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Topic: Electrophilic aromatic substitution

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	Electrophilic aromatic substitution - Wikipedia, the free encyclopedia
		Electrophilic aromatic substitution or EAS is an organic reaction in which an atom, usually hydrogen, in an aromatic system is replaced by an electrophile.
		Other electrophiles are aromatic diazonium salts in diazonium couplings, carbon dioxide in the Kolbe-Schmitt reaction and activated carbonyl groups in the Pechmann condensation.
		Examples of electrophilic substitutions to pyrrole are the Pictet-Spengler reaction and the Bischler-Napieralski reaction.
	en.wikipedia.org /wiki/Electrophilic_aromatic_substitution (1146 words)

	Electrophilic substitution - Wikipedia, the free encyclopedia
		Electrophilic substitution reactions are chemical reactions in which an electrophile displaces another group, typically but not always hydrogen.
		Electrophilic aromatic substitution is an important way of introducing functional groups on benzene rings.
		In electrophilic substitution in aliphatic compounds an electrophile displaces a functional group.
	en.wikipedia.org /wiki/Electrophilic_substitution (188 words)

	Aromatic Reactivity
		This activation or deactivation of the benzene ring toward electrophilic substitution may be correlated with the electron donating or electron withdrawing influence of the substituents, as measured by molecular dipole moments.
		For example, electrophilic chlorination of toluene occurs hundreds of times faster than chlorination of benzene, but the relative rates are such that the products are 60% ortho-chlorotoluene, 39% para and 1% meta-isomers, a ratio similar to that observed for nitration.
		A practical concern in the use of electrophilic aromatic substitution reactions in synthesis is the separation of isomer mixtures.
	www.cem.msu.edu /~reusch/VirtualText/benzrx1.htm (2788 words)

	Electrophilic Aromatic Substitution
		In electrophilic aromatic substitution, the benzene ring acts as an electron donor (Lewis base or nucleophile) and reacts with an electron acceptor (Lewis acid or electrophile).
		In nucleophilic aromatic substitution, halogens are substituted by a nucleophile only if the aryl halides have electron-withdrawing groups in a position ortho or para to the halogen.
		Electrophilic substitutions are favored by electron-donating groups which stabilize the carbocation intermediate.
	www.chem.latech.edu /~deddy/chem252/EAS.htm (1241 words)

	Electrophilic aromatic substitution - Encyclopedia, History, Geography and Biography
		It has been proposed that this article or section be merged with Electrophilic substitution.
		These compounds undergo aromatic electrophilic substitution reactions under much milder conditions.
		Electrophilic aromatic substitution and Five membered heterocyclic compounds.
	www.arikah.net /encyclopedia/Electrophilic_aromatic_substitution (170 words)

	Structure of Benzene
		The reagent - catalyst - electrophile - product pattern works well when the aromatic compound is benzene itself, but things become more complicated when a substituted benzene (a molecule in which one of the hydrogens of benzene has been replaced by another atom or group) is used.
		Electrophilic attack will be faster at positions such that the carbocations produced have positive charges on carbons which are bonded to electron donating groups like methy groups.
		The underlying idea in the forgoing analysis of directive effects in electrophilic was understanding the relative rates of reaction when the competition was between different sites in the same molecule.
	chemistry2.csudh.edu /rpendarvis/ElAromSubst.html (1495 words)

	Method for the preparation of noncaking coals from caking coals by means of electrophilic aromatic substitution - ...
		The process according to claim 1 wherein the electrophilic aromatic substitution reaction practiced on the coal comprises alkylation.
		The process of claim 1 wherein the electrophilic aromatic substitution reaction step practiced on the coal is conducted in the presence of a catalyst.
		In general, the electrophilic aromatic substitution reaction practiced on the subject coal constitutes either alkylation or acylation.
	www.freepatentsonline.com /4059410.html (3121 words)

