The Fernandez reaction is reaction that occurs to signal a positive result in the lepromin skin test for leprosy . The reaction occurs in the skin at the site of injection if the body possesses antibody antibodies to the Dharmendra antigen , one of the antigen s found in Mycobacterium leprae , the bacteria that causes leprosy. The reaction occurs via a delayed type hypersensitivity mechanism. This reaction occurs within 48 hours of injection of lepromin and is seen in both lepromatous and tuberculoid forms of leprosy. In contrast, the Mitsuda reaction occurs 5 6 weeks after injection of lepromin and is only seen in patients with the tuberculoid form of leprosy not the lepromatous form, in which the body does not mount a strong response against the bacterium . In terms of mechanism of action and appearance, the reaction is similar to the tuberculin reaction of a positive Mantoux test for tuberculosis . Category Skin tests Category Leprosy medical stub ... more details
The Povarov reaction is an organic reaction described as a formal cycloaddition between an aromatic imine and an alkene . The imine in this organic reaction is a condensation reaction product from an aniline ... be able to donate electrons. Such alkenes are enol ether s and enamine s. The reaction product in the original Povarov reaction is a quinoline . Because the reactions can be carried out with the three components premixed in one reactor it is an example of a multi component reaction . Image Povarov reaction general.svg Povarov reactionReaction mechanism The reaction mechanism for the Povarov reaction ... base in a condensation reaction . The Povarov reaction requires a lewis acid such as boron trifluoride to activate the imine for an electrophilic addition of the activated alkene . This reaction ... substitution . Two additional elimination reaction s create the quinoline ring structure. Image PovarovReaction.gif frame center Scheme 1 . The Povarov reaction The reaction is also classified as a subset of aza Diels Alder reaction s ref Recent synthetic developments in a powerful imino Diels Alder reaction Povarov reaction application to the synthesis of N polyheterocycles and related alkaloids ... ref Examples The reaction depicted in scheme 2 illustrates the Povarov reaction with an imine ... in Povarov reaction of benzylidene 3 nitrophenyl amine Paul J. Stevenson and Isla Graham ... ref . This reaction is regioselective because the iminium ion preverentially attacks the nitro ..., the most electron rich ring position is now ortho and not para. The reaction is also Diastereomer ... 2 regio and diastereoselective Povarov reaction Variations One variation of the Povarov reaction is a four component reaction ref Straightforward Access to a Structurally Diverse Set of Oxacyclic Scaffolds through a Four Component Reaction Oscar Jim nez, Guillermo de la Rosa, Rodolfo Lavilla Angewandte ... cgi bin abstract 112092897 ABSTRACT Abstract ref . Whereas in the traditional Povarov reaction ... more details
The Doebner reaction is the chemical reaction of an aniline with an aldehyde and pyruvic acid to form quinoline 4 carboxylic acid s. ref Doebner, O. Ann. 1887 , 242 & 265. ref ref Bergstrom, F. W. Chem. Rev. 1944 , 35 , 156. Review ref Image Doebner Reaction Scheme.png center 350px The Doebner reaction References Reflist See also Conrad Limpach reaction Doebner Miller reactionreaction stub Category Carbon carbon bond forming reactions Category Condensation reactions Category Quinoline forming reactions Category Multiple component reactions Category Name reactions ar ca Reacci de Doebner es S ntesis de quinolinas de Doebner zh ... more details
A stepwise reaction ref http www.iupac.org goldbook S05970.pdf IUPAC Gold Book definition ref is a chemical reaction with one or more reaction intermediate s and involving at least two consecutive elementary reaction s. The rate law of an elementary reaction is rather simple. On the other hand, when combining multiple elementary steps, the rate law can become rather complex. Moreover, when speaking about catalytic reactions, the diffusion may also limit the reaction. In general, however, there is one very slow step, which is the rate determining step, i.e. the reaction doesn t proceed any faster than the rate determining step proceeds. Organic reactions, especially when involving catalysis , are often stepwise. For example, a typical enol reaction consists of at least these elementary steps Deprotonation next to to the carbonyl HC&ndash C O C C&ndash O sup &ndash sup Attack of enolate R sup sup C C&ndash O sup &ndash sup R&ndash C&ndash C O R sup sup is an electron acceptor, for example, the carbon of a carbonyl C O . A very strong base, usually an alkoxide , is needed for the first step. Reaction intermediates may be trapped in a trapping reaction . This proves the stepwise nature of the reaction and the structure of the intermediate. For example, superacid s were used to prove the existence of carbocation s. See also Lindemann mechanism External links references Category Chemical kinetics reaction stub et Astmeline reaktsioon pt Rea o em etapas ... more details
