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Topic: Stereoisomerism

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	Stereoisomers
		The essential requirement for this stereoisomerism is that each carbon of the double bond must have two different substituent groups (one may be hydrogen).
		In the next two examples, each double bond carbon atom has two different substituent groups and stereoisomerism exists, regardless of whether the two substituents on one carbon are the same as those on the other.
		The importance of such three-dimensional descriptive formulas became clear in discussing configurational stereoisomerism, where the relative orientation of atoms in space is fixed by a molecule's bonding constitution (e.g.
	www.cem.msu.edu /~reusch/VirtualText/sterisom.htm (2189 words)

	Stereoisomers : Stereoisomerism
		In stereoisomerism, the molecules have the same molecular formula and the same structural formula (the atoms are connected in the same order in each molecule).
		There are two main types of stereoisomerism as shown in Figure 1.
		In this Topic, we will concentrate on stereoisomerism in organic compounds, although this phenomenon also occurs in other compounds such as transition metal complexes.
	scholar.hw.ac.uk /site/chemistry/topic3.asp?outline=no (101 words)

	Stereoisomers
		Other examples of this kind were encountered, and suspicions of a subtle kind of stereoisomerism were confirmed by the different interaction these compounds displayed with plane polarized light.
		We now know that this configurational stereoisomerism is due to different right and left-handed forms that certain structures may adopt, in much the same way that a screw may have right or left-handed threads but the same overall size and shape.
		A stereogenic center is a focus of stereoisomerism, such that an interchange of two groups attached to the atom constituting the center leads to a stereoisomer.
	www.cem.msu.edu /~reusch/VirtualText/sterism2.htm (3790 words)

	Dorlands Medical Dictionary (Site not responding. Last check: 2007-10-20)
		Stereoisomers are further classified into enantiomers, those having molecules that are mirror images of each other, and diastereomers, those that do not.
		An older classification used the subdivisions optical and geometric isomerism (q.v.), which did not include all forms of stereoisomerism.
		Stereoisomerism, exemplified by a pair of cis-trans diastereomers.
	www.mercksource.com /pp/us/cns/cns_hl_dorlands.jspzQzpgzEzzSzppdocszSzuszSzcommonzSzdorlandszSzdorlandzSzdmd_s_23zPzhtm (3508 words)

	[No title] (Site not responding. Last check: 2007-10-20)
		Optical isomerism is a form of isomerism (specifically stereoisomerism) whereby the different 2 isomers are the same in every way except being non-superimposable mirror images(*) of each other.
		First discovered by Louis Pasteur in the nineteenth century, the study of optical isomerism is called stereochemistry.
		Optical isomers are often called stereoisomers (in fact, stereoisomers constitute a more general group, since stereoisomerism needn't necessarily imply optical activity).
	www.askmytutor.co.uk /o/op/optical_isomerism.html (783 words)

	Isomerism (Site not responding. Last check: 2007-10-20)
		2), depending upon the hybridization state and geometry of the atoms that impart the properties of stereoisomerism and the overall structure of the molecule.
		Conformational isomers (conformers) are stereoisomeric forms characterized by different relative spatial arrangements of atoms that result from rotation about sigma bonds.
		The nature of conformational and configurational stereoisomerism, as well as the role of stereoisomerism in drug activity is the subject of this article.
	www.dekker.com /sdek/50729601-53686842/abstract~content=a713491664~db=enc (3381 words)

	isomer on Encyclopedia.com
		Stereoisomerism occurs when two or more molecules have the same basic arrangement of atoms in their molecules but differ in the way the atoms are arranged in space.
		The first type, geometric isomerism, may occur when a compound contains a double bond or some other feature that gives the molecule a certain amount of structural rigidity.
		The second type of stereoisomerism is optical isomerism.
	www.encyclopedia.com /html/i1/isomer.asp (1151 words)

	Aphasia Interview
		The sheer range of sounds on Stereoisomerism was impressive, particularly the fact that nothing seems out of place.
		In particular, I suppose Stereoisomerism was quite satisfactory, being the most accessible work I've done without compromising any elements.
		Stereoisomerism also makes plenty of use of other music, such as hymns sung in French or folk accordion music, both left untreated and sometimes grossly distorted.
	media.hyperreal.org /zines/est/intervs/aphasia.html (2194 words)

	Isomer
		As an example, glucose, while maintaining its basic structure, can arrange its atoms or functional groups in a number of different, spatial arrangements, forming a number of isomers of glucose, with different properties.
		That such a small difference in a molecule can be of great significant is indicated by the different properties the optically active molecules of thalidomide and LSD molecules can have.
		A conformational isomer is another form of stereoisomerism.
	www.monashscientific.com.au /Isomer.htm (497 words)