	Electrophilic Aromatic Substitution (Site not responding. Last check: 2007-10-21)
		Electrophillic aromatic substitution is influenced by the group Q as follows:
		Electron withdrawing substituents form two very unstable resonance structures, one occurring when substitution is ortho and one when substitution is para to the releasing substituent.
		The intermediate benzenonium ion resulting from ortho and para attack is further stabilized by a fourth resonance structure when the activating substituent in an amine group, an alkoxy group or an hydroxide group.
	webpages.charter.net /markbishop/Organic/Aromatic%20hydrocarbons.htm (206 words)

	Method for improving gasification process rates and yields by means of electrophilic aromatic substitution pretreatment ...
		Coal is electrophilically aromatically substituted (i.e., alkylated or acylated) in the presence of an alkylating or acylating agent with or without a catalyst under mild conditions to give a treated coal product.
		This is in contradistinction with the behavior which we have observed with the Illinois coal which, upon alkylation, had somewhat higher reactivities (40-50% higher) and indicates that all coals are not equivalent insofar as their ability to benefit from electrophilic aromatic substitution pretreatment in the case of gasification.
		The electrophilically aromatically substituted coal is heated to the desired maximum temperature (from the starting point of ambient room temperature) at a rate of from 0.1.degree.
	www.freepatentsonline.com /4072475.html (5599 words)

	An Organization Device for Visualizing Mechanisms and Regiochemistry Rationales in Electrophilic Aromatic Substitution
		One sheet is placed over the other in order to visualize the mechanism between the substituted aromatic compound selected and the chosen reagent.
		The two aspects are (1) the substitution itself, including the identity of the electrophile, the reagent(s) needed to generate it, and the substituent in the product and (2) the electronic effects of the groups in the aromatic compounds upon the intermediate(s) and the structure of the product.
		The effect of the use of the Electrophilic Aromatic Substitution Tool (also known as EAS-at-a-Glance) on the test performance of students enrolled in undergraduate organic chemistry was determined by a post-test-only control-group study.
	chemeducator.org /bibs/0006003/630142dn.htm (283 words)

	Electrophilic Aromatic Substitution
		Groups that donate electron density (alkyls, those with a lone pair at the point of attachment, those with less electronegative atoms connected to the atom of attachment) stabilize the carbocation intermediate that is formed during ortho and para electrophilic aromatic substitution, so these positions are favored.
		There is no extra stability associated with the carbocation intermediate that is formed during meta substitution, so this position is not favored.
		While halogens are o,p directors their electronegativity makes them “deactivators” towards electrophilic aromatic substitution.
	www.uwlax.edu /faculty/czerwinski/eas2.htm (451 words)

	Organic II Quiz 2 Page (Site not responding. Last check: 2007-10-21)
		Organic Chemistry II Quiz #1: Benzene and Aromaticity
		A) highly deactivated aromatic rings are unreactive under Friedel-Crafts conditions.
		B) over-alkylation of the ring is a distinct possibility.
	www.chemistry.ccsu.edu /glagovich/teaching/311/quiz/quiz4/quiz2.html (240 words)

	Electrophilic Aromatic Substitution (Site not responding. Last check: 2007-10-21)
		The objective of this exercise is to explain the observed effects of ortho-para and meta directing substituents of electrophilic aromatic substitution in terms of the partial charge on each aromatic carbon atom.
		Similarly, determine whether -CH is ortho-para directing or meta-directing substituent for electrophilic aromatic substitution.
		Thus, these positions become activated towards electrophilic aromatic substitution, and the CH group is an ortho-para director, as we learned in organic chemistry.
	www.webmo.net /curriculum/eas/eas_key.html (226 words)

	C 2131 Electrophilic Aromatic Substitution Reactions
		The characteristic reactions of aromatic compounds are the electrophilic aromatic substitution reactions.
		The major differences are that the electrophile involved must be a very strong electrophile (very electron deficient) and that the aromatic ring must be regenerated in the final step of the reaction.
		to regenerate the aromatic ring one of the Br atoms from the complex removes the proton from the carbon that received the original Br, and the electrons from the C-H bond regenerate the aromatic sextet.
	www.mta.ca /~acockshu/c2131aromsubst.html (1395 words)

