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In the News (Sat 25 May 19)

  
 PlanetMath: proof of rearrangement inequality
This is version 1 of proof of rearrangement inequality, born on 2002-11-10.
"proof of rearrangement inequality" is owned by pbruin.
We first prove the rearrangement inequality for the case
planetmath.org /encyclopedia/ProofOfRearrangementInequality.html

  
 Cope rearrangement - Wikipedia, the free encyclopedia
The Cope rearrangement is an extensively studied organic reaction involving the [3,3]-sigmatropic rearrangement of 1,5-dienes.
Although the Cope rearrangement is concerted, it is considered to go via a transition state that is energetically and structurally equivalent to a diradical.
The Cope rearrangement causes the fluxional states of the molecules in the bullvalene family.
en.wikipedia.org /wiki/Cope_rearrangement

  
 Chemical reaction - Wikipedia, the free encyclopedia
Reaction rates are related to the concentrations of substances involved in reactions, as quantified by the law of mass action.
The enthalpy of a reaction is calculated using standard reaction enthalpies and Hess' law of constant heat summation.
Nuclear reactions are not considered chemical reactions, although chemical reactions may follow a nuclear transformation.
en.wikipedia.org /wiki/Chemical_reaction

  
 Rearrangement
Rearrangement to a 2º-carbocation is favored by relief of small-ring strain in the case of pinene, and relief of steric congestion in the case of camphene.
Rearrangements consisting of consecutive 1,2-shifts often take place in a concerted, and therefore stereospecific fashion; however, it must not be assumed that the group shifts are simultaneous.
The rearrangement of acyl nitrenes to isocyanates that is the crux of the Hofmann, Curtius and Lossen rearrangements, is paralleled by the rearrangement of acyl carbenes to ketenes, a transformation called the Wolff rearrangement.
www.cem.msu.edu /~reusch/VirtualText/rearrang.htm

  
 Beckmann rearrangement - Wikipedia, the free encyclopedia
In the rearrangement reaction the alkyl group attached to the carbon atom displaces the activated hydroxyl group and an intermediate iminium ion is formed.
The reaction mechanism for the Beckmann rearrangement is generally believed to consist of an alkyl migration over the carbon to nitrogen double bond with expulsion of the hydroxyl group to an iminium ion followed by hydrolysis.
In organic chemistry, the Beckmann rearrangement, named after the german chemist Ernst Beckmann, is an acid-catalyzed rearrangement reaction of an oxime to an amide.
en.wikipedia.org /wiki/Beckmann_rearrangement   (573 words)

  
 Claisen Rearrangement
All Claisen Rearrangement reactions described to date require temperatures of > 100 °C if uncatalyzed.
The aromatic Claisen Rearrangement is accompanied by a rearomatization:
The aliphatic Claisen Rearrangement is a [3,3]-sigmatropic rearrangement in which an allyl vinyl ether is converted thermally to an unsaturated carbonyl compound.
www.organic-chemistry.org /namedreactions/claisen-rearrangement.shtm   (183 words)

  
 Patent 5225547: Reaction accelerator for rearrangement of oxime to amide and process for producing amides by rearrangement of oximes
Rearrangement of an oxime to an amide is known as Beckmann rearrangement.
However, when these solid catalysts are used in rearrangement reactions, it is necessary to adopt gas phase reaction at high temperatures, so that the reaction is accompanied by a reduction of.epsilon.-caprolactam yield, a degradation of catalyst and an increase of energy cost.
When the reaction accelerator is a solid which is not dissolved in a solvent, the reaction is effected in the state that the reaction accelerator is suspended in the solvent or effected in a flow reactor in which the reaction accelerator is present in the form of a fixed layer.
www.freepatentsonline.com /5225547.html   (183 words)

  
 A. Burchard: "Cases of Equality ..." (Abstract)
The Riesz rearrangement inequality says that this functional is maximized (under certain "size" constraints) by triples of non-increasing radial functions.
KEY WORDS: convolution, spherical rearrangement, Steiner/Schwarz symmetrization, Brunn-Minkowski inequality, distribution function, triangle inequality, ellipsoid.
We determine the cases of equality in this inequality.
www.math.virginia.edu /~ab4v/abstracts/riesz.html   (183 words)

