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Topic: Elimination reaction

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 E1cB elimination reaction - Wikipedia, the free encyclopedia
The E1cB elimination reaction is a special type of elimination reaction in organic chemistry.
This reaction mechanism explains the formation of alkenes from (mostly) alkyl halides through a carbanion intermediate given specified reaction conditions and specified substrates.
Being able to distinguish between different elimination reaction mechanisms (E2, E1, E1cB) is often difficult and involves the study of chemical kinetics, kinetic isotope effects, substituent effects and computational chemistry.
en.wikipedia.org /wiki/E1cB_elimination_reaction   (380 words)

 Elimination - Wikipedia, the free encyclopedia
In chemistry, an elimination reaction is a one- or two-step organic reaction in which two functional groups combine to form a larger organic product with a new bond such as an ester, amide, or ether.
In pharmacology, elimination (or clearance) refers to all the processes that remove a drug or other foreign agent from the body.
Eliminator is ZZ Top's 8th studio album, released in 1983.
en.wikipedia.org /wiki/Elimination   (190 words)

 Alcohol - Wikipedia, the free encyclopedia
The deprotonation reaction to produce an alkoxide salt is either performed with a strong base such as sodium hydride or n-butyllithium, or with sodium or potassium metal.
In the Barton-McCombie deoxygenation an alcohol is deoxygenated to an alkane with tributyltin hydride or a trimethylborane -water complex in a radical substitution reaction.
Esters may also be prepared by reaction of the alcohol with an acid chloride in the presence of a base such as pyridine.
en.wikipedia.org /wiki/Alcohol   (2770 words)

 Carbonyl Reactivity
The fundamental transformation in this reaction is a dimerization of an aldehyde (or ketone) to a beta-hydroxy aldehyde (or ketone) by alpha C–H addition of one reactant molecule to the carbonyl group of a second reactant molecule.
The acid-catalyzed elimination of water is not exceptional, since this was noted as a common reaction of alcohols.
The exception, reaction #3, is conducted under mild conditions with an excess of the reactive aldehyde formaldehyde serving in the role of electrophilic acceptor.
www.cem.msu.edu /~reusch/VirtualText/aldket2.htm   (3411 words)

 Reaction Between Sodium Hydroxide
A neutralisation reaction between hydrochloric acid and sodium hydroxide is...
the aqueous neutralization reaction between acetic acid and sodium hydroxide is different from that for the reaction between hydrochloric acid and sodium hydroxide.
One of the first reactions students learn about in an introductory chemistry course is the acid-base reaction between hydrochloric acid and sodium hydroxide, Equation 1.
sodiumhydroxide.moatsodium.com /reactionbetweensodiumhydroxide   (789 words)

 Encyclopedia :: encyclopedia : Organic chemistry   (Site not responding. Last check: 2007-10-21)
Organic chemistry is the scientific study of the structure, properties, composition, reactions, and synthesis of organic compounds that by definition contain carbon.
It is presumed that functional group F is bonded to one of the carbon atoms in R. R is often one of the hydrocarbon categories mentioned previously.
The example above is a substitution reaction, since Y is substituted for F. Important concerns of a reaction include whether it will occur spontaneously determined by the Gibb's free energy, what heat is produced or needed in terms of Enthalpy and what unintended products are formed as well.
www.hallencyclopedia.com /Organic_chemistry   (1219 words)

 [No title]
In both the nucleophilic substitution reaction and the elimination reaction, which only a single particle, a molecule of the halide, is undergoing a change in covalence in the rate-determining step (3).
In the substitution reaction, it is postulated that hydroxide ion attacks the halogen-bearing carbon atom as the halide ion is simultaneously liberated.
In the bimolecular elimination reaction, according to the proposed mechanism, the hydroxide ion removes a B-hydrogen as a proton, with synchronous shift of an electron pair and elimination of the halide ion to form the corresponding olefin.
www.unf.edu /~jpradhan/hydrls2.htm   (1536 words)

 [No title]
Elimination reactions are important as a method for the preparation of alkenes.
In many cases the elimination reaction may proceed to alkenes that are constitutional isomers with one formed in excess of the other.
In many cases elimination reactions may proceed to alkenes that are isomeric but with one formed in excess of the other.
www.mhhe.com /physsci/chemistry/carey/student/olc/graphics/carey04oc/ref/ch05eliminationreactions.html   (1763 words)

 Elimination of 2-Methylcyclohexanol   (Site not responding. Last check: 2007-10-21)
Elimination, as well as substitution reactions are very important in organic chemistry.
An equilibrium is established between reactants and products and therefore, to drive the reaction forwards the products are removed; in our case through distillation, since the boiling points of the products are much lower than of the reactant.
The elimination of 2-methylcyclohexanol was performed with an effective yield of 64.6%.
www.chemistry.emory.edu /mccormick/reports/elimination.htm   (1611 words)