	Monosaccharides (Site not responding. Last check: 2007-10-20)
		All sugars are referred to these two isomers in order to classify the sugar D or L. In biological systems the D-isomer predominates.
		However the ring structure makes stereoisomerism more complicated because C1, which was not chiral in linear form now becomes chiral, and we have another two optically active stereoisomers.
		-anomer, and a feature of this stereoisomerism, due to ring structure, is that the two isomers are readily interconvertible.
	www-biol.paisley.ac.uk /courses/stfunmac/glossary/monosaccharide.html (730 words)

	R and S
		A grouping within a molecular entity that may be considered a focus of stereoisomerism.
		At least one of these must be present in every enantiomer (though the presence of stereogenic units does not conversely require the corresponding chemical species to be chiral).
		A chemical reaction (or reaction sequence) in which one or more new elements of chirality are formed in a substrate molecule and which produces the stereoisomeric (enantiomeric or diastereoisomeric) products in unequal amounts.
	www.chem.qmul.ac.uk /iupac/stereo/RS.html (1394 words)

	geometric (cis / trans) isomerism
		Geometric isomerism (also known as cis / trans isomerism) is a form of stereoisomerism.
		Structural isomerism is not a form of stereoisomerism, and is dealt with on a separate page.
		In stereoisomerism, the atoms making up the isomers are joined up in the same order, but still manage to have a different spatial arrangement.
	www.chemguide.co.uk /basicorg/isomerism/geometric.html (1640 words)

	Stereoisomerism and Equilibrium Properties of Oxygen-Carrying Cobalt(II) Complexes of Histamine and Its Derivatives: A ...
		Stereoisomerism and Equilibrium Properties of Oxygen-Carrying Cobalt(II) Complexes of Histamine and Its Derivatives: A New Approach to an Old System
		H-NMR study revealed stereoisomerism of oxygenated species in the same protonation states, undergoing slow ligand exchange.
		They also showed the stabilizing effect of the deprotonated amide nitrogen in the oxygenated complexes of pseudopeptides.
	pubs.acs.org /cgi-bin/abstract.cgi/inocaj/1997/36/i09/abs/ic960832r.html (240 words)

	Stereoisomers : Stereoisomerism : Geometric isomerism
		SCHOLAR : Chemistry : 1 Stereoisomers : 1.2 Stereoisomerism :
		Geometric isomerism can arise when there is lack of free rotation around a bond, often a C
		On the other hand, trans-butenedioic acid cannot eliminate water under the same conditions since the two carboxyl groups are on opposite sides of the double bond (Figure 6).
	scholar.hw.ac.uk /site/chemistry/topic4.asp?outline= (208 words)

	Effect of stereoisomerism on the cellular pharmacology of beta-enantiomers of cytidine analogs in Hep-G2 cells.
		Effect of stereoisomerism on the cellular pharmacology of beta-enantiomers of cytidine analogs in Hep-G2 cells.
		The state of the art may have changed since the publication date.
		The higher intracellular 5'-triphosphate levels of beta-L-FddC and the extended T1/2 of its 5'-triphosphate are consistent with the more potent in vitro antiviral activity of beta-L-FddC in Hep-G2 cells when compared with its beta-D enantiomer, beta-D-FddC.
	www.aegis.com /aidsline/1997/mar/M9730822.html (526 words)

	chem 341 (Site not responding. Last check: 2007-10-20)
		Cycloalkanes, including nomnclature and stereoisomerism in the cis- and trans-disubstituted cyclohexanes, and conformational isomerism.
		In preparation for the 2nd experiment in the laboratory (molcular models) you should read ahead into Brown Chapter 4 (Chapter 5 in the 1st edition): optical activity, stereoisomerism, chirality, enantiomers, diastereomers, meso compounds, racemic mixtures and the R- and S-system of describing absolute stereochemistry.
		The modern designation of such configurational isomers uses stereochemical descriptors (E)-, and (Z)- and we will see how these are incorporated into the rational (IUPAC) names for alkenes (see Brown 5..1-5.2 in the 2nd edition, 3.1-3.2 in the 1st edition).
	www.chem.ucalgary.ca /undergrad/courses/f01/chem341/teaching/tutorial.html (3048 words)

	Chem 261 — Organic Chem I (Site not responding. Last check: 2007-10-20)
		Recognize when double bond stereoisomerism is possible and be able to draw the stereoisomers.
		When stereoisomerism is possible, be able to assign the stereochemistry as E or Z. This requires an ability to properly apply the CIP priority rules.
		Be able to assign the stereochemistry as cis or trans when the meaning of these labels is clear.
	www-unix.oit.umass.edu /~gjsnyder/Chs67.html (996 words)

