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Topic: Chair conformation

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	Cyclohexane - Wikipedia, the free encyclopedia
		In the lowest-energy chair conformation, half of the 12 hydrogens are in axial positions, which means their C-H bonds are parallel and appear to stick up and down from the structure, the other half are in equatorial positions; meaning that they are splayed out.
		Only the twist form is isolable as - like the chair form - it represents an energy minima, although of a higher energy than the chair form due to increased torsional strain when compared to the chair form.
		The boat and half-chair forms are transition states between the twist forms and the twist and chair forms respectively, and are impossible to isolate.
	en.wikipedia.org /wiki/Cyclohexane (432 words)

	C (Site not responding. Last check: 2007-11-05)
		Chair, Boat, Twist - If carbon atoms 1, 2, 4 and 5 of cvclohexane occupy coplanar positions and when carbon atoms and 6 are on opposite sides of the plane the conformation (of symmetry group D3d) is called a chair form.
		Conformational Analysis - The assessment of the relative energies (or thermodynamic stabilities), reactivities, and physical properties of alternative conformations of a molecular entity, usually by the application of qualitative or semi-quantitative rules or by semi-empirical calculations.
		It is analogous to the chair conformation of cyclohexane.
	www.sdsc.edu /Education/Elemnet/misc/newerglossary/c.html (1358 words)

	CHAPTER 6
		Conformation is a spatial arrangement of a molecule of a given constitution and configuration.
		The rate of conformational changes can be further lowered by involvement of the NH group in hydrogen bonding with neighbouring molecules (formation of dimers, etc.) or fragment of the same molecules, giving rise to rigid conformers (alpha-helix, beta-sheet of protein).
		Conformation of saturated six-membered rings is important in view of the fact that they are key building block of most carbohydrates and are also featured in such compounds as inositol phosphates and cyclic 3',5'-nucleoside phosphates.
	tigger.uic.edu /~kbruzik/text/chapter6.htm (1977 words)

	Chair conformation Definition / Chair conformation Research (Site not responding. Last check: 2007-11-05)
		Chair conformation is a term used for the most stable chemical structure of a six member single bonded carbon ring.
		chair conformation is the most energetically stable of all different forms of the ring.
		chair conformation is the conformation with the lowest energy, and is therefore the most stable conformation.
	www.elresearch.com /Chair_conformation (201 words)

	Alkane Conformation (Site not responding. Last check: 2007-11-05)
		The conformational flexability of cyclohexane is somewhat unique in that two equivalent structures are involved which are linked by a process termed "ring inversion".
		The explanation for this fact is that the flexability of cyclohexane allows for rapid ring inversion, in which one chair conformation is replaced by a second.
		In the axial conformation, however, the van der Waals radii of the bromine significantly overlaps with that of the two axial hydrogens.
	chipo.chem.uic.edu /web1/ocol/SB/2-3.htm (987 words)

	bk6
		In the "eclipsed" conformer, the atoms are "aligned", similar to the moon eclipsing the sun.
		One principal conformation is the "chair form" or "chair conformation" shown in 19a.
		A second "chair form" 19b is also possible, The two "chair forms" 19a and 19b are in equilibrium with one another.
	www.chem.unl.edu /cak/bk6.htm (2957 words)

	[No title]
		In the previous tutorials on conformations, we learned the factors that affect the energy (stability) of conformations as a result of rotation around a C-C bond of acyclic (non-cyclic) alkanes.
		The most stable conformation of cyclohexane is the chair conformation, in which all bond angles are close to the tetrahedral 109°.
		As cyclohexane goes from one chair conformation to the other (note that the two chairs are equivalent), it has to go through several other forms (conformations): half-chair, twist boat, and boat.
	www.uwosh.edu /faculty_staff/xie/tutorial/cycloalkane_conf.htm (481 words)

	[No title]
		These conformations were commonly represented by the so-called 'sawhorse'projection in which the C-C bond is artificially elongated so that the relative orientations of the C-H bonds can be displayed (Fig 1.13); however, this has been largely superseded by the use of the Newman projection.
		In Fig 1.14 theta is the dihedral or torsion angle and is 60 deg in staggered conformation and 0 deg in the eclipsed conformation.
		The synperiplanar conformer is the highest-energy and therefore least favoured owing to the close proximity of eight pairs of mutually repulsive bonding electrons, and at the other end of the scale, the antiperiplanar conformer is lowest energy and most favoured as it affords maximum repulsion of all bonding electrons.
	www.ch.ic.ac.uk /GCA/chirality/SRB2.html (1415 words)

	The Force-Driven Conformations of Heparin Studied with Single Molecule Force Microscopy -- Marszalek et al. 85 (4): ...
		chair conformation with the glycosidic bond in the axial orientation.
		chair conformation with the aglycone and glycosidic bonds in the equatorial orientation.
		conformation and the GlcN residue to a boatlike conformation.
	www.biophysj.org /cgi/content/full/85/4/2696 (4914 words)