 E2 Elimination Reaction
This reaction illustrates the base-induced dehydrohalogenation of alkyl halides with strong base and is used extensively for the preparation of alkenes.
Elimination reactions almost always yield an isomeric mixture of alkenes, where this is possible.
Under the reaction conditions, the elimination is regioselective and follows the Zaitsev rule when more than one route is available for the elimination of HX from an unsymmetrical alkyl halide.
www.owlnet.rice.edu /~chem215/ER/index.html   (1207 words)

 Explaining the elimination reaction producing propene from 2-bromopropane
Elimination involving more complicated halogenoalkanes and the competition between elimination and substitution in these reactions are dealt with on separate pages.
In an elimination reaction, the hydroxide ion hits one of the hydrogen atoms in the CH group and pulls it off.
The E stands for elimination, and the 2 is because the initial slow part of the reaction involves 2 species.
www.chemguide.co.uk /mechanisms/elim/elimtt.html   (401 words)

 esm_bruice_organic_4|Elimination Reactions of Alkyl Halides;|Introduction   (Site not responding. Last check: 2007-10-21)
In an elimination reaction, the electronegative atom is removed along with a hydrogen from an adjacent carbon.
In an elimination reaction, two sigma bonds are broken and are replaced by a pi bond.
In the first edition of this book, the substitution and elimination reactions of alkyl halides were covered in a single chapter.
wps.prenhall.com /esm_bruice_organic_4/0,7842,742550-,00.html   (183 words)

 Elimination Diet -- Recommendations and Resources   (Site not responding. Last check: 2007-10-21)
For elimination in the context of chemistry see elimination reaction.'' Elimination is a residence hall game where every player is both the hunter and the hunted.
Gaussian elimination is, however, a good method for systems of equations over a field where computations are exact, such as finite fields.
Elimination communication (EC) is a process where a caregiver uses timing, signals, and cues to help an infant address his or her elimination needs.
www.becomingapediatrician.com /health/46/elimination-diet.html   (1150 words)

 SparkNotes: Review of Organic Chemistry IV: Terms
The reaction is so named because it is bimolecular (2 molecules) and because it involves the Elimination of a β-hydrogen.
The overall order of a reaction is the sum of "a" and "b" and tells how many molecules of reactant are involved in the transition state of the rate-limiting step.
Reaction intermediate - An intermediary molecule that accumulates in negligible quantities during a reaction.
www.sparknotes.com /chemistry/organic4/review/terms.html   (639 words)

 Alkyl Halide Reactivity
E2 elimination reactions of certain isomeric cycloalkyl halides show unusual rates and regioselectivity that are not explained by the principles thus far discussed.
The most sensible interpretation of the elimination reactions of 2- and 4-substituted halocyclohexanes is that this reaction prefers an anti orientation of the halogen and the beta-hydrogen which is attacked by the base.
Having discussed the many factors that influence nucleophilic substitution and elimination reactions of alkyl halides, we must now consider the practical problem of predicting the most likely outcome when a given alkyl halide is reacted with a given nucleophile.
www.cem.msu.edu /~reusch/VirtualText/alhalrx3.htm   (2621 words)

 [No title]
The above reaction is commonly known as the beta elimination because one of the leaving group (X2) is lost from the a carbon and the other (X1) from the adjacent b carbon.
The E1 (elimination, monomolecular) is a two-step process in which the rate limiting step is the ionization of the organic chemical to produce a carbo cation which rapidly loses a b proton to a base, usually the solvent.
The E2 mechanism (elimination, bimolecular) is a one-step process in which two leaving groups depart simultaneously with the proton being pulled off by a base.
web.umr.edu /~kapilas/other_substitutions.html   (1129 words)

 [No title]   (Site not responding. Last check: 2007-10-21)
In the E2 elimination reaction, the carbon-hydrogen sigma bond and the carbon-leaving group sigma bond must lie in the same plane.
Syn elimination is much less common but does occur when the leaving group and the hydrogen are held syn-coplanar in an eclipsed, or nearly eclipsed, conformation of a rigid compound.
In cyclohexane derivatives, anti elimination requires that the hydrogen and the leaving group be trans and in the conformation where they are both axial (trans-diaxial elimination).
www.du.edu /~jhornbac/organic/e2synant.html   (248 words)

The rate of an E2 reaction is directly proportional to the concentartion of the substrate as well as that of the base used.
It is readily apparent that the reaction must be bimolecular and at the transition state of the RDS must involve bot the substrate as well as the base.
Elimination reactions carried out on cyclic molecules lend support for the anti-perplanar requirement in E2 reactions.
www.wiu.edu /users/mftkv/CHEM330(00)/elimination.html   (1114 words)

 VRML E2 Elimination Reaction   (Site not responding. Last check: 2007-10-21)
The VRML scene below is a demonstration of the E2 elimination reaction between hydroxide ion and 1-bromo-2-methylpropane.
This reaction procedes in a stereospecific manner - the hydrogen that is removed must be anti to the bromine.
The reaction is dependent on conformation - the hydrogen must be anti to the leaving group or no reaction occurs.
www.sienahts.edu /~swathen/vrml/e2-rxn.html   (162 words)