Notability date March 2010 Reaction is a Perl application framework built upon Catalyst software Catalyst , using Moose Perl Moose , DBIx Class and Template Toolkit . It is inspired by Apache Wicket . External links http search.cpan.org perldoc?Reaction Manual Reaction documentation Compu prog stub Category Perl software Category Web application frameworks ... more details
The Bunsen Reaction is a chemical reaction that describes water, sulfur dioxide , and iodine reacting to form sulfuric acid and hydrogen iodide . This reaction is the first step in the Sulfur iodine cycle to produce hydrogen . 2H sub 2 sub O SO sub 2 sub I sub 2 sub H sub 2 sub SO sub 4 sub 2HI The reaction is named after Robert Bunsen . A similar reaction is the basis for Karl Fischer titration . unreferenced date October 2007 Category Inorganic reactions reaction stub nl Bunsen reactie ... more details
The Pellizzari reaction is the chemical reaction of an amide and a hydrazide to form a 1,2,4 triazole . ref Pellizzari, G. Gazz. Chim. Ital. 1911 , 41 , 20. ref Image Pellizzari Reaction Scheme.png center 400px The Pellizzari reaction References Reflist See also Einhorn Brunner reactionreaction stub Category Condensation reactions Category Heterocycle forming reactions Category Name reactions es Reacci n de Pellizzari id Reaksi Pellizzari nl Pellizzari reactie ja zh ... more details
The Kochi reaction is an organic reaction for the decarboxylation of carboxylic acid s to alkyl halide s with lead tetraacetate and a lithium chloride or other lithium salts ref A New Method for Halodecarboxylation of Acids Using Lead IV Acetate Jay K. Kochi J. Am. Chem. Soc. 1965 87 11 2500 2502. DOI 10.1021 ja01089a041 ref . Image Kochi reaction.png The Kochi reaction 550px The reaction is a variation of the Hunsdiecker reaction . References Reflist DEFAULTSORT Kochi Reaction Category Organic reactions Category Name reactions de Kochi Reaktion pl Reakcja Kochiego zh Kochi ... more details
In chemistry , a concerted reaction is a chemical reaction in which all bond breaking and bond making occurs in a single step. Reactive intermediate s or other unstable high energy intermediates are not involved. Concerted reaction rate s tend not to depend on solvent Chemical polarity polarity ruling out large buildup of electrical charge charge in the transition state . Pericyclic reactions are concerted reactions. In the SN2 S sub N sub 2 reaction a concerted reaction also takes place. Because the reaction rate is bimolecular there are two molecular species controlling the rate of the reaction. Because the rate is dependent on two molecules the reaction does not have any intermediate steps, only a transition state . This means that all the bond making and bond breaking takes place in a single step. In order for the reaction to occur both molecules must be situated correctly. Therefore, the reaction is said to be concerted because it occurs in one step. References Carey, Francis A. Sundberg, Richard J. 1984 . Advanced Organic Chemistry Part A Structure and Mechanisms 2nd ed. . New York N.Y. Plenum Press. ISBN 0 306 41198 9. Category organic reactions ar es Reacci n concertada fr R action concert e nl Concerted reactie pl Reakcja skoordynowana pt Rea o concertada zh ... more details