	DrawingRules
		Students often have difficulty drawing proper chair conformations of molecules that contain 6-membered rings.
		Now that you know how to draw a chair conformation of a 6-membered ring, let's look at the changes that occur during a chair-chair interconversion.
		Select the conformation that would be formed by chair-chair interconversion of structure 1.
	www.usm.maine.edu /~newton/Chy251_253/Lectures/MolecularMotions/DrawingRules.html (422 words)

	ARS \| Publication request: B3lyp/6-311++g*geometry Optimization of the Chair Forms of Alpha and Beta-D-Mannopyranose (Site not responding. Last check: 2007-11-05)*
		The structures of mannopyranose in the 4C1 chair conformation are less than 1.5 to 3 kcal/mol higher in overall energy than the lowest energy glucopyranose conformation that we have found.
		The 4C1 chair conformers of mannopyranose possess a slight preference for the beta-anomer over the alpha-anomer in vacou.
		The lowest energy conformation of mannopyranose in this study is the beta tg rotamer, however, other gg and gt rotamers of mannopyranose are within less than 0.3 kcal/mol in overall energy.
	www.ars.usda.gov /research/publications/publications.htm?SEQ_NO_115=160047 (199 words)

	Stereoisomers
		A careful examination of the axial conformer shows that this steric hindrance is due to two gauche-like orientations of the methyl group with ring carbons #3 and #5.
		The corresponding equilibrium constant is related to the energy difference between the conformers, and collecting such data allows us to evaluate the relative tendency of substituents to exist in an equatorial or axial location.
		In a sample of cyclohexane, the two identical chair conformers are present in equal concentration, and the hydrogens are all equivalent (50% equatorial & 50% axial) due to rapid interconversion of the conformers.
	www.cem.msu.edu /~reusch/VirtualText/sterism2.htm (3672 words)

	World Intellectual Property Organization (Site not responding. Last check: 2007-11-05)
		One embodiment is a method for identifying a compound that binds a native quadruplex DNA, which comprises contacting a test quadruplex DNA in a chair conformation with a candidate compound, and determining the presence or absence of binding between the candidate and the test quadruplex DNA.
		One conformation may be favored over another conformation if it is present in the system at a fraction of 50% or greater, 75% or greater, or 80% or greater or 90% or greater with respect to another conformation (e.
		Nucleic acids in a chair conformation often have similar but not identical structures when compared to one another and differences can manifest in loop size and nucleotide sequence, quadruplex geometry, quadruplex stability, the number of alternative chair structures for a given nucleotide sequence, and chemical reactivity, and binding of other molecules.
	www.wipo.int /ipdl/IPDL-CIMAGES/view/pct/getbykey5?KEY=03/87317.031023&ELEMENT_SET=DECL (10270 words)

	Relative stability of <SUP>1</SUP>C<SUB>4</SUB> and ... (Site not responding. Last check: 2007-11-05)
		conformers the deviations are large because the repulsive eclipsing interactions of the OH groups with the ring C-C bonds is counterbalanced by the O...H interactions and nearly eclipsed rotamers occur.
		conformer of D-glucose provided that the G- and G+ rotamers were populated in about 55:45 ratio at room temperature, while the population of the T rotamer was negligible (less than 2%) [13].
		In these conformers the repulsive eclipsing interactions of the OH groups with the ring C-C bonds is counterbalanced by the O...H interactions and nearly eclipsed rotamers occur.
	web.inc.bme.hu /~csonka/glc/glc.htm (4062 words)

	cyclic alkanes
		The lowest energy arrangement of the atoms in cyclohexane is the chair conformation which is shaped like a patio chair.
		These two chair conformations are equal in energy and the barrier to rotation is small enough that this interconversion occurs readily at room temperature.
		Furthermore, because each conformation has one axial and one equatorial methyl group, the energy of the two conformations is the same.
	people.uis.edu /gtram1/organic/alkanes/cyclicalkanes.htm (1273 words)

	metal bar stools, cafe chairs, folding bar stool - chairs.ws (Site not responding. Last check: 2007-11-05)
		Main index of bar stools, seats, tables, cafe chairs, and complementary for restaurants bars and cafes.
		Slim is a range of chairs for multipurpose rooms, waiting and break areas, which...
		Chairs.ws and all its content, branches and divisions are oficially registered as Nr.15 - 06/05/2004 at the Court of the City of Udine - Italy.
	www.chairs.ws (498 words)

	ORGANIC CHEMISTRY I - CHAPTER 4 LECTURE OUTLINE (Site not responding. Last check: 2007-11-05)
		Anti, eclipsed and gauche conformers formed by rotation.
		Chair forces hydrogen (or substituents) into axial and equatorial positions.
		If the chair "flips," the axial and equatorial assignments are reversed.
	www.sbuniv.edu /~ggray/CHE3304/ocp4outl.html (159 words)

