Difference Between Aliphatic and Aromatic Hydrocarbons

Key Difference – Aliphatic vs Aromatic Hydrocarbons

Let us first briefly see whathydrocarbons正在讨论脂肪族和芳烃之间的差异。碳氢化合物是其结构中含有碳和氢原子的有机化合物。这key differencebetween aliphatic and aromatic hydrocarbons is,aliphatic hydrocarbons do not contain aconjugatedsystem of bondwhereasaromatic hydrocarbons contain a conjugated bond system.However, both of these molecules are considered asorganic compounds.

What areAliphatic Hydrocarbons?

Aliphatic hydrocarbons are the organic molecules containing Carbon (C) and Hydrogen (H) atoms in their structure; in straight chains, branched chains or non-aromatic rings. Aliphatic hydrocarbons can be categorized into three main groups; alkanes,烯烃和炔烃.

What areAromatic Hydrocarbons?

Aromatic hydrocarbons are sometimes known as “arenes“ 或者 ”aryl hydrocarbons”. Most aromatic hydrocarbons contain a苯在其结构中响起；但是有非苯芳香烃称为heteroarenes, which follow the “Huckle’s rule” (Cyclic rings which follow the Huckle’s规则have 4n+2 number of π-electrons; where n=0,1,2,3,4,5,6). Some aromatic hydrocarbons have more than one ring; they are calledpolycyclic aromatic hydrocarbons.

What is the difference between Aliphatic and Aromatic Hydrocarbons?

脂肪族和芳烃的结构

Aliphatic Hydrocarbons:它们的结构中有直链，分支链或非芳香环。该组具有饱和和不饱和的烃。烷烃是saturated hydrocarbons，烯烃和炔烃是不饱和烃。

直链：

Octane

Branded Chains:

5-ethyl-3-methyloctane

2-methyl-3-pentence

非芳香环：

Aromatic Hydrocarbons:Aromatic hydrocarbons have aromatic ring system in their structure. They are all unsaturated hydrocarbons, but relatively stable due to the conjugated bond system.

Categories of Aliphatic and Aromatic Hydrocarbons

Aliphatic Hydrocarbons:

这re are three main groups in aliphatic hydrocarbons; alkanes, alkenes and alkynes. They are also known as烯丙基烃.

Alkanes:In alkanes, Carbon and Hydrogen atoms are bonded together by single bonds. They do not have multiple bonds. Alkanes form ring structures, they are called cycloalkanes.

Alkenes: This group contains bothsingle and double bondsbetween Carbon atoms. Hydrogen and Carbon atoms always form single bonds.

Alkynes:Alkynes have triple bonds between Carbon atoms in addition to single bonds.

Aromatic Hydrocarbons:

大多数芳族烃的结构中至少包含一个苯环。但是很少有非偶氮芳族烃，它们被称为“杂种”。芳族碳氢化合物称为“芳基”烃。

Biphenyl (An aromatic hydrocarbon with two benzene rings)

Bonding Pattern of Aliphatic and Aromatic Hydrocarbons

Aliphatic Hydrocarbons:

In aliphatic hydrocarbons; single, double or triple bonds can exist anywhere in the molecule. Sometimes, there can be several structures for one molecular formula by changing the position of the multiple bond(s). These molecules have a localized electron system.

Aromatic Hydrocarbons:

In aromatic hydrocarbons, they have an alternative single and double bond system to form a conjugated bond system to delocalize some electrons. (Delocalized electrons can move from one bond to another).

Reactions of Aliphatic and Aromatic Hydrocarbons

Aliphatic Hydrocarbons:

Saturated hydrocarbonsundergo substitution reactions; unsaturated hydrocarbons attain the stability by addition reaction. But, some reactions happen under controlled conditions without breaking multiple bonds.

Aromatic Hydrocarbons:

Aromatic hydrocarbons are unsaturated, but have a stable conjugated electron system, so that they are more liable to substitution reactions rather than addition reactions.

Image Courtesy:

“Polycyclic Aromatic Hydrocarbons” by Inductiveload – Own work by uploader, Accelrys DS Visualizer. (Public Domain) viaCommons