The Thorpe reaction is a chemical reaction described as a self condensation of aliphatic nitrile s catalyzed by Base chemistry base to form enamine s. Ref Baron1904 Ref Ziegler1933 Ref Schaefer1967 The reaction was discovered by Jocelyn Field Thorpe . Image Thorpe Reaction Scheme.png center 500px The Thorpe reaction Thorpe Ziegler reaction The Thorpe Ziegler reaction named after Jocelyn Field Thorpe and Karl Ziegler , or Ziegler method , is the intramolecular modification with a dinitrile as a reactant and a cyclic ketone as the final reaction product after acidic hydrolysis. The reaction is conceptually related to the Dieckmann condensation . External links Thorpe Ziegler reaction 4 Phosphorinanone, 1 phenyl Organic Syntheses , Coll. Vol. 6, p.932 1988 Vol. 53, p.98 1973 http www.orgsynth.org orgsyn pdfs CV6P0932.pdf Link References Note Baron1904 Baron, H. Remfry, F. G. P. Thorpe, Y. F. J. Chem. Soc. 1904 , 85 , 1726. Note Ziegler1933 Karl Ziegler et al. Ann. 1933 , 504 , 94. Note Schaefer1967 Schaefer, J. P. Bloomfield, J. J. Org. React. 1967 , 15 , 1. Review Category Carbon carbon bond forming reactions Category Condensation reactions Category Name reactions de Thorpe Ziegler Reaktion ja ru zh es Reacci n de Thorpe ... more details
In chemistry , a reaction mechanism is the step by step sequence of elementary reaction s by which overall ... observable for most chemical reaction s, experiment s can often be designed that suggest the possible sequence of steps in a reaction mechanism. Recently, electrospray ionization mass spectrometry ... ref has been used to corroborate the mechanism of several organic reaction proposals. Description ... chemical reaction transformation . It also describes each reactive intermediate , activated complex ... the relative rates of the steps are. Reaction intermediates are chemical species, often unstable and short lived, which are not reactants or products of the overall chemical reaction, but are temporary products and reactants in the mechanism s reaction steps. Reaction intermediates are often free ... small.png thumb center 540px SN2 reaction S sub N sub 2 reaction mechanism. Note the negatively ... a reaction mechanism for example, see the illustration of the mechanism for benzoin condensation in the following examples section. A reaction mechanism must also account for the order in which molecules react. Often what appears to be a single step conversion is in fact a multistep reaction. Examples Consider the following reaction CO NO sub 2 sub &rarr CO sub 2 sub NO In this case, it has been experimentally determined that this reaction takes place according to the rate law math r k NO 2 2 math . Therefore, a possible mechanism by which this reaction takes place is 2 NO sub 2 sub &rarr ... reaction. When determining the overall rate law for a reaction, the slowest step is the step that determines the reaction rate. Because the first step in the above reaction is the slowest ..., it is a bimolecular reaction with a rate law of math r k NO 2 2 math . If we were to cancel out all the molecules that appear on both sides of the reaction, we would be left with the original reaction. In organic chemistry , one of the first reaction mechanisms proposed was that for the benzoin ... more details
The Betti reaction is a chemical reaction of aldehyde s, primary aromatic amine s and phenol s producing aminobenzylphenols. The Betti reaction is a special case of the Mannich reaction . Image Betti Reaction Scheme.png center 300px The Betti reaction References Betti, M. Gazz. Chim. Ital. 1900 , 30 II , 301. Betti, M. Gazz. Chim. Ital. 1903 , 33 II , 2. Organic Syntheses , Coll. Vol. 1, p.381 1941 Vol. 9, p.60 1929 . http www.orgsyn.org orgsyn prep.asp?prep cv1p0381 Article Pirrone, F Gazz. Chim. Ital. 1936 , 66 , 518. Pirrone, F Gazz. Chim. Ital. 1937 , 67 , 529. Phillips, J. P. Chem. Rev. 1956 , 56 , 286. Phillips, J. P. Barrall, E. M. J. Org. Chem. 1956 , 21 , 692. Category Addition reactions Category Multiple component reactions reaction stub Category Name reactions es Reacci n de Betti nl Betti reactie ja zh Betti ... more details
The Perkow reaction is an organic reaction in which a trialkyl phosphite ester reacts with a haloketone to form a dialkyl vinyl phosphate and an alkyl halide . Ref Perkow Image Perkow reaction.png center 500px The Perkow reaction In the related Michaelis Arbuzov reaction the same reactants are known to form a beta keto phosphonate which is an important reagent in the Horner Wadsworth Emmons reaction on the road to alkene s. The Perkow reaction, in this respect is considered a side reaction. Reaction mechanism The reaction mechanism of the Perkow reaction consists of a nucleophilic displacement of the halogen atom by the phosphorus nucleophile . The phosphite ester salt is subject to keto enol tautomerism and if the enol isomer is predominant the Perkow adduct is formed otherwise the keto form results in the Michaelis Arbuzov adduct. The second step of the reaction is a second nucleophilic displacement of the halide anion on one