	Theoretical density functional study of substituted dioxanes: trans 3,6-Dimethoxy-1,2-dioxane (Site not responding. Last check: 2007-11-05)
		The synclinal conformer with two anomeric effects and one exo-anomeric effect has the lowest energy, and the difference between both conformers is 4.45 kcal/mol and 1.13 kcal/mol for the AM1 and PM3 semiempirical methods, respectively.
		In the antiperiplanar conformer, the oxygen free-electron pairs corresponding to the methoxyl group are located at an antiperiplanar position with respect to each endo C-O bond.
		In 1,3- and 1,4-dioxanes prevail the diaxial conformations for the disubstituted molecules at the trans position and ΔG > 2 kcal/mol for the diaxial-diequatorial equilibrium.
	www.arkat-usa.org /ark/journal/2003/I15_General/1-332A/1-332A.asp (2236 words)

	Cyclohexane
		Every cyclohexane derivative has two possible chair conformations that interconvert rapidly at room temperature.
		In order for one chair conformation to change into the other it must pass through a boat conformation.
		The two chair conformations are exactly the same for unsubstituted cyclohexane BUT watch carefully to see what happens to 1,2,3,4,5,6-hexadeuterocyclohexane.
	www.csubak.edu /Chemistry/331/cychex/cyclohex.html (214 words)

	[No title] (Site not responding. Last check: 2007-11-05)
		However, it does have torsional strain because the conformation is eclipsed at each of the green bonds.
		The boat conformation is 6 kcal/mol (25 kJ/mol) less stable than the chair conformation.
		The twist boat conformation is 1 kcal/mol (4 kJ/mol) more stable than the boat conformation, but it is still 5 kcal/mol (21 kJ/mol) less stable than the chair conformation.
	www.nsm.du.edu /organic/organic/cycloc6.html (185 words)

	An NMR and theoretical study of the conformation and internal flexibility of butaclamol hydrochloride. (Site not responding. Last check: 2007-11-05)
		An NMR and theoretical study of the conformation and internal flexibility of butaclamol hydrochloride.A theoretical (MM2) and experimental (1H and 13C NMR) study of butaclamol hydrochloride in CDCl3 has been done in order to determine preferred conformations and internal molecular flexibility of this molecule.
		The theoretical calculations suggest the presence of four low-energy conformations, two of which involve a trans junction of the D and E rings, with the other two involving a cis I ring junction.
		The 1H NMR data strongly suggest the presence of a trans D-E ring junction and are consistent with a chair conformation of the E ring.
	www.pdg.cnb.uam.es /UniPub/iHOP/gp/36206.html (182 words)

	ChemViz Cyclohexane Boat and Chair Lab (Site not responding. Last check: 2007-11-05)
		The lower energy is the more natural state for the molecule If the difference between the two conformations is great, the lower energy conformation is the one that the molecule will actually take.
		You may want to also choose the chair conformation and have it on the screen for comparison.
		Use VRML to study the hybridization of the orbitals within the conformations, and of benzene and cyclohexadiene.
	chemviz.ncsa.uiuc.edu /content/lab-s-cyclohex.html (590 words)

	Cyclohexane: Tracing the Chair Conformation
		A model of the chair conformation of cyclohexane is oriented so that its outline reveals the shadow of a chair.
		Tracing the projection of this outline shows how the chair conformation is portrayed on a flat piece of paper.
		Notice there are 2 types of bonds in chair cyclohexane - axial bonds that are perpendicular to the ring and equatorial bonds that are roughly in the plane of the ring.
	www.jce.divched.org /JCESoft/CCA/CCA5/MAIN/1ORGANIC/ORG02/TRAM02/F/0120622/THUMBS.HTM (135 words)

	Skill Development Exercises For Part B
		For each of these, the lowest potential energy conformation is the one with the maximum number of methyl groups in an equatorial position.
		Draw chair representations of the two different chair conformations of trans-1,4-dimethylcyclohexane.
		The trans stereoisomer is inherently lower in potential energy since its lowest energy conformation is more favorable (both methyl groups in equatorial positions) than the lowest energy conformation of the cis stereoisomer (with one methyl group forced into an axial position).
	www.beloit.edu /~chem/Chem230/SDEANS/ANS6B/Ans6B.htm (424 words)

	B and C
		C-C(Y)=X (with identical or different groups R) the conformation in which the torsion angle is such that X is antiperiplanar to one of the groups R, and, in a Newman projection, the double bond C=X bisects one of the R-C-R angles.
		The other conformation, in which X is synperiplanar to one of the groups R, is called an eclipsing conformation.
		In a five-membered ring a conformation in which two adjacent atoms are maximally displaced, in opposite