Mechanism Of Racemization Research Articles

Mechanisms of Thermal Racemization of Sulfoxides1

Mechanisms of Thermal Racemization of Sulfoxides¹

Kinetic Studies of Solvolysis. XII. The Question of a Single Mechanism for the “Borderline” SN Reactions—The Solvolysis of Optically Active α-Phenylethyl Chloride in Aqueous Ethanol

Abstract Competitive solvolysis has been conducted in binary solvents of water and ethanol on optically active α-phenylethyl chloride at 40.0°C. The extents of inversion (α%) for solvolysis products, i. e., α-phenylethyl alcohol and α-phenylethyl ethyl ether, have been calculated from the optical rotations of these products isolated after ten half-lives, and the values of α% have been plotted Vs. the volume percentage of water. In the region of 90% aqueous ethanol, the two α% lines for the alcohol and the ether intersect with each other. This intersection of the two lines conflicts with any single mechanism for the borderline SN reactions, whereas the dual mechanism can explain this phenomenon without any difficulty. In the region of a 100% water-solvent (a typical medium for the SN1 solvolysis), the two lines do not converge to the same α% value. On the basis of these findings, a general mechanism of racemization for the SN1 solvolysis has also been discussed.

A Memory Effect in the Generation of 2-Bicyclo[3.2.1]octyl Cation. On the Mechanism of Racemization of 2-Bicyclo[2.2.2]octyl Cation1

A Memory Effect in the Generation of 2-Bicyclo[3.2.1]octyl Cation. On the Mechanism of Racemization of 2-Bicyclo[2.2.2]octyl Cation¹

A novel method for the determination of C-terminal amino acid in polypeptides by selective tritium labelling

Abstract In our previous communication ( Matsuo, 1965 ), we reported selective 2H- and 3H-labelling reaction at the C-terminal amino acid of several N-acetylpeptides through the C-terminal racemization mechanism. The selective deuteration or tritiation is based upon the C-terminal oxazolone formation in peptides by the action of acetic anhydride or dicyclohexylcarbodiimide, followed by the base-catalyzed hydrolytic ring-opening in deuterium oxide or tritium oxide as shown in the following scheme. The above selective C-terminal tritiation has now been applied to the determination of the known C-terminal amino acids of angiotensin II ( Skeggs, 1955 ) and beef-insulin ( Sanger, 1955 ). The experimental results described in this communication will indicate that the C-terminal determination of polypeptides or proteins may be accomplished in a simple manipulation and in a micro-scale by this method. A modification of the above procedure for identifying C-terminal aspartic acid and proline, which were two exceptions that resisted the oxazolone formation by the above method, will also be described.

Thermal racemization of some organometallic compounds containing elements of the first, second and third group of the periodic table and optically active alkyl groups

The chemical reactivity of organometallic compounds containing a tertiary carbon atom in the β position with respect to the metal atom, was studied by investigation of the thermal racemization of some organometallic compounds of Li, Mg, Be, Zn, Cd, B and Al containing optically active alkyl groups. At a temperature of 100° only the 2-methylbutyl derivatives of Be, B and Al racemize at an appreciable rate. When the asymmetric carbon atom is in the γ or δ position with respect to the metal atom, no racemization was observed. The influence of solvents on the optical activity decay rate and a reasonable mechanism of the thermal racemization of the investigated organometallic compounds are discussed.

Racemization studies on the bis(oxalato)2,2′-bipyridine-chromate (III) and the bis(oxalato)1,10-phenanthroline chromate (III) ions

Racemization studies on the new complex anions [Cr(ox)2bipy]- and [Cr(ox)2phen]-show a close similarity to each other in neutral, acidic and basic solutions. Comparisons with other Cr(III) oxalato complexes are made and possible racemization mechanisms are discussed.

The mechanism of racemisation during the coupling of acylpeptides

The mechanism of racemisation during the coupling of acylpeptides

715. Amino-acids and peptides. Part XIX. The mechanism of racemisation during peptide synthesis. “The chloride effect”

715. Amino-acids and peptides. Part XIX. The mechanism of racemisation during peptide synthesis. “The chloride effect”

The Mechanism of Racemization of the Hexadentate Complex of Cobalt(III) with Ethylenediaminetetraacetic Acid

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThe Mechanism of Racemization of the Hexadentate Complex of Cobalt(III) with Ethylenediaminetetraacetic AcidDean W. Cooke, Yong Ae Im, and Daryle H. BuschCite this: Inorg. Chem. 1962, 1, 1, 13–15Publication Date (Print):February 1, 1962Publication History Published online1 May 2002Published inissue 1 February 1962https://doi.org/10.1021/ic50001a004RIGHTS & PERMISSIONSArticle Views328Altmetric-Citations23LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (262 KB) Get e-Alerts Get e-Alerts

Complex Ions of Chromium. IX. Mechanism of Racemization and Isomerization, Reactions of Chelated Chromium(III) Ions1

Complex Ions of Chromium. IX. Mechanism of Racemization and Isomerization, Reactions of Chelated Chromium(III) Ions¹

On the Metabolism of Organic Acids by Clostridium acetobutylicum

The mechanism of racemization of optically active lactic acid by racemiase of Clostridium acetobutylicum was investigated. Pyruvic acid and enol-lactic acid were excluded from the possible intermediate of racemiase action. Among four radicals of lactic acid, that is methyl, hydrogen, hydroxyl and carboxyl radicals, hydroxyl radical was pointed out to be essential for the enzymatic reaction. Finally, acrylic acid (dehydrated form of lactic acid) was suggested as the intermediate. The role of coenzymic substances, both pyridoxamine phosphate and ferrous ion, was investigated using the non-ellzymatic racemization of lactic acid in the system including optically active lactic acid, pyridoxamine and ferrous sulphate. In this paper, it was proposed that a complex consisting of acrylic acid, pyridoxamine phosphate, ferrous ion and aporacemiase would be intermediary in racemiase reaction of this organism.

