07Nov 2016 by Vincent Summers 4 Comments

Aromatic Resonance – What It Is and What It Is Not

Chemistry
[caption id="attachment_19938" align="alignright" width="440"] Prominent resonance structures.[/caption] Sometimes a chemistry or physics concept is misunderstood even by the reader of above-average intelligence and education. Such is the case with the chemist’s use of the term aromatic resonance. There are a small number of recognized rules for aromatic behavior. These include: cyclic geometery planarity 4n + 2 contributing, de-localized, conjugated (π) double bonds An Example of What Aromatic Resonance Is Not The best and oldest known example is benzene, C₆H₆. Benzene is cyclic (one ring), planar (flat), and has 6 delocalized, conjugated double bonds. Frequently, the organic chemist simply renders benzene’s structure… There is a carbon atom at each vertex of the hexagonal ring. Attached to each carbon and pointing outward from it is one hydrogen atom. Now each carbon atom…
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16Nov 2014 by Vincent Summers 1 Comment

The Zwitterion – Nature, Occurrence, Ongoing Research

Chemistry
What in the world is a zwitterion? What is its importance? Molecules are bonded atoms that act as a unit. They are electrically balanced. This means they contain a total number of electrons equal to the number of protons. If a chemical structure does not possess an equal number of electrons and protons it is an ion. Molecules as a unit are electrically neutral. However, there may be local charges due to geometry or electronegativity. These charges are mostly less than that of a proton or electron. There is an exception. It is the zwitterion. This kind of ion has a full positive and a full negative charge. In organic chemistry there may be an alkyl backbone consisting of carbon (C) and hydrogen (H). Other groups (pendant groups) include hydroxyl,…
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23Mar 2014 by Vincent Summers No Comments

The Quintessential Aromatic Hydrocarbon Benzene (Pt.2)

Chemistry
[caption id="attachment_6069" align="alignright" width="440"] Benzene De-localized Pi-system - CCA Share Alike 3.0 Unported by Vladsinger[/caption] In Part One of The Quintessential Aromatic Hydrocarbon Benzene, we saw that the so-called 1,3,5-cyclohexatriene was really not completely described by the structure that that name implies. It is equivalent to 2,4,6-cyclohexatriene (if you flip the 1,3,5- structure over, and you get the 2,4,6- structure), and includes a variety of other contributing factors. Although we did not list them, they may include ionic contributors.1 In general, these are discounted. Visualizing Benzene's Structure The conclusion is that the compound actually has six equivalent bonds between adjacent carbon atoms, forming six internal angles angle each equal to 60°. The bonds are each, then, “single-and-one-half” bonds between each carbon pair. The molecule is flat, even as a collection…
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