 E2 - Elimination   (Site not responding. Last check: 2007-10-21)
The E2 elimination reaction is a concerted reaction that results in the formation of a pi-bond: either an alkene or an alkyne.
In order for an E2 reaction to occur, there must be a strong base present to initiate the reaction by removing the hydrogen.
Like the SN2 reaction, the E2 reaction has a very specific geometry - the hydrogen that is removed, and the leaving group must be anti to one another.
www.sienahts.edu /~swathen/organic/e2.html   (179 words)

 Alkenes - Elimination
The reactions which do this are called elimination reactions, because two atoms or groups are "eliminated" from an alkyl halide or alcohol so that the double bond can be formed.
In elimination reactions the major product is the one in which the maximum number of substituents is attached to the doubly bonded carbons.
Since the rate of reactions proceeding by this mechanism is determined by the rate at which the carbocation is formed, the effect of changing alkyl group structure is the same as it was for the S
chemistry2.csudh.edu /rpendarvis/AlkeneElim.html   (1675 words)

 Organic Reactions
The equilibrium constant for this reaction is sensitive to the substituents on the C=O double bond.
In either case, the reaction is carried by a reagent that donates a pair of electrons to a carbon atom to form a new covalent bond.
In the course of this reaction, one nucleophile (the OH ion) is substituted for another (the Br ion).
chemed.chem.purdue.edu /genchem/topicreview/bp/3organic/organic.html   (3490 words)

 L19. Thermodynamic Properties, Reaction Pathways, Kinetics and Chemical Activation Analysis for Addition Reactions of H ...
One important class of reactions for aromatic compounds is addition to the aromatic ring by radical species and the subsequent reaction or isomerization of the corresponding cyclohexadienyl adduct, which is formed.
The reactions are of importance in combustion chemistry and the reaction with OH is of major importance in atmospheric chemistry The reaction paths, products and kinetics of these radical reactions are important to understanding and modeling the oxidation chemistry of these and many other (related) aromatic species.
elementary reaction path and the flux through each channel as a function of temperature and pressure Kinetic analysis is performed using bimolecular chemical activation methodology and an elementary reaction mechanism is constructed to evaluate overall rate constants to the varied reaction paths.
www.cstl.nist.gov /div838/kinetics2001/agenda/l_session/l19/l19.htm   (367 words)

 [No title]
Most elimination reactions fall somewhere in between the extreme points on this continuum of possibilities.
In either case, elimination reactions start with some substituted hydrocarbon of the general formula shown in Figure 2.
You will perform the reaction in a distillation apparatus so that the alkene products can continuously distill out of the boiling pot as soon as they are formed.
www.naz.edu:9000 /~organic/spring/laboratory/spexp1.htm   (1114 words)

The elimination of water from 2-methyl-3-butyn-3-ol followed by the addition of dichlorocarbene to the elimination product affords an excellent reaction sequence for the application of spectroscopic methods for the analysis of organic reaction products.
For the elimination of water from 2-methyl-3-butyn-2-ol, the literature suggests a 30% sulfuric acid in water mixture.* Although we have found this mixture to work, the yield and the substantial amounts of residue after the first distillation do leave considerable room for improvement.
The inclusion of the elimination reaction has substantial educational value and is a considerably less expensive source of 2-methyl-1-buten-3-yne.
virtual.yosemite.cc.ca.us /smurov/carbene.htm   (1031 words)

 elimination v nucleophilic substitution in halogenoalkanes
In all simple elimination reactions the things being removed are on adjacent carbon atoms, and a double bond is set up between those carbons.
In the substitution reaction between a halogenoalkane and OH ions, the hydroxide ions are acting as nucleophiles.
Important: If the elimination mechanism is on your syllabus, you are quite likely to be asked questions in which the substitution reaction crops up as well.
www.chemguide.co.uk /mechanisms/elim/elimvsubst.html   (633 words)

 Chapter 9   (Site not responding. Last check: 2007-10-21)
In this addition reaction, the carbonyl (C=O) compound reacts with "methyl lithium", (CH LI), an unstable, air and water sensitive reagent, initially to form the lithium salt of an alcohol.
The following is an elimination reaction and not an oxidation or reduction.
The same concentration of acid is present at the end of the reaction as at the beginning, although individual hydrogen atoms may have changed.
www.chem.unl.edu /cak/book9.htm   (1080 words)

 Characteristics of E2 Mechanism
In the following reactions, it is possible for an H to be anti to give each of the products without difficulty.
Elimination reactions are often not strictly E1 or E2.
The E1cB mechanism occurs when L is a poor leaving group and the structure of the substrate has an acidic H. It will be acidic because certain structural features are present that stabilize the conjugate base anion.
www.ipfw.edu /chem/261/261Fall03/261nt02p.htm   (685 words)

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