Image Isomerism.png thumb right 350px The different types of isomer s. Stereochemistry focuses on stereoisomer s Stereochemistry , a subdiscipline of chemistry , involves the study of the relative spatial arrangement of atom s within molecule s. An important branch of stereochemistry is the study of chirality chemistry chiral molecules. ref JerryMarch ref Stereochemistry is also known as Three dimensional space 3D chemistry because the prefix stereo means three dimensionality . ref http dictionary.reference.com browse stereo ref The study of stereochemical problems spans the entire range of Organic chemistry organic , Inorganic chemistry inorganic , Biochemistry biological , Physical chemistry physical and Supramolecular chemistry supramolecular chemistries. Stereochemistry includes methods for determining and describing these relationships the effect on the physics physical or biology biological properties these relationships impart upon the molecules in question, and the manner in which these relationships influence the reactivity of the molecules in question dynamic stereochemistry . History and significance Louis Pasteur could rightly be described as the first stereochemist, having observed in 1849 that salt s of tartaric acid collected from wine production vessels could rotate plane polarized light , but that salts from other sources did not. This property, the only physical property in which the two types of tartrate salts differed, is due to optical isomerism . In 1874 ... arrangement of the atoms bound to carbon. An infamous demonstration of the significance of stereochemistry ... priority rules are part of a system for describing a molecule s stereochemistry. They rank the atoms ... to be described unambiguously. A Fischer projection is a simplified way to depict the stereochemistry ... stereochemistry References Reflist Organic chemistry Reaction mechanisms Category Stereochemistry ... simple Stereochemistry sk Stereoch mia sr sh Stereohemija fi Stereokemia sv Stereokemi ... more details
In chemistry , dynamic stereochemistry studies the effect of stereochemistry on the reaction rate of a chemical reaction . Stereochemistry is involved in stereospecific reactions stereoselective or asymmetric reactions racemic racemisation processes 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 Chemical kinetics Category Stereochemistry ... more details
Alkane stereochemistry concerns the stereochemistry of alkane s. Alkane Conformational isomerism conformers are one of the subjects of alkane stereochemistry. Conformations Alkane conformers arise from rotation around sp sup 3 sup orbital hybridisation hybridised carbon carbon sigma bond s. The smallest alkane with such a chemical bond, ethane, exists as an infinite number of conformations with respect to rotation around the C C bond. Two of these are recognised as energy minimum staggered conformation and energy maximum eclipsed conformation forms. The existence of specific conformations is due to hindered rotation around sigma bonds, although a role for hyperconjugation is proposed by a competing theory. The importance of energy minimum and energy maximum is seen by extension of these concepts to more complex molecules for which stable conformations may be predicted as minimum energy forms. The determination of stable conformations has also played a large role in the establishment of the concept of asymmetric induction and the ability to predict the stereochemistry of reactions controlled by steric effects. In the example of staggered ethane in Newman projection , a hydrogen atom on one carbon atom has a 60 torsional angle or torsion angle ref Gold Book http www.iupac.org goldbook T06406.pdf Link ref with respect to the nearest hydrogen atom on the other carbon so that steric hindrance is minimised. The staggered conformation is more stable by 12.5 joule kJ mole unit mol than the eclipsed conformation, which is the energy maximum for ethane. In the eclipsed conformation the torsional angle is minimized. File Staggered and eclipsed.svg center 338px staggered conformation left, eclipsed conformation right in Newman projection center Image Ethane staggered depth cue 3D balls.png ... changes the stereochemistry from the zigzag geometry to that of a helix due to electrostatic ... interactions see Gauche effect . References Reflist DEFAULTSORT Alkane Stereochemistry Category Stereochemistry ... more details