	Re: Does citric acid show any form of stereoisomerism?
		I realise that citric acid is not chiral, and that is has no geometrical isomerism, though I am unsure of the term conformational isomerism.
		Citric acid shows no stereoisomerism at all beyond conformational isomers, which are interconverted by rotating about carbon-carbon single bonds.
		However, other compounds in the citric acid cycle, notably isocitric acid and malic acid, do show stereoisomerism.
	www.madsci.org /posts/archives/dec2001/1009553415.Ch.r.html (142 words)

	Ch110_Lec 34_21 November
		The stereoisomerism of complex ions can be organized by coordination number, with the most important coordination numbers for stereoisomers being 2, 4, and 6.
		MABCD: With four different ligands a new type of stereoisomerism occurs - enantiomerism or optical isomerism (so-called because the mirror-image (chiral) isomers have different optical (polarization) properties).
		With four different ligands can be arranged to give two different isomers which are mirror images of each other.(models).
	www.humboldt.edu /~rap1/C110.F03/C110Notes/C110_lec34.htm (490 words)

	Table of Contents
		Molecular shape, form, and symmetry play a central role in organic chemistry, and this book presents a brief introduction to the conceptual basis of stereochemistry.
		The three-part text deals with structure and symmetry; stereoisomerism; and the separation and configuration of stereoisomers.
		STEREOISOMERISM 2-1 Classification of Structural Isomerism-Enantiomeric and Diastereomeric Relationships 2-2 Optical Activity 2-3 Diastereomers and Racemic Forms 2-4 Torsional Stereoisomerism 2-5 Stereoisomerism Resulting from Asymmetric Atoms-Designation of Configuration at Asymmetric Atoms 2-6 Torsional Stereoisomerism in the Presence of Asymmetric Atoms 2-7 Macromolecules 2-8 Topological Isomerism 2-9 Exercises 3.
	www.doverpublications.com /cgi-bin/toc.pl/0486425304 (304 words)

	Enantiomerism from Okanagan University College: TEST (Site not responding. Last check: 2007-10-20)
		The simplest example of stereoisomerism is given by the two isomers of but-2-ene:
		Because it is not possible to rotate about the C,C double bond at ambient temperature, and because of the planar nature of the C,C double bond, the arrangement of the methyl groups and hydrogen atoms on each end of the double bond is fixed in one of two positions shown by the two rotatable images.
		This type of stereoisomerism is more difficult to imagine, but a pair of illustrations will allow you to begin to see the difference between the isomers:
	crpp0001.uqtr.uquebec.ca /COR/Enantiomerism.htm (247 words)

	Alkenes - Elimination
		A sample of one of these compounds does not become the other, since to do so would require breaking the pi bond and there isn't enough energy available to do that.
		Since the difference is one of spatial arrangement, this is a type of stereoisomerism.
		The absence of rotation about the double bond explains why there are two different 2-butene molecules.
	chemistry2.csudh.edu /rpendarvis/AlkeneElim.html (1675 words)

	Proteins. Alpha amino acids in 3D
		In some cases a pair of molecules that share the same sequence of atoms can have different arrangements in space called configurations.
		-amino acids display a particular type of stereoisomerism that comes from the molecules being
		This means that the two arrangements of the molecules are non-identical mirror images, in the same way that your left hand is a non-identical mirror image of your right hand (see Figure 1).
	www.schoolscience.co.uk /content/5/chemistry/proteins/Protch2pg1.html (383 words)

	Assigning Stereochemistry
		When there are multiple substituents on a ring.
		If either C atom in a double bond contains the same two groups there is NO stereoisomerism possible.
		Divide the double bond as shown to determine cis/trans and E/Z. If both of the groups are in the same color region then they are said to be cis.
	www.csubak.edu /chemistry/nom/stereo.html (373 words)

	Erowid Yerba Mate Vault : Does Yerba Mate contain caffeine or mateine?
		The IUPAC Compendium of Chemical Terminology defines axial chirality as a term used to refer to stereoisomerism resulting from the non-planar arrangement of four groups in pairs around a chirality axis.
		Caffeine does not have a chirality axis and thus cannot have axial chirality.
		IUPAC defines "planar chirality" as a term used by some authorities to refer to stereoisomerism resulting from the arrangement of out-of-plane groups with respect to a plane (chirality plane).
	www.erowid.org /plants/yerba_mate/yerba_mate_chemistry1.shtml (1020 words)

	[No title]
		stereoisomerism (ability of one stereoisomer, but not another, to occupy an active site)
		Which chemistry objectives are chosen to be promoted will determine when in the course this unit is useful and the manner in which the unit is used.
		(b) carry out self study related to functional groups, catalysis, stereoisomerism and/or partition coefficient
	icase.unl.edu /i_exemp2.htm (5356 words)

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