of the phosphite alkoxide substituent s forming an enol phosphonium oxide . Image Perkow mechanism.png center 550px Perkow reaction mechanism. The Arbusov product is shown in gray Scope The Perkow reaction has been applied in the synthesis of a novel insect repellent Ref Baldur based on hexachloroacetone and triethylphosphite which is able to engage in a secondary .... The authors report mediocre yields. Image Perkow reaction hexachloroacetone 2.png center 800px Perkow reaction hexachloroacetone triethylphosphine adduct The Perkow reaction is also used in the synthesis of novel quinoline s. Ref Paleta When the substituent is butyl n butyl the reaction product is the classical Perkow adduct. In this reaction the leaving group is an electron deficient ... is phenyl not shown the phospite has a preference for reaction with the acyl group leading to an ethyl ... enol phosphates formed in good yields ca. 90 in the Perkow reaction can be used as phosphorylation ... of the Perkow Reaction Halocarboxylate Anions as Leaving Groups in 3 Acyloxyquinoline 2,4 1H,3H dione ... more details
The Ullmann reaction or Ullmann coupling ref cite journal title The Ullmann Synthesis of Biaryls author P.E. Fanta journal Synthesis volume 1974 issue pages 9 21 year 1974 url doi 10.1055 s 1974 23219 ref is a coupling reaction between aryl halide s with copper . The reaction is named after Fritz Ullmann . ref cite journal title Ueber Synthesen in der Biphenylreihe author F. Ullmann, Jean Bielecki ... reaction, note the unusual reaction medium, which, at these temperatures , is ordinary sand The traditional version of the Ullmann reaction requires harsh reaction conditions, and the reaction ... of the Ullmann Reaction author J. Hassan, M. Sevignon, C. Gozzi, E. Schulz, M. Lemaire journal Chemical ... ref The reaction mechanism of the Ullmann reaction is extensively studied. Electron spin resonance .... The reaction probably involves the formation of an organocopper compound RCuX which reacts with the other ... bond bond Metathesis reaction metathesis ref Derek van Allen, PhD Thesis, University of Massachusetts ... ref . The classical Ullmann reaction is limited to electron deficient aryl halides and requires harsh reaction conditions. Modern variants of the Ullman reaction employing palladium and nickel have widened the substrate scope of the reaction and rendered reaction conditions more mild. Yields are generally ... 0471264180.or063.03 ref In organic synthesis this reaction is often replaced by palladium coupling reactions such as the Heck reaction , the Hiyama coupling and the Sonogashira coupling . In a variation of the Ullmann reaction, 2 bromo vinyl benzene is reacted with imidazole in an ionic liquid ... promoted Ullmann type reaction of vinyl bromides with imidazoles in ionic liquids , Chemical Communications ... ref The reaction requires L proline L proline catalysis . Image UllmannReactionWang2005.svg center Imidazole Ullmann reaction. Note the reaction medium BMIMBF4 Note BMIMBF4 stands for the ionic liquid ... reagent used in the Ullmann reaction References Reflist DEFAULTSORT Ullmann Reaction Category Condensation ... more details
The Tishchenko reaction is a chemical reaction that involves disproportionation of an aldehyde lacking a hydrogen atom in the alpha position in the presence of an alkoxide . Ref 1 The reaction product is an ester . Catalyst s are aluminium alkoxides or sodium alkoxides. Benzaldehyde reacts with sodium benzyloxide generated from sodium and benzyl alcohol to benzyl benzoate . Ref 2 Image Tishchenko reaction.gif center The Tishchenko reaction benzaldehyde reacts to benzyl benzoate, the catalyst is generated in situ from sodium and benzyl alcohol formaldehyde Paraformaldehyde reacts with boric acid to methyl formate . Ref 3 The key step in the reaction mechanism for this reaction is a 1,3 hydride shift in the hemiacetal intermediate formed from two successive nucleophilic addition reactions, the first one from the catalyst. The hydride shift regenerates the alkoxide catalyst. Image Tishchenko reaction mechanism.gif center The Tishchenko reactionreaction mechanism In the related Cannizzaro reaction the base is sodium hydroxide and then the organic oxidation oxidation product is a carboxylic acid and the organic reduction reduction product is an alcohol . Related reactions Aldol Tishchenko reaction Baylis Hillman reaction Cannizzaro reaction Meerwein Ponndorf Verley Reduction Oppenauer Oxidation References Note 1 V. Tishchenko, J. Russ. Phys. Chem. Soc. 1906 , 38 , 355, 482, 540, 547. Note 2 OrgSynth author Kamm, O. Kamm, W. F. title Benzyl benzoate collvol 1 collvolpages 104 year 1941 prep cv1p0104 Note 3 cite journal author Paul R. Stapp journal J. Org. Chem. year 1973 volume 38 issue 7 pages 1433 1434 doi 10.1021 jo00947a049 title Boric acid catalyzed Tishchenko reactions Category Organic reactions Category Name reactions de Claisen Ti enko Reaktion ja zh es Reacci n ald lica de Tishchenko ... more details