On the Metabolism of Organic Acids byClostridium acetobutylicum

Authors confirmatively observed the phenomena that in adequate conditions, the mode of acetone-butanol fermentation could be converted into homo-lactic acid fermentation, and that the formation of “Racemiase” (lactic acid racemiase) was intensified through the appropriate lactate level in growing culture of the bacterium, Clostridium acetobutylicum.Furthermore in this series of the papers, the possible role of “Racemiase” in the lactic acid metabolizing sequence was suggested, and the chemical properties of “Racemiase” as well as the mechanism of enzymatic racemization of lactic acid were investigated. The metabolism of several organic acids were also discussed in connection with the fermentation pathway of this organism.

Mechanism of Racemization of Complex Ions. IV. Effect of Added Large Ions upon the Rates of Dissociation and Racemization of Tris-(1,10-phenanthroline)-iron(II) Ion1,2

Mechanism of Racemization of Complex Ions. IV. Effect of Added Large Ions upon the Rates of Dissociation and Racemization of Tris-(1,10-phenanthroline)-iron(II) Ion^1,2

Additions and Corrections: Mechanism of Racemization of Complex Ions. III. Effect of Added Ions upon the Rates of Dissociation of Tris-(1,10-phenanthroline)-iron(II) and Tris(1,10- phenanthroline)-iron(III) and upon the Rate of Racemization of Tris-(1,10- phenanthroline)-iron(III).

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTAdditions and Corrections: Mechanism of Racemization of Complex Ions. III. Effect of Added Ions upon the Rates of Dissociation of Tris-(1,10-phenanthroline)-iron(II) and Tris(1,10- phenanthroline)-iron(III) and upon the Rate of Racemization of Tris-(1,10- phenanthroline)-iron(III).John Dickens, Fred Basolo, and H NeumannCite this: J. Am. Chem. Soc. 1957, 79, 24, 6579Publication Date (Print):December 1, 1957Publication History Published online19 May 2004Published inissue 1 December 1957https://doi.org/10.1021/ja01581a637RIGHTS & PERMISSIONSArticle Views58Altmetric-Citations-LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (157 KB) Get e-Alerts Get e-Alerts

Studies in Stereochemistry. XII. Mechanism of Racemization in Schiff Bases of D-Methionine Ethyl Ester.

Ethyl esters of N-isopropylidene-, N-benzylidene-, and N-p-nitrobenzylidene-D-methionine (II, I, and III) were prepared. The relative velocities of racemization of the Schiff bases were measured resulting in the order of (II)«(I)«(III). It has been postulated by Holland that prototropy in Schiff bases derived from α-amino acid esters occurs through tautomerism in the >C*H-N=C< structure. The relative velocities found experimentally were in reverse of the theoretical assumption that they would be (II) > (I) > (III) by the electronic effect of the N-substituent, if the said postulation were correct. The findings support the view that the prototropic change occurs originally in the >C*H-C=O structure and is additionally helped by the azomethine structure in the molecule.

Small-Ring Compounds. XIII. The Mechanism of Racemization of Optically Active 2,4-Dichloro-3-phenylcyclobutenone1

Racemization of optically active 2,4-dichloro-3-phenylcyclobutenone has been shown to involve reversible formation of (1-phenyl-2-chloroethenyl)-chloroketene 2,4-dichloro-3-phenyl-3-butenoic acid yields 2,4-dichloro-3-phenylcyclobutenone on treatment with acetic anhydride.

樟脳誘導体の合成研究 (第9報)

It was shown in the previous paper that α-trans-π-dihalo-d-camphor underwent peculiar isomerization by fuming sulfuric acid and formed 6-trans-π-dihalo-l-camphor. From the assumption of the racemization mechanism of camphor by sulfuric acid forwarded by Asahina, it was assumed that the above reaction passed through an intermediate of 5-trans-π-dihalo-d-camphor. Therefore, 5-bromo-trans-π-chloro-d-camphor was prepared from trans-π-chlorocamphor through trans-π-chloro-d-camphoquinone, trans-π-chlorodiazo-d-camphor, and trans-π-chloro-β-pericyclocamphanone. Application of fuming sulfuric acid to the 5-bromo derivative unexpectedly revealed that it is extremely stable to this acid and no change was found to occur. The same reaction of α-bromo-6-trans-π-dichloro-l-camphor showed that this substance is also stable to fuming sulfuric acid.

276. Isotopic exchange reactions of organic compounds. Part IV. The mechanism of racemisation of phenyl-p-tolylacetic acid

276. Isotopic exchange reactions of organic compounds. Part IV. The mechanism of racemisation of phenyl-p-tolylacetic acid

THE VELOCITY AND MECHANISM OF RACEMIZATION. II. MANDELIC ACID

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTTHE VELOCITY AND MECHANISM OF RACEMIZATION. II. MANDELIC ACIDAlan Newton Campbell and Alexandra Jean Robson CampbellCite this: J. Am. Chem. Soc. 1932, 54, 12, 4581–4585Publication Date (Print):December 1, 1932Publication History Published online1 May 2002Published inissue 1 December 1932https://doi.org/10.1021/ja01351a012RIGHTS & PERMISSIONSArticle Views172Altmetric-Citations4LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (318 KB) Get e-Alerts Get e-Alerts

CXXII.—The mechanism of the racemisation of some hydroxy-acids by heat

CXXII.—The mechanism of the racemisation of some hydroxy-acids by heat