  
 Encyclopedia: Claisen rearrangement
The Eschenmoser-Claisen rearrangement proceeds from an allylic alcohol to a γ,δ-unsaturated amide, and was developed by Albert Eschenmoser in 1966.
The aromatic variation of the Claisen rearrangement is the [3,3]-sigmatropic rearrangement of an allyl phenyl ether to an intermediate which quickly tautomerizes to an ortho-substituted phenol.
The Ireland-Claisen rearrangement is the reaction of an allylic acetate with strong base (such as butyl lithium) to give a γ,δ-unsaturated carboxylic acid.
www.nationmaster.com /encyclopedia/Claisen-rearrangement   (183 words)

  
 Cope Rearrangemnt
We are examining the substituent effects on the orbital energy separation in the Cope intermediates in order to determine the nature of the CI coefficients in the two configuration wave function for both the chair and the boat pathways of the Cope rearrangement.
From this description, it is clear that an important consideration for the transition state of the Cope rearrangement is the relative energy of the b
One should not be mislead by the simple pictures drawn for the transition state of the Cope rearrangement.
www.chem.purdue.edu /wenthold/cope.htm   (183 words)

  
 Sigmatropic reaction - Wikipedia, the free encyclopedia
The most well known of the sigmatropic rearrangements are the (3,3) Cope rearrangement and Claisen rearrangement.
Sigmatropic rearragements are classified by the substituent which moves and the backbone number of the destination substituent, for example a (1, 5) hydride shift.
en.wikipedia.org /wiki/Sigmatropic_reaction   (183 words)

  
 Untitled Document
The reaction was predicted to take about 61 hours, mainly for the heating of the allylic alcohols in preparing them to undergo the Claisen rearrangement.
This Claisen rearrangement produces a high level of one stereoisomer, but some of the product does not appear to be the desired conformation because of the nonbonding interactions between ethoxy and specific alkene substitiuents.
The most productive method found to accomplish this reaction was a Claisen rearrangement.
www.umich.edu /~chemh215/W04HTML/SSG4/ssg1/refs.htm   (183 words)

  
 Patent 4254291: Allylic rearrangement process
A process for allylic rearrangement, particularly terpenoid allylic rearrangement, utilizing certain acid forming metals to form an ester or alcoholate (alcohologen) of the allylic alcohol to be rearranged, isomerizing and cleaving the alcohologen in the presence of a transition metal compound catalyst and recovering the rearranged alcohol.
The instant invention relates to a process for enhancing allylic rearrangement beyond the equilibrium between an allylic primary or secondary alcohol and an allylic tertiary alcohol that is attainable in the liquid phase rearrangement of an allylic tertiary alcohol to an allylic primary or secondary alcohol at modest temperature (generally between 50.degree.
The process of claim 1 wherein said tertiary allylic alcohologen is formed in said reaction mixture by a collateral reaction that is concurrent with the isomerizing of said alcohologen.
www.freepatentsonline.com /4254291.html   (183 words)

  
 Beckmann rearrangement - Wikipedia, the free encyclopedia
In chemistry, the Beckmann rearrangement is an acid-catalyzed rearrangement of an oxime to an amide.
This example reaction starting with cyclohexanone to the caprolactam is the most important application of the Beckmann rearrangement.
The caprolactam is hydrolysed and then polymerized to Nylon.
www.wikipedia.org /wiki/Beckmann_rearrangement   (183 words)

  
 1,2-rearrangement - Wikipedia, the free encyclopedia
The 1,2-rearrangement belongs to a broad class of chemical reactions called rearrangement reactions.
The driving force for the actual migration of a substituent in step two of the rearrangement is the formation of a more stable intermediate.
For instance a tertairy carbocation is more stable than a secondary carbocation and therefore the SN1 reaction of neopentyl bromide with ethanol yields tert-pentyl ethyl ether.
en.wikipedia.org /wiki/1,2-rearrangement   (183 words)