Unreferenced stub auto yes date December 2009 Reaction shot is a term used in motion picture film production production and cinematography referring to a basic unit of film grammar. It is a shot which cuts away from the main scene in order to show the reaction of a character to it. A reaction shot usually implies the display of some sort of emotion on the face of the actor being shown, and is thus most commonly a close up shot although a group of actors may be shown reacting together . A reaction shot is also generally bereft of dialogue , though this is not an absolute rule. Its main purpose is to show an emotional response to the immediately preceding action or words of another character in the scene, or to an event in the immediately preceding scene which may or may not involve another actor e.g., an explosion, monster, empty room, etc. The assumption behind the logic of the reaction shot is that the emotional reaction of the actor being depicted will either advance the story, reveal character traits of the character in the reaction shot, or emphasize character traits of another character that were displayed in the action or dialog present in the preceding shot. A completely unemotional reaction may also be important if it provides information to the audience or is unexpected in the context of the scene. Reaction shots can be especially critical in comedy , as the reaction of an actor or actors to a dramatic incident provides a psychological cue to the audience about how to respond to that incident themselves. In some cases, the deliberate avoidance of showing a reaction shot can be used by a filmmaker to dramatic effect for instance, if the filmmaker wishes to conceal a character s motivations by hiding their reaction to a particular event. DEFAULTSORT Reaction Shot Category Film techniques Film term stub ... more details
merge from Wharton olefin synthesis discuss Talk Wharton reaction Merger candidate date September 2011 The Wharton reaction is the chemical reaction of , epoxide epoxy ketone s with hydrazine to give allylic alcohol s. Ref Wharton1961A Ref Wharton1961B Ref Chamberlin1991 It can be used to synthesize carenol compounds. Image Wharton Reaction Scheme.png center 350px The Wharton reaction Dupuy has developed an improved procedure. Ref Dupuy1989 Reaction mechanism The Reaction mechanism mechanism of the Wharton reaction begins with reaction of the ketone 1 with hydrazine to form a hydrazone 2 . Rearrangement of the hydrazone gives intermediate 3 , which can decompose giving off nitrogen gas forming the desired product 4 . Stork et al. have investigated the mechanism of the final decomposition and found that it can proceed by an ionic mechanism or a radical mechanism depending on reaction temperature, solvent used, and structure of intermediate 3 . Ref Stork1977 Image Wharton Reaction Mechanism.png center 600px The mechanism of the Wharton reaction Notice that the alcohol retains the configuration of the starting epoxide. The reaction is named after Peter Stanley Wharton. References Note Wharton1961A Phillip Simon Wharton Wharton, P. S. Bohlen, D. H. J. Org. Chem. 1961 , 26 , 3615. Note Wharton1961B Wharton, P. S. J. Org. Chem. 1961 , 26 , 4781. Note Chamberlin1991 Chamberlin, A. R. Sall, D. J. Comp. Org. Syn. 1991 , 8 , 927 929. Review Note Dupuy1989 Dupuy, C. Luche, J. L. Tetrahedron journal Tetrahedron 1989 , 45 , 3437. Note Stork1977 Stork, G. A. et al. J. Am. Chem. Soc. 1977 , 99 , 7067. See also Eschenmoser fragmentation Grob fragmentation Wolff Kishner reduction Category Organic redox reactions Category Name reactions es Reacci n de Wharton zh ... more details
