Aliphatic Vs Aromatic Hydrocarbons

ParametersAliphaticAromatic
Open chain compoundsYesNo
Boiling pointsLowerHigher
OdourUnpleasantPleasant
NamesSimplerComplicated
ExamplesMethaneMethlybenzene

The similarity between the two hydrocarbons

Both types of hydrocarbons consist entirely of hydrogen and carbon molecules only bonded together by covalent bonds. Another similarity is that both can have a closed chain or open-chain structure.

Conclusion

The difference between aliphatic and aromatic hydrocarbons is their chemical structure. Aliphatics are linear molecules with a high carbon-to-hydrogen ratio. While aromatics have a ringed molecular shape which makes them more reactive than the former. This means that they will react faster to other substances in order to form bonds. In general, these reactions can involve polymerization or combustion if enough energy is present. Meaning that they're often used as fuels for heating or transportation purposes. That's all there really is to it! Now you'll know how different types of hydrocarbons differ from one another when you come across them in your chemistry readings.

References

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About the Author: Nicolas Seignette

Nicolas Seignette, who holds a scientific baccalaureate, began his studies in mathematics and computer science applied to human and social sciences (MIASHS). He then continued his university studies with a DEUST WMI (Webmaster and Internet professions) at the University of Limoges before finishing his course with a professional license specialized in the IT professions. On 10Differences, he is in charge of the research and the writing of the articles concerning technology, sciences and mathematics.
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