Greetings and Happy New Year!,
This post is on disubstituted benzene compounds using diamines as specific examples. There are exactly three orientations for two functional groups, relative to each other, on a benzene ring; ortho, meta, and para. Ortho groups are adjacent, meta groups are separated by one carbon atom and para groups are on opposite sides of the ring.
The three phenylenediamine structures, designated as ortho, meta, and para are isomers because their chemical formulas are identical; C6H4(NH2)2. All three structures are separate compounds with their own distinct physical and chemical properties. Amino groups are said to be activating when attached to a benzene ring. This is connected with the ability of Nitrogen to donate a pair of electrons to the benzene pi-bond system. The net result is an ortho/para directing action toward additional groups added to the benzene ring, with an overall increase in rate of reaction.* In the case of our three diamine examples, it is only the meta isomer which can be both ortho and para directing: Do you see why?
The following graphic illustrates the differences between the three isomers using ball-and-stick models.
That's all for this post. As always, thank you for reading!
*https://en.wikipedia.org/w/index.php?title=Electrophilic_aromatic_substitution&oldid=695513616
A Publication of http://ExcellenceInLearning.biz
This post is on disubstituted benzene compounds using diamines as specific examples. There are exactly three orientations for two functional groups, relative to each other, on a benzene ring; ortho, meta, and para. Ortho groups are adjacent, meta groups are separated by one carbon atom and para groups are on opposite sides of the ring.
The three phenylenediamine structures, designated as ortho, meta, and para are isomers because their chemical formulas are identical; C6H4(NH2)2. All three structures are separate compounds with their own distinct physical and chemical properties. Amino groups are said to be activating when attached to a benzene ring. This is connected with the ability of Nitrogen to donate a pair of electrons to the benzene pi-bond system. The net result is an ortho/para directing action toward additional groups added to the benzene ring, with an overall increase in rate of reaction.* In the case of our three diamine examples, it is only the meta isomer which can be both ortho and para directing: Do you see why?
The following graphic illustrates the differences between the three isomers using ball-and-stick models.
That's all for this post. As always, thank you for reading!
*https://en.wikipedia.org/w/index.php?title=Electrophilic_aromatic_substitution&oldid=695513616
A Publication of http://ExcellenceInLearning.biz
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