chem stub Reactionbox verifiedrevid Reference Type ring condensation NamedAfter W. Pfitzinger Section1 Reactionbox Conditions Solvent protic Reaction Reactionbox Reaction Reactant1 ketone or aldehyde Reactant2 isatin Reactant3 potassium hydroxide Product1 quinoline 4 carboxylic acid Sideproduct1 water The Pfitzinger reaction also known as the Pfitzinger Borsche reaction is the chemical reaction of isatin with base and a carbonyl compound to yield substituted quinoline 4 carboxylic acid s. ref Pfitzinger, W. J. Prakt. Chem. 1886 , 33 , 100. ref ref Pfitzinger, W. J. Prakt. Chem. 1888 , 38 , 582. ref Image Pfitzinger Reaction Scheme.png center 400px The Pfitzinger reaction Several reviews have been published. ref Manske, R. H. Chem. Rev. 1942 , 30 , 126. Review ref ref Bergstrom, F. W. Chem. Rev. 1944 , 35 , 152. Review ref ref Shvekhgeimer, M. G. A. Chemistry of Heterocyclic Compounds 2004 , 40 , 257 294. Review, DOI 10.1023 B COHC.0000028623.41308.e5 ref Reaction mechanism Image Pfitzinger Reaction Mechanism.png center 650px The mechanism of the Pfitzinger reaction The reaction of isatin with a base such as potassium hydroxide hydrolysis hydrolyses the amide bond to give the keto acid 2 . This intermediate can be isolated, but is typically not. A ketone or aldehyde will react with the aniline to give the imine 3 and the enamine 4 . The enamine will cyclize and dehydrate to give the desired quiniline 5 . Variations Halberkann variant Image Pfitzinger Halberkann Modification Scheme.png center 350px The Halberkann variant of the Pfitzinger reaction Reaction of N acyl isatins with base gives 2 Hydroxyl hydroxy quinoline 4 carboxylic acid s. ref Halberkann, J. Chemische Berichte Ber. 1921 , 54 , 3090. ref References Reflist See also Camps quinoline synthesis Friedl nder synthesis Niementowski quinazoline synthesis Category Carbon carbon bond forming reactions Category Condensation reactions Category Quinoline forming reactions Category Name reactions de Pfitzinger Reakti ... more details
The Pr vost reaction is chemical reaction in which an alkene is converted by iodine and the silver salt chemistry salt of benzoic acid to a Vicinal chemistry vicinal diol with anti addition anti stereochemistry. ref cite journal author Charles Pr vost journal Comptes rendus volume 196 pages 1129 year 1933 title Sur un complexe iodo argento benzo que et son application l oxydation des combinaisons thyl niques en glycols url http gallica.bnf.fr ark 12148 bpt6k3148d f1129.table ref ref Charles Pr vost C.A. 27, 3195 1933 ref ref Wilson, C. V. Org. React. 1950 , 9 , 350. Review ref The reaction was discovered by the French chemist Charles Pr vost 1899 1983 . Image Prevost Reaction Scheme.png center 500px The Pr vost reactionReaction mechanism The reaction between silver benzoate 1 and iodine is very fast and produces a very reactive iodinium benzoate intermediate 2 . The reaction of the iodinium salt 2 with an alkene gives another short lived iodinium salt 3 . Nucleophilic substitution SN2 reaction S sub N sub 2 by the benzoate salt gives the ester 4 . Another silver ion causes the anchimeric assistance neighboring group substitution of the benzoate ester to gives the oxonium ion oxonium salt 5 . A second SN2 reaction S sub N sub 2 substitution by the benzoate anion give the desired diester 6 . Image Prevost Reaction Mechanism.png center 600px The mechanism of the Pr vost reaction In the final step hydrolysis of the ester groups gives the anti diol. This outcome is the opposite of that of the related Woodward cis hydroxylation which gives syn addition . References Reflist See also Woodward cis hydroxylation DEFAULTSORT Prevost Reaction Category Organic redox reactions Category Substitution reactions Category Name reactions de Pr vost Hydroxylierung zh ... more details
An exergonic reaction is a chemical reaction where the change in the Gibbs free energy is negative, ref IUPAC Gold Book definition http www.iupac.org goldbook E02262.pdf search Exergonic 20reaction exergonic exoergic reaction ref indicating a spontaneous reaction . Symbolically, the release of Gibbs free energy, G , in an exergonic reaction is denoted as math Delta G G rm products G rm reactants 0. , math Although exergonic reactions are said to occur spontaneously , this does not imply that the reaction will take place at an observable Reaction rate rate . For instance, the Catalysis Background disproportionation of hydrogen peroxide is very slow in the absence of a suitable catalyst. It has been suggested that eager would be a more intuitive term in this context. ref cite journal doi 10.1021 ed061p710 last Hamori first Eugene coauthors James E. Muldrey year 1984 title Use of the world eager instead of spontaneous for the description of exergonic reactions journal Journal of Chemical Education volume 61 issue 8 pages 710 ref More generally, the terms exergonic and endergonic relate to the Gibbs free energy change in any process, not just chemical reactions. An example of an exergonic reaction is cellular respiration. The terms exothermic and endothermic reactions relate to the enthalpy change of a process. See also Endergonic reaction References reflist Category Thermochemistry de Exergon pl Reakcja egzoenergetyczna ... more details
