The key difference between haloalkanes and haloarenes is that haloalkanes are aliphatic compounds containing halogens, whereas haloarenes are aromatic compounds containing halogens.
Halogens are the group 7 chemical elements which include fluorine (F), chlorine (Cl), bromine (Br), iodine (I) and astatine (At). When these halogens combine with organic compounds, we name them as halo compounds. Haloalkanes and haloarenes are two types of halo compounds.
CONTENTS
1. Overview and Key Difference
2. What are Haloalkanes
3. What are Haloarenes
4. Side by Side Comparison – Haloalkanes vs Haloarenes in Tabular Form
6. Summary
What are Haloalkanes?
Haloalkanes are a group of organic compounds comprising alkanes combined with halogens. There can be one or more halogens in the same compound. Also, another common name for these compounds is alkyl halides. These molecules do not contain any aromatic ring.
In the classification of these compounds, we can classify them according to the structure and the type of halogen. According to the structure, there are primary, secondary and tertiary haloalkanes. In primary haloalkanes, the carbon atom connected to the halogen atom is only attached to one other alkyl group whereas for secondary haloalkanes, the carbon atom connects with two other alkyl groups and in tertiary haloalkanes, there are three alkyl groups. When classifying these compounds according to the halogen atom, we can name them as organofluorine, organochlorine, organobromine and organoiodine.
Figure 01: Chloromethane
Generally, haloalkanes resemble the properties of parent alkanes; colourless, odourless, hydrophobic, etc. However, their melting and boiling points are higher than parent alkanes. It is because of the strong intermolecular forces between molecules; the carbon-halogen bond is polar, and thus, the molecules have polar-polar interactions.
When considering the production of the haloalkanes, we can produce them from alkanes via free radical halogenation, from alkenes and alkynes, from alcohols, from carboxylic acids, etc. Apart from that, haloalkanes tend to undergo substitution and elimination reactions.
What are Haloarenes?
Haloarenes are a group of organic compounds containing aromatic compounds which have one or more halogen atoms. Also, another common name for these compounds is aryl halides. More importantly, one or more halogen atoms in these compounds directly bind with an aromatic ring. The most common and important members of this group are aryl chlorides.
Figure 02: Benzyl Chloride
The two common methods of production are direct halogenation of aromatic rings and Sandmeyer reaction in which aniline is converted into diazonium salt using nitrous acid. When considering the reaction these compounds undergo, they take part in the benzyne mechanism, which gives aniline and they are also important in organometallic reagent formation.
What is the Difference Between Haloalkanes and Haloarenes?
Haloalkanes are a group of organic compounds comprising alkanes combined with halogens. Haloarenes are a group of organic compounds comprising aromatic compounds which has one or more halogen atoms. The key difference between haloalkanes and haloarenes is that haloalkanes are aliphatic compounds containing halogens, whereas haloarenes are aromatic compounds containing halogens.
Furthermore, haloalkanes have no aromatic rings, but haloarenes have. Haloalkanes can be produced from alkanes via free radical halogenation, from alkenes and alkynes, from alcohols, from carboxylic acids, etc. However, the two common production methods for haloarenes are direct halogenation of aromatic rings and Sandmeyer reaction. Therefore, this is another major difference between haloalkanes and haloarenes.
Below info-graphic shows more side by side comparisons related to the difference between haloalkanes and haloarenes.
Summary – Haloalkanes vs Haloarenes
Haloalkanes and haloarenes are organic compounds. The key difference between haloalkanes and haloarenes is that haloalkanes are aliphatic compounds containing halogens, whereas haloarenes are aromatic compounds containing halogens.
Reference:
1. “Haloalkanes and Haloarenes – Definition, Classification, Uses.” BYJUS, Byju’s, 8 Apr. 2019, Available here.
Image Courtesy:
1. “Methyl Chloride” By Yikrazuul – Own work (Public Domain) via Commons Wikimedia
2. “Benzyl chloride” By Edgar181 – Own work (Public Domain) via Commons Wikimedia