	Ch12 : Electrophilic Aromatic Substitution
		The structure and properties of aromatic systems were discussed in Chapter 11.
		Aromatic because the reaction is characteristic of aromatic systems.
		Electrophilic aromatic substitution reactions are the very important class of reactions that allow the introduction of substituents onto arenes.
	www.chem.ucalgary.ca /courses/351/Carey5th/Ch12/ch12-0.html (112 words)

	SONOMA STATE UNIVERSITY
		Any modern Organic Chemistry text book will give a complete discussion of the currently accepted mechanism of electrophilic aromatic substitution reactions including both the directive influence of substituents and the ring activating or deactivating effects of these substituents.
		In this experiment you will use GLPC to study the products of the bromination of benzene and substituted aromatic compounds such as toluene or chlorobenzene.
		The major emphasis of your laboratory report should be the analysis of the results of your experiment in terms of what you were and were not able to determine in terms of the nature of this reaction.
	www.sonoma.edu /users/t/trowbrda/336/elec-arom-sub.html (1016 words)

	Articles - Organic reaction (Site not responding. Last check: 2007-10-21)
		The basic organic chemistry reaction types are addition reactions, elimination reactions, substitution reactions, rearrangement reactions and organic redox reactions.
		electrophilic addition or EA nucleophilic addition or NA radical addition or RA Elimination reactions
		electrophilic substitution or ES electrophilic aromatic substitution or EAS
	www.beadscenter.com /articles/Organic_reaction (537 words)

	Electrophilic Aromatic Substitution (Site not responding. Last check: 2007-10-21)
		The common explanation for the substituent effect in electrophilic aromatic substitution, is based on the relative stability of the intermediates, which are close to the transition state.
		This, in turn, is founded on the accommodation of the positive charge by the substituents.
		On the left it is seen how mesomeric electron donors at the o/p positions stabilize the intermediate, and thereby enhance the reaction.
	cheminf.cmbi.ru.nl /wetche/organic/eas/charexpl.html (125 words)

	ELECTROPHILIC AROMATIC SUBSTITUTION: (Site not responding. Last check: 2007-10-21)
		Electrophilic aromatic substitution (EAS) is one of the primary methods for functionalizing aromatic rings.
		A wide variety of EAS reactions exist and the one you will be studying in this lab is nitration (see pp 576-7 in your text, there is a cool animation of this reaction at: www.cm.utexas.edu/groups/iverson/eashm2.htm).
		Two substituted aromatic rings will be nitrated: veratrole and methyl benzoate.
	web.centre.edu /hskncht/pastcourses/che341_lab_f04/NITRATIONLAB.htm (603 words)

	JCE 2005 (82) 616 [Apr] A Green Starting Material for Electrophilic Aromatic Substitution for the Undergraduate Organic ...
		Substitution of alternative green procedures wherever possible reduces organic waste and allows students to consider the need for environmentally sound chemistry.
		A green electrophilic aromatic substitution reaction (EAS), nitration of tyrosine, has been developed for use in the undergraduate laboratory.
		This reaction allows students to consider the varied aspects of EAS including activating and deactivating groups and o, p, m directors in a green environment.
	www.jce.divched.org /Journal/Issues/2005/Apr/abs616.html (301 words)

	Practice Questions For Chapter 16 - EMOC (Site not responding. Last check: 2007-10-21)
		Question 1 - question testing your knowledge of the directing effects of substituents on the benzene ring towards electrophilic aromatic substitution.
		Question 3 - question testing your ability to synthesize poly-substituted benzenes using electrophilic aromatic substitution.
		These pages may be downloaded and linked from other pages freely for academic and educational purposes.
	www.cem.msu.edu /~parrill/ch16 (100 words)

	Electrophilic Aromatic Substitution (Site not responding. Last check: 2007-10-21)
		Electrophilic Aromatic Substitution: The aromatic ring is very electron rich, bu...
		JCE 2004 (81) 644 [May] The Electrophilic Aromatic Substitution of Fluorobenzene...
		Lab 9 - Electrophilic Aromatic Substitution of Acetanilide...
	www.scienceoxygen.com /chem/113.html (69 words)