The Del pine reaction is the organic synthesis of primary amine s 4 by reaction of a benzyl or alkyl halide s 1 with hexamethylenetetramine 2 followed by acid chemistry acid hydrolysis of the quaternary ammonium salt 3 . ref M. Del pine Bull.Soc.Chim.Fr. . 1895 , 13, S. 352 361 ref ref Alexander R. Surrey Name Reactions in Organic Chemistry . 2nd Edition, Academic Press, 1961 ref It is named after the French chemist St phane Marcel Del pine 1871 1965 . Image Delepine2.png 495px center Delepin reaction Advantages of this reaction are selective access to the primary amine without side reaction s from easily accessible reactants with short reaction times and relatively mild reaction conditions. An example is the synthesis of 2 bromoallylamine from 2,3 dibromopropene. ref OrgSynth title 2 Bromoallylamine author Albert T. Bottini, Vasu Dev, and Jane Klinck collvol 5 collvolpages 121 year 1973 prep cv5p0121 ref Reaction mechanism The benzyl halide or alkyl halide 1 reacts with hexamethylenetetramine to a quaternary ammonium salt 3 , each time just alkylating one nitrogen atom. By reflux ing in concentrated ethanolic hydrochloric acid solution this salt is converted to the primary amine together with formaldehyde as the acetal with ethanol and ammonium chloride . References references DEFAULTSORT Delepine Reaction Category Substitution reactions Category Name reactions de Del pine Reaktion ru zh ... more details
The Bosch reaction is a chemical reaction between carbon dioxide and hydrogen that produces elemental carbon graphite , water and a 10 return of invested heat . This reaction requires the introduction of iron as a catalyst and requires a temperature level of 530 730 degrees Celsius. ref Messerschmid, Ernst and Reinhold Bertrand. Space Stations. Springer. 1999. ref The overall reaction is as follows CO sub 2 sub gas g 2 H sub 2 sub g C solid s 2 H sub 2 sub O g The above reaction is actually the result of two reactions. The first reaction, the reverse water gas shift reaction , is a fast one. CO sub 2 sub H sub 2 sub CO H sub 2 sub O The second reaction controls the reaction rate . CO H sub 2 sub C H sub 2 sub O The overall reaction produces 2.3× 10 sup 3 sup joule s for every gram of carbon produced at 650 C. Reaction temperatures are in the range of 450 to 600 C. The reaction can be accelerated in the presence of an iron , cobalt or nickel catalyst . Ruthenium also serves to speed up the reaction. Together with the Sabatier reaction the Bosch reaction is studied as a way to remove carbon dioxide and to generate clean water aboard a space station ref http oregonstate.edu atwaterj h2o gen.htm Methods of water production ref The reaction is also used to produce graphite for radiocarbon dating with Accelerator Mass Spectrometry . It is named after the German chemist Carl Bosch . Citation needed date March 2008 The Bosch reaction is being investigated for use in maintaining space station life support. Though the Bosch reaction would present a completely closed hydrogen and oxygen cycle which only produces atomic carbon as waste, difficulties maintaining its higher required temperature and properly handling carbon deposits mean significantly more research will be required ... carbon tends to foul the catalyst s surface, which is detrimental to the reaction s efficiency ... A carbon dioxide reduction unit using Bosch reaction Category Organic redox reactions Category ... more details
Unreferenced date August 2010 In theoretical physics , Back reaction is often necessary to calculate the behavior of a Elementary particle particle or an object in an external field. When the particle is considered to be infinitely light or have an infinitesimal charge, it is said that we deal with a probe and the back reaction is neglected. However, a real object also carries a mass and charges itself. They modify the original environment for example, they help to curve the space in general relativity and this modification the back reaction has to be taken into account when a more accurate calculation is performed. In Cosmology the term Back reaction is used for the measure of the non commutativity of the averaging procedure and the dynamical evolution of space time. The existence of an isotropy scale is determined be the length scale at which the Back reaction parameter vanishes. The existence of such scale still needs experimental confirmation. Category Theoretical physics phys stub ... more details