In the stereochemistry of ketonization of enols and enolates , theory is provided explaining the diastereoselectivity ref Name Selectivity a Overlap Control of Carbanionoid Reactions. I. Stereoselectivity in Alkaline Epoxidation, Zimmerman, H. E. Singer, L. Thyagarajan, B. S. J. Am. Chem. Soc., 1959, 81, 108 116. b Eliel, E., Stereochemistry of Carbon Compound , McGraw Hill, 1962 pp 434 436. ref observed in the conversion of certain enol s and enolate s into the corresponding ketone. Introduction Ketone s and their corresponding enol s are isomer s, termed tautomers . These are easily interconvertible. But simple enols are not generally stable and of considerably higher energy than the corresponding ... s on ketonization. If one knows the stereochemistry of ketonization of these enolic intermediates, then one can predict the stereochemistry of a myriad of organic reaction s. It was proposed in 1955 ref name HEZ 1955 The Stereochemistry of the Ketonization Reaction of Enols, Howard Zimmerman ... name HEZ 1956 a The Stereochemistry of the Ketonization Reaction of Enols. III, Zimmerman, H. E. Giallombardo, H. J. J. Am. Chem. Soc. , 1956, 78, 6259 6263. ref ref name HEZ1957 b The Stereochemistry ... 1959 c The Stereochemistry of Ketonization. X. Enols from alpha Haloacids, Zimmerman, H. E. Cutshall ... in the Stereochemistry of Ketonization of Enols , Zimmerman, H. E. Linder, L. W. J. Org. Chem. , 1985,c48, 1637 1646. ref ref name HEZ 1987 e Kinetic Protonation of Enols, Enolates and Analogs The Stereochemistry ... name HEZ 2006 f The Stereochemistry of Allenic Enol Tautomerism Independent Generation and Reactivity ... of the stereochemistry of kinetic protonation of an enol ref name Linder With an Acid catalysis ... stereochemistry. ref name HEZ 2002 Figure 3. Two Phenyl Pyridyl Enol Diastereomers. Image PhenylPyridyl.gif ... of the less stable cis product. ref The Stereochemistry of Protonation. XI, Zimmerman, H. E. Mariano, P. S., J. Am. Chem. Soc., 1968, 90, 6091 6096. ref References references Reflist Category Stereochemistry ... more details
Anticlinal may refer to Anticline , in structural geology, an anticline is a fold that is convex up and has its oldest beds at its core. Anticlinal, in stereochemistry, a torsion angle between 90 to 150 , and 90 to 150 see Alkane stereochemistry See also Weald Artois Anticline Mareuil Anticline La Tour Blanche Anticline Usk Anticline Fold geology Detachment fold Stereochemistry disambig ... more details
Orphan date February 2009 refimprove date September 2008 Mechanostereochemistry is the stereochemistry of the molecules with mechanical bonds. This concept was first introduced by Sir J Fraser Stoddart, a chemistry professor at Northwestern University, Evanston, IL. References http blogs.nature.com thescepticalchymist 2008 08 acs philadelphia 2008 the boss.html http stoddart.northwestern.edu Category Stereochemistry ... more details
NMR database NMR nuclear magnetic resonance may refer to NMR spectra database , a collection of NMR spectra for a large number of compounds NMR database method , a strategy to identify the stereochemistry of certain chiral compounds dab ... more details
Unreferenced date March 2007 Stereoelectronics is the study of the interplay between the electronic structure and geometry of a molecule . For example, in the case of reactant molecules with Chirality chemistry chiral isomer s the electron distribution can determine the stereochemistry of the reactions of the different diastereomer s. Categories Category Organic chemistry Category Quantum mechanics chemistry stub fi Stereoelektroniikka ... more details
Synclinal may refer to Syncline , in structural geology, a syncline is a fold, with younger layers closer to the center of the structure. Synclinal , in alkane stereochemistry, a torsion angle between 30 to 90 and 30 to 90 See also Homocline Newman projection Detachment fold Gauche effect disambig ... more details
wiktionary gauche Gauche can refer to Gauche Scheme implementation , an implementation of the Scheme programming language Scheme programming language . In stereochemistry , Alkane stereochemistry gauche refers a specific conformer . Gauche Effect hinders chemical bond bond rotation. A style of Western fencing using the Main gauche . In Paris , the Rive Gauche is on the southern bank of the Seine. Awkward or lacking in social graces from French, gauche generally means left or awkward , see wiktionary gauche The main character in the short story Gauche the cellist . See also Left disambiguation disambig ... more details
For the geometry of staggered rows lattice group context date March 2011 Image Staggered Conformation.svg thumb 200px Staggered conformation image right in Newman projection Image Eclipsed Conformation.svg 200px thumb Eclipsed conformation Image Ethane conformation.gif thumb right 200px conformational freedom in ethane In organic chemistry, a staggered conformation is a chemical conformation of an ethane like moiety abcX Ydef in which the substituents a,b,and c are at the maximum distance from d,e,and f. This requires the torsion angles to be 60 . ref Ernest L. Eliel and Samuel H. Wilen, Stereochemistry of Organic Compounds , Wiley 1994 , p.1207 ref Such a conformation exists in any open chain single chemical bond connecting two sp sup 3 sup orbital hybridisation hybridised atoms, and is normally a conformational energy minimum .For some molecule s such as those of n butane , there can be special versions of staggered conformations called gauche and anti see first Newman projection diagram in Conformational isomerism . See also Alkane stereochemistry References Reflist DEFAULTSORT Staggered Conformation Category Stereochemistry ar nl Geschrankte conformatie sr Stepeni asta konformacija sv Staggered ... more details