  
 Journal of the Chemical Society C: Organic articles
No amino-Claisen rearrangement occurred in the reactions of propiolonitrile, chloropropiolonitrile, or (diethylamino) propiolonitrile with allylamine or diallylamine.The thio-Claisen rearrangement occurred in the reactions of chloropropiolonitrile and (diethylamino)propiolonitrile with prop-2-enethiol at room temperature.
Claisen, amino-Claisen, and thio-Claisen rearrangements in the reactions of cyano-acetylenes with allyl alcohol, prop-2-ynol, allyl amines, and prop-2-enethiol
The Claisen rearrangement was observed in the reaction of (diethylamino) propiolonitrile with allyl alcohol in the presence of boron trifluoride etherate at room temperature.
www.rsc.org /Publishing/Journals/J3/article.asp?doi=J39710000196   (105 words)

  
 LECTURE 4
Definition: The reactions in which the carbon skeleton of the molecule is rearranged to give a structural isomer of the original molecule are known as rearrangement reactions.
A classical example of Molecular Rearrangement reaction is shown by the five membered cyclic transition state of acetoxyl groups in solvolytic reaction of benzoyl ephedrine.
Thermal Rearrangements - Many reactions involving high temperature often go by formation of radicals and ions but rearrangement reactions have been carried out in the vapour phase, so it is unlikely that the reaction involves dissociation of the starting material into fragments such as radicals or ions.
www.uiowa.edu /intlinet/unijos/departments/pharmacology/rearrangment.htm   (105 words)

  
 TMPh A. V. Bogdanov, A. S. Gevorkyan, A. I. Denisenko, G. V. Dubrovskii - Quasi-classical analytical approximation of the $S$-matrix for the three-particle collinear rearrangement reaction
In the framework of the quasi-classical method of the Fock–Leontovich parabolic equation, the collinear problem of the three-particle rearrangement reaction is reduced to the quantum problem of a one-dimensional harmonic oscillator with a variable frequency in an external force field.
Bogdanov, A. Gevorkyan, A. Denisenko, G. Dubrovskii – Quasi-classical analytical approximation of the $S$-matrix for the three-particle collinear rearrangement reaction
Quasi-classical analytical approximation of the $S$-matrix for the three-particle collinear rearrangement reaction
math.ras.ru /tmph/scripts/tmph2.cgi?paperinfo=351   (105 words)

  
 Rearrangement
Rearrangement to a 2º-carbocation is favored by relief of small-ring strain in the case of pinene, and relief of steric congestion in the case of camphene.
The rearrangement of acyl nitrenes to isocyanates that is the crux of the Hofmann, Curtius and Lossen rearrangements, is paralleled by the rearrangement of acyl carbenes to ketenes, a transformation called the Wolff rearrangement.
Reactions # 6 & # 7 are interesting cases in which water is absent during the formation and reaction of the isocyanate.
www.cem.msu.edu /~reusch/VirtualText/rearrang.htm   (105 words)

  
 Rearrangement inequality - Wikipedia, the free encyclopedia
Many famous inequalities can be proved by the rearrangement inequality, such as the arithmetic mean - geometric mean inequality, the Cauchy-Schwartz inequality, and Chebyshev's sum inequality.
The rearrangement inequality can be proved by induction.
This page was last modified 04:38, 28 April 2005.
en.wikipedia.org /wiki/Rearrangement_inequality   (105 words)

  
 Substituent Effects on the Cope Rearrangement Neither Centaurs nor Chameleons can Characterize Them
The Cope rearrangement involves pairwise interchange of C-1 with C-3 and C-6 with C-4 in the pyrolysis of 1,5-dienes, fig 1.
Phenyl and cyano substituent effects on the activation free energy of thermoneutral Cope rearrangements of 1,5-dienes are analyzed in terms of the activation free energies for formation of the two non-concerted mechanistic alternatives, cyclohexane-1,4-diyl and two allylic radicals.
For thermoneutral Cope rearrangements, the equation reveals that the free energy of activation is a function of the harmonic mean of the free energy of activation to produce the two allyl radicals and that to produce the cyclohexane diyl, eq.
www.arkat-usa.org /ark/journal/2002/I04_Sunko/DS-317D/317.asp   (105 words)

