Delocalized electron: Difference between revisions

Jump to navigation Jump to search
No edit summary
m (Bot: Automated text replacement (-{{SIB}} + & -{{EH}} + & -{{EJ}} + & -{{Editor Help}} + & -{{Editor Join}} +))
 
Line 1: Line 1:
[[Image:Benz4.png|right|Benzene, with the delocalization of the electrons indicated by the circle.]]  
[[Image:Benz4.png|right|Benzene, with the delocalization of the electrons indicated by the circle.]]  
{{EH}}
 
{{SI}}
{{SI}}


Line 19: Line 19:
[[Category:Electron]]
[[Category:Electron]]


{{SIB}}
 
{{WikiDoc Sources}}
{{WikiDoc Sources}}


{{WH}}
{{WH}}

Latest revision as of 00:33, 9 August 2012

Benzene, with the delocalization of the electrons indicated by the circle.
Benzene, with the delocalization of the electrons indicated by the circle.

WikiDoc Resources for Delocalized electron

Articles

Most recent articles on Delocalized electron

Most cited articles on Delocalized electron

Review articles on Delocalized electron

Articles on Delocalized electron in N Eng J Med, Lancet, BMJ

Media

Powerpoint slides on Delocalized electron

Images of Delocalized electron

Photos of Delocalized electron

Podcasts & MP3s on Delocalized electron

Videos on Delocalized electron

Evidence Based Medicine

Cochrane Collaboration on Delocalized electron

Bandolier on Delocalized electron

TRIP on Delocalized electron

Clinical Trials

Ongoing Trials on Delocalized electron at Clinical Trials.gov

Trial results on Delocalized electron

Clinical Trials on Delocalized electron at Google

Guidelines / Policies / Govt

US National Guidelines Clearinghouse on Delocalized electron

NICE Guidance on Delocalized electron

NHS PRODIGY Guidance

FDA on Delocalized electron

CDC on Delocalized electron

Books

Books on Delocalized electron

News

Delocalized electron in the news

Be alerted to news on Delocalized electron

News trends on Delocalized electron

Commentary

Blogs on Delocalized electron

Definitions

Definitions of Delocalized electron

Patient Resources / Community

Patient resources on Delocalized electron

Discussion groups on Delocalized electron

Patient Handouts on Delocalized electron

Directions to Hospitals Treating Delocalized electron

Risk calculators and risk factors for Delocalized electron

Healthcare Provider Resources

Symptoms of Delocalized electron

Causes & Risk Factors for Delocalized electron

Diagnostic studies for Delocalized electron

Treatment of Delocalized electron

Continuing Medical Education (CME)

CME Programs on Delocalized electron

International

Delocalized electron en Espanol

Delocalized electron en Francais

Business

Delocalized electron in the Marketplace

Patents on Delocalized electron

Experimental / Informatics

List of terms related to Delocalized electron

Overview

In chemistry delocalized electrons are electrons in a molecule that are not associated with a single atom or to a covalent bond. Delocalized electrons are contained within an orbital that extends over several adjacent atoms. Classically, delocalized electrons can be found in conjugated systems of double bonds and in aromatic and mesoionic systems. A case of delocalized electrons occurs also in solid metals, where the d-subshell interferes with the above s-subshell, and contributes to the properties of a metal. It is increasingly appreciated that electrons in sigma bonding levels are also delocalized. For example, in methane, the bonding electrons are shared by all five atoms equally. Pervasive existence of delocalization is implicit in Molecular Orbital Theory.

In the simple aromatic ring of benzene the delocalization of six π electrons over the C6 ring is often graphically indicated by a circle. The fact that the six C-C bonds are equidistant is one indication of this delocalization. In Valence Bond Theory, delocalization in benzene is represented by resonance structures.

Another example of a delocalized electrons can be found in a carboxylate group, wherein the negative charge is centered equally on the two oxygen atoms.

Delocalized electrons are important for several reasons. One, an expected chemical reaction may not occur because the electrons delocalize to a more stable configuration, resulting in a reaction that happens at a different location. An example attempting the Fridel-Crafts alkylation of benzene with 1-chloro-2-methylpropane; the carbocation rearranges to a tert-butyl group stabilized by hyperconjugation, a particular form of delocalization.

Delocalized electrons also exist in the structure of metals. Metallic structure consist of aligned positive ions (cations) in a "sea" of delocalized electrons. This means that the electrons are free to move throughout the structure, and gives rise to properties such as conductivity.

In diamond all four outer electrons of each carbon atom are 'localized' between the atoms in covalent bonding. The movement of electrons is restricted and diamond does not conduct an electric current. In graphite, each carbon atom uses only 3 of its 4 outer energy level electrons in covalently bonding to three other carbon atoms in a plane. Each carbon atom contributes one electron to a delocalized system of electrons that is also a part of the chemical bonding. The delocalized electrons are free to move throughout the plane. For this reason, graphite conducts electricity along the planes of carbon atoms, but does not conduct in a direction at right angles to the plane.


Template:WikiDoc Sources

Template:WH