Unreferenced date December 2009 Orphan date December 2009 Cryptoregiochemistry refers to the site of initial oxidative attack in double bond formation by enzymes such as fatty acid desaturase s. This is a mechanistic parameter that is usually determined through the use of kinetic isotope effect experiments, based on the premise that the initial C H bond cleavage step should be energetically more difficult and therefore more sensitive to isotopic substitution than the second C H bond breaking step. Category Chemical kinetics Category Stereochemistry ... more details
RTI 352 is a phenyltropane that is used as a radiolabeling ligand for the Dopamine active transporter DAT . US Patent 6358492 RTI 352 has been configured to have 1 R ,2 S ,3 R stereochemistry and is therefore a geometric isomer of CIT . Based on X ray crystallography, this compound is in a tautomer ic equilibrium residing mostly on the side of the boat shaped conformer. Die synthesis runs as follows File Boat tropane synth.png 800px Phenyltropanes Category Tropanes Category RTI compounds ... more details
Wiktionary cline cline Cline may refer to Scientific concepts related to change Cline biology Cline hydrology Cline linguistics Cline mathematics Clinal, in alkane stereochemistry , a torsion angle between 30 and 150 or between 30 and 150 Other Cline, generalised circle , in geometry Cline the NATO reporting name for the Antonov An 32 Cline surname Clinitrachus argentatus , known as Cline in the UK See also Clyne disambiguation Kline disambiguation Klein disambiguation disambig de Cline fr Cline ... more details
The Natta projection is a way to depict molecules with complete stereochemistry in two dimensions in a skeletal formula . This concept is named after Giulio Natta . In a hydrocarbon molecule with all carbon atoms making up the backbone in a tetrahedral molecular geometry , the zigzag backbone is in the paper plane with the substituents either sticking out of the paper chemical bond depicted triangular in bold or retreating into the paper chemical bond depicted triangular in stripe pattern . The Natta projection is useful for representing the tacticity of a polymer. Image Isotacticpolymer.gif center isotactic polymers See also Haworth projection Newman projection Fischer projection References cite book title Polymer Synthesis Theory and Practice Fundamentals, Methods, Experiments author Dietrich Braun, Harald Cherdron, Matthias Rehahn, H. Ritter, B. Voit publisher Springer year 2005 isbn 3540207708 page 10 Category Stereochemistry ar es Proyecci n de Natta it Proiezione di Natta he hu Natta projekci ru ... more details
The configuration of a molecule is the permanent geometry that results from the space spatial arrangement of its chemical bond bonds . The ability of the same set of atoms to form two or more molecules with different configurations is stereoisomerism . Used as drugs, compounds with different configuration normally have different physiological activity, including the desired pharmacological effect, the toxicology and the metabolism. ref name Ariens Everhardus Ari ns Stereochemistry, a basis for sophisticated nonsense in pharmacokinetics and clinical pharmacology , European Journal of Clinical Pharmacology 26 1984 663 668, DOI 10.1007 BF00541922 . ref Configuration is distinct from chemical conformation , a shape attainable by bond rotation s. See also Chemical conformation Absolute configuration External links http www.iupac.org goldbook C01249.pdf The IUPAC definition of configuration References references chem stub Category Molecules Category Stereochemistry de Konfiguration Chemie fa he nl Configuratie scheikunde ru sv Konfiguration ... more details
Image Sulfur tetrafluoride 2D dimensions.png thumb Sulfur tetrafluoride has a steric number of 5. The steric number of a molecule is the number of atoms bonded to the central atom of a molecule plus the number of lone pairs on the central atom. It is often used in VSEPR theory valence shell electron pair repulsion theory in order to determine the particular shape, or molecular geometry , that will be formed. Steric number in VSEPR Calculating the steric number of a molecule s central atom is a vital step in figuring out its geometry. On the molecule Sulfur tetrafluoride SF sub 4 sub , for example, the central sulfur atom has four ligands about it, calculated by considering sulfur s coordination number . In addition to the four ligands, sulfur also has one remaining lone pair expanded octet does not apply in this compound . Thus, the steric number is 5. Comparing a central atom s steric number to the number of ligands not counting lone pairs allows one to figure out the geometry of that central atom. See also AXE method Stereochemistry Category Stereochemistry Category Molecular geometry chemistry stub ko it Numero sterico ... more details