  
 Nat' Academies Press, Biographical Memoirs V.73 (1998)
He convinced Bill that I should work on the mechanism of a different type of allylic rearrangement, which was of substantial theoretical interest during that period At about this time (1940) Professor Morgan died and Bill Young was the popular choice to succeed him as department chairman.
The allylic rearrangement of crotyl bromide and crotylmagnesium bromide.
Winstein and Young unraveled the mechanisms for the rearrangement reactions (often known as allylic rearrangements) and showed how pure 5 and 7 could be prepared.
www.nap.edu /books/0309060311/html/364.html   (105 words)

  
 REARRANGEMENT REACTION
Rearrangement to an Aromatic Nucleus - In many reactions, a group A migrates from a substituted hetero atom Z and becomes directly attached to an ortho or para position of an aromatic nucleus.
Thermal Rearrangements - Many reactions involving high temperature often go by formation of radicals and ions but rearrangement reactions have been carried out in the vapour phase, so it is unlikely that the reaction involves dissociation of the starting material into fragments such as radicals or ions.
The reactions in which the carbon skeleton of the molecule is rearranged to give a structural isomer of the original molecule are known as rearrangement reactions.
www.uiowa.edu /intlinet/unijos/departments/pharmacology/Afolabi/rearrangement_reaction.htm   (105 words)

  
 Beckmann
Johann Beckmann Johann Beckmann (1739-1811) was a German scientific author and coiner of the word technology and write a...
Beckmann was born in farming family, who gave up their farm and moved to Leip...
www.brainyencyclopedia.com /topics/beckmann.html   (105 words)

  
 Patent 4257950: Continuous preparation of .epsilon.-caprolactam by Beckmann rearrangement
267,114 discloses a process for the rearrangement of cyclohexanone-oxime, in which a cyclohexanone-oxime solution and sulfuric acid are passed simultaneously into a reaction vessel and the heat of reaction is removed by evaporation of the solvent.
The present invention relates to a process for the continuous preparation of.epsilon.-caprolactam by Beckmann rearrangement of cyclohexanone-oxime which is dissolved in a solvent which is inert towards oleum and immiscible with oleum and water, at an elevated temperature, with removal of the heat of rearrangement by evaporation of the solvent.
In the boiling zone 4, downstream of the mixing zone 3, the heat of rearrangement is removed by evaporation of the solvent, and the solvent which condenses in the condenser 5 is recycled.
www.freepatentsonline.com /4257950.html   (105 words)

  
 Hofmann rearrangement - Wikipedia, the free encyclopedia
The Hofmann rearrangement is an organic reaction in which a primary amide is converted to an amine upon treatment with bromine and a suitable base.
The amide reacts with the base and bromine to form an isocyanate intermediate, which then undergoes hydrolysis to form the corresponding amine.
The reaction is so named due to the intramolecular migration of the functional group to the adjacent nitrogen following its deprotonation.
en.wikipedia.org /wiki/Hofmann_rearrangement   (105 words)

  
 August Wilhelm von Hofmann
August Wilhelm von Hofmann (April 8, 1818 – May 5, 1892) was a German chemist.
The Hofmann rearrangement and Hofmann elimination reaction bear his namesake.
Hofmann's work covered a wide range of organic chemistry though with inorganic bodies he did but little.
www.1bx.com /en/August_Wilhelm_von_Hofmann.htm   (105 words)

  
 United States Patent Application: 0040053377
Rearrangement of the amide was performed when 0.16 g of (0.6 millimole) were dissolved in 0.4 mL of acetonitrile and added to 0.4 mL of an aqueous solution containing 0.4 g (0.9 millimole) of [bis(trifluoroacetoxy)iodo]benzene [(CF.sub.3CO.sub.2).sub.2PhI].
The method of claim 8, wherein the Curtius rearrangement is carried out by converting the carboxylic acid to the corresponding acyl chloride and then reacting the acyl chloride with an azide salt.
The rearrangement reactions that can be used in the practice of this invention include the Curtius rearrangement and modified versions of the Curtius rearrangement, the Lossen rearrangement and the Hoffmann rearrangement (FIG.
appft1.uspto.gov /netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PG01&p=1&u=/netahtml/PTO/srchnum.html&r=1&f=G&l=50&s1="20040053377".PGNR.&OS=DN/20040053377&RS=DN/20040053377   (11159 words)

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