	JCE 2004 (81) 644 [May] The Electrophilic Aromatic Substitution of Fluorobenzene
		In the June 2003 issue, Joel Rosenthal and David Schuster published a paper entitled “The Anomalous Reactivity of Fluorobenzene in Electrophilic Aromatic Substitution and Related Phenomena” (1).
		The authors and the reviewers, apparently, were not aware of my publication in this Journal in 1966 entitled “The Activating Effect of Fluorine in Electrophilic Aromatic Substitution” (2).
		In that paper I referred to four electrophilic aromatic substitution reactions in which the para position of fluorobenzene was more reactive than any one position of benzene, and indicated that those and three additional reactions are discussed in a paper by Leon Stock and H. Brown (3).
	www.jce.divched.org /Journal/Issues/2004/May/abs644_2.html (303 words)

	[No title] (Site not responding. Last check: 2007-10-21)
		Arylamines are potentially very reactive towards electrophilic aromatic substitution
		Steric effects in the amide also often lead to a decrease in the amount of the ortho-products.
		In principle, the sequence protect - substitute - deprotect is equivalent to being able to susbtitute the aniline directly.
	www.mhhe.com /physsci/chemistry/carey/student/olc/graphics/carey04oc/ref/ch22arylamines.html (174 words)

	Organic Chemistry Outlines
		Substitution and dehydration reactions of alcohols, substitutions of sulfonate esters of ethers reactions of epoxides, organometallic compounds
		Nomenclature of substituted benzenes and review of bonding in benzene Reactivity considerations, general methanism for clectrophific aromatic substitution reiactions Halogenation of benzene.
		The laboratory consists of experiments that illustrate the properties of organic compounds and the techniques used to investigate and produce organic materials.
	www.admissions.med.ubc.ca /orgchem.htm (2007 words)

	Electrophilic Aromatic Substitution (Site not responding. Last check: 2007-10-21)
		The aromatic system of benzene and other aromatics can act as a nucleophile to attack an electrophile, in this example 'E'.
		The cationic intermediate can be stabilised by delocalisation of the positive charge around the six membered ring.
		The rate determining step of the reaction is commonly the formation of the cationic intermediate.
	www.chem.ox.ac.uk /vrchemistry/nor/notes/eas.htm (62 words)

	Rates of Electrophilic Aromatic Substitution Prelab (Site not responding. Last check: 2007-10-21)
		A pair of Chemistry 320 students ran a bromination reaction of diphenylether, and found that the bromine color had disappeared by the time they got the cuvet into the spectrophotometer.
		The relative rates of electrophilic aromatic substitution for the three starting materials would be.....
		Below is a space for your thoughts, including general comments about today's assignment (what seemed impossible, what reading didn't make sense, what we should spend class time on, what was "cool", etc.):
	143.206.107.71 /www/chemistry/organic/EASRatesPreLab.htm (214 words)

	Electrophilic Aromatic Substitution (Site not responding. Last check: 2007-10-21)
		Each EAS reaction will have one or more pre-steps in which a sufficiently electrophilic species is generated.
		The electrophile for the reaction is shown in the lower left-hand corner of the slide.
		Direct suggestions, comments, and questions about this page to Arlene Courtney, courtna@wou.edu.
	www.wou.edu /las/physci/ch335/lecture/lect14.htm (44 words)

	Electrophilic Aromatic Substitution (Site not responding. Last check: 2007-10-21)
		Electrophilic aromatic substitution generally takes the following form.
		Step 1: Attack of benzene on the electrophile to form resonance stabilized carbocation
		Notes: Formation of the carbocation, the rate-determining step, is highly endothermic because it forms a nonaromatic carbocation.
	www.cartage.org.lb /en/themes/Sciences/Chemistry/Organicchemistry/CommonReaction/ElectrophilicAromatic/ElectrophilicAromatic.htm (63 words)

	[No title] (Site not responding. Last check: 2007-10-21)
		We know that some groups activate the benzene ring toward electrophilic substitution and other groups deactivate it.
		The substituents on the benzene ring also affect the site of attack of the incoming electrophile.
		Optimize the geometries and calculate the energies at the AM1 level for benzene, toluene, nitrobenzene and aniline.
	www.oc.chalmers.se /spartanc/electrophilic.html (112 words)

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