In chemistry, antipode is synonymous with optical antipode . An optical antipode is the same as an enantiomer . A solution of enantiomer rotates plane polarized light in a certain direction. A solution of the opposite enantiomer, the antipode, Optical rotation rotates plane polarized light in the opposite direction. The Glossary of chemistry terms chemical term antipode is considered obsolete , and its use is discouraged. Citation needed date October 2010 However, the term antipode can still be found in modern day chemistry journals. The modern day approved term for both antipode and optical antipode is enantiomer . ref http www.chemicool.com definition antipodes.html ref ref The Stereochemistry of Organic Compounds , Eliel, E. L. Wilen, S. H., Wiley Interscience, New York, 1994 , 1203. ISBN 0 471 01670 5, QD481.E52115 1993 ref See also Optical rotation References reflist DEFAULTSORT Antipode Chemistry Category Stereochemistry ... more details
In chemistry the intimate ion pair concept introduced by Saul Winstein describes the interactions between a cation , anion and surrounding solvent molecules . ref cite journal last Winstein first S. coauthors Clippinger, E. Fainberg, A. H. Heck, R. RobinsonG. C. year 1956 title Salt Effects and Ion Pairs in Solvolysis and Related Reactions. III.1 Common Ion Rate Depression and Exchange of Anions during Acetolysis volume 78 issue 2 pages 328 335 issn DOI 10.1021 ja01583a022 doi 10.1021 ja01583a022 journal Journal of the American Chemical Society ref In ordinary aqueous solutions of inorganic salts an ion is completely solvated and shielded from the counterion. In less Chemical polarity polar solvents two ions can still be connected to some extent. In a tight or intimate or contact ion pair there are no solvent molecules between the two ions. When solvation increases, ionic bonding decreases and a loose or solvent shared ion pair results. The ion pair concept explains stereochemistry in solvolysis . The concept of intimate ion pairs is used to explain the slight tendency for inversion of stereochemistry during an SN1 reaction . It is proposed that solvent or other ions in solution may assist in the removal of a leaving group to form a carbocation which reacts in an SN1 fashion similarly, the leaving group may associate loosely with the cationic intermediate. The association of solvent or an ion with the leaving group effectively blocks one side of the incipient carbocation, while allowing the backside to be attacked by a nucleophile. This leads to a slight excess of the product with inverted stereochemistry, whereas a purely SN1 reaction should lead to a racemic product. See also Ion association References reflist Category Chemical bonding ... more details
Desymmetrization in stereochemistry is the modification of a molecule that results in the loss of one or more symmetry elements. An important application involves the introduction of chirality chemistry chirality . Formally, such conversion require the loss of an improper axis of rotation mirror plane, center of inversion, rotation reflection axis . In other words, desymmetrizations convert prochiral precursors into a Chirality chemistry chiral products. ref Basic Terminology of Stereochemistry , G.P. Moss Ed. Pure Appl. Chem., Vol. 68, No. 12, pp. 2193 2222, 1996 . ref Examples One example is the conversion of cis 3,5 diacetoxycyclopentene to its the monoacetate. In this transformation, the plane of symmetry in the precursor is lost, and the product is asymmetric. The desymmetrization itself is not usually considered useful. The enantioselective desymmetrization however delivers a useful product. This particular conversion utilizes the enzyme cholinesterase . ref Donald R. Deardorff, Colin Q. Windham, and Chris L. Craney Enantioselective Hydrolysis of cis 3,5 Diacetoxycyclopentene 1R,4S 4 Hydroxy 2 cyclopentenyl Acetate Organic Syntheses, Coll. Vol. 9, p.487 1998 Vol. 73, p.25 1996 . ref File DesymDiacetate.png 300px In another example, transfer hydrogenation converts benzil PhC O C O Ph into one enantiomer of hydro benzoin ref OrgSynth author Takao Ikariya, Shohei Hashiguchi, Kunihiko Murata, and Ry ji Noyori title Preparation of Optically Active R,R Hydrobenzoin from Benzoin or Benzil vol 82 pages 10 year 2005 prep v82p0010 ref PhC O C O Ph 2 H sub 2 sub PhCH OH CH OH Ph The precursor benzil has C sub 2v sub symmetry group symmetry , and the product has C sub 2 sub symmetry. References Reflist Category Stereochemistry fr D sym trisation ... more details