Image EliminationReactionCyclohexene.svg frame right Elimination reaction of cyclohexanol to cyclohexene ... ref An elimination reaction is a type of organic reaction in which two substituent s are removed ... as the E2 reaction , and the two step mechanism is known as the E1 reaction . The numbers do not have to do with the number of steps in the mechanism, but rather the kinetics of the reaction, bimolecular ... the reverse of an addition reaction . When the substrate is asymmetric, regioselectivity is determined ... Kelk Ingold Sir Christopher Ingold proposed a model to explain a peculiar type of chemical reaction the E2 mechanism. E2 stands for bimolecular elimination. The fundamental elements of the reaction ... The reaction rate , influenced by both the alkyl halide and the base bimolecular , is second order reaction second order . Because E2 mechanism results in formation of a pi bond, the two leaving groups ... with higher energy. The reaction mechanism involving staggered conformation is more favorable ... effect is larger than 1. E2 is very similar to the SN2 reaction S sub N sub 2 reaction mechanism. Image E2 Elimination Reaction.png center 500px Scheme 1. E2 reaction mechanism An example of this type of reaction in scheme 1 is the reaction of isobutyl bromide with potassium alkoxide ethoxide in ethanol . The reaction products are isobutylene , ethanol and potassium bromide . E1 mechanism This section is linked from E1 E1 is a model to explain a particular type of chemical elimination reaction ... atom tertiary alkyl halides, but is possible with some secondary alkyl halides. The reaction rate ... step aka rate determining step . Therefore first order reaction first order kinetics apply unimolecular . Reaction usually occurs in complete absence of base or presence of only a weak base acidic conditions and high temperature . E1 reactions are in competition with SN1 reaction S sub N sub 1 reaction s because they share a common carbocationic intermediate. A deuterium isotope effect is absent ... more details
unreferenced date May 2009 In thermochemistry chemical thermodynamics , an endergonic reaction also called an unfavorable reaction or a nonspontaneous reaction is a chemical reaction in which the standard change in Thermodynamic free energy free energy is positive, and energy is absorbed. In layman s terms the total amount of energy is a loss it takes more energy to start the reaction than what you ... Exergonic reaction Exergonic Reaction . Under constant temperature and constant pressure conditions ... 0 math for the reaction at standard state i.e. at standard pressure 1 Bar unit bar , and standard concentrations ... constant for the reaction is related to G by the relation math K e frac Delta G circ RT math where ... math K 1 , math so that starting from molar stoichiometric quantities such a reaction would move ... in Free Energy process. Pull Reagents can be pulled through an endergonic reaction, if the reaction products are cleared rapidly by a subsequent exergonic reaction. The concentration of the products of the endergonic reaction thus always remains low, so the reaction can proceed. A classic example of this might be the first stage of a reaction which proceeds via a transition state . The process .... However, the reaction can proceed because having reached the transition state, it rapidly ... be pushed by coupling them to another reaction which is strongly exergonic, through a shared intermediate. This is often how biological reactions proceed. For example, on its own the reaction math X Y ... by coupling it to a strongly exergonic reaction such as, very often, the decomposition of Adenosine ... XY P i math This kind of reaction, with the ATP decomposition supplying the free energy needed to make an endergonic reaction occur, is so common in cell biochemistry that ATP is often called the universal energy currency of all living organisms. See also Endergonic Exergonic Exergonic reaction Exothermic Endothermic Exothermic reaction Endothermic reaction Warm blooded Endotherm Warm blooded ... more details
Encyclopedia
top