notability date August 2011 primary sources date August 2011 Infobox Software name BKchem logo File Bkchem48.png screenshot Image BKchem v0.11.6 Mac OS X 10.4.8.png 256px caption BKchem v0.11.6 running under Mac OS X 10.4.8 author Beda Kosata developer Beda Kosata released latest release version 0.13.0 latest release date release date and age 2009 02 23 operating system platform Cross platform programming language Python programming language Python , Tcl Tk genre Scientific license GNU General Public License GNU GPL website http bkchem.zirael.org bkchem.zirael.org BKchem is a free 2D molecule editor written in Python programming language Python by Beda Kosata. As such, it is largely cross platform platform independent . Major features Image Fisetin.svg right thumb Structure drawn with BKchem Drawing Bond by bond drawing Straight and curved arrows Radical chemistry Radicals , lone pair s and Ion charges Templates for drawing common structure users can create their own Simple vector graphics Editing Unlimited undo redo capabilities Aligning, scaling and rotation 2D and 3D Exports to SVG OpenOffice.org Draw OpenOffice Draw PDF Encapsulated PostScript EPS Encapsulated Postscript Molfile Portable Network Graphics PNG with http www.cairographics.org pycairo Pycairo installed SMILES Stereochemistry is not supported InChI with InChI program Imports Molfile SMILES Stereochemistry is not supported InChI Stereochemistry is not supported Other features Searching BKchem files for a molecule or a fragment of a molecule Localization support currently English, French, Czech and Polish translations are available Support for user written plugins Validity checking Can be run from source with Python programming language Python External links portal Free software http bkchem.zirael.org BKchem official website free software stub Category Free software programmed in Python Category Chemistry software de BKChem ... more details
Antarafacial and suprafacial are two topology topological concepts in organic chemistry describing the relationship between two simultaneous chemical bond making and or bond breaking processes in or around a reaction center. ref IUPAC Gold Book definition http www.iupac.org goldbook A00377.pdf Link ref The reaction center can be a p orbital , a conjugated system or even a sigma bond . This relationship is antarafacial when opposite faces are involved think anti . It is suprafacial when both changes occur at the same face. Many sigmatropic reaction s and cycloaddition s can be either suprafacial or antarafacial, and this determines the stereochemistry . An example is the 1,3 hydride shift, in which the interacting frontier orbital s are the allyl free radical and the hydrogen 1s orbitals. The suprafacial shift is Woodward Hoffmann rules symmetry forbidden because orbitals with opposite algebraic signs overlap. The symmetry allowed antarafacial shift would require a strain energy strained transition state and is also unlikely. In contrast a symmetry allowed and suprafacial 1,5 hydride shift is a common event. ref F.A. Carey, R.J. Sundberg, Advanced Organic Chemistry Part A ISBN 0 306 41087 7 ref Image Antarafacial suprafacial.png 500px Antarafacial suprafacial example References references Category stereochemistry de Suprafacial und Antarafacial pl Antarafacjalny suprafacjalny ... more details
Orphan date January 2011 The NMR database method enables identification of the stereochemistry of chirality chemistry chiral molecules, especially polyol s. It relies on the observation that NMR spectroscopy data depend only on the immediate environment near an asymmetric carbon , not on the entire molecular structure. All stereoisomers of a certain class of compounds are synthesized, and their proton NMR and carbon 13 NMR chemical shift s and coupling constant s are compared. Yoshito Kishi s group at Harvard University has reported NMR databases for 1,3,5 triols ref Kobayashi, Y. Tan, C. H. Kishi, Y . Toward Creation of a Universal NMR Database for Stereochemical Assignment The Case of 1,3,5 Trisubstituted Acyclic Systems Helv. Chim. Acta 2000, 83, 2562 2571. ref 1,2,3 triols, 1,2,3,4 tetraols, and 1,2,3,4,5 pentaols. ref S. Higabayashi, W. Czechtizky, Y. Kobayashi, and Y. Kishi . Universal NMR Databases for Contiguous Polyols. J. Am. Chem. Soc. 2003, 125, 14379 14393. ref The stereochemistry of any 1,2,3 triol may be determined by comparing it with the database, even if the remainder of the unknown molecule is different from the database template compounds. References reflist Category Spectroscopy Category Nuclear magnetic resonance analytical chem stub ... more details
wiktionary anti anti Anti may refer to Anti mythology , the ferryman who carried Isis to Set s island in Egyptian mythology Anti, or Campa , a tribe of South American Indians ANTI Contemporary Art Festival , a yearly international live art festival held in Kuopio, Finland ANTI , an American independent record label Antiparticle , a particle with the same mass but opposite charges in particle physics Anti addition in organic chemistry Anti EP , an EP by Autechre Anti conformation in alkane stereochemistry See also Ante disambiguation Opposition disambiguation Opposite disambiguation Special Prefixindex Anti an automatically generated list of pages beginning with anti intitle disambig da Anti de Anti it Anti pt Anti sq Anti fi Anti ... more details
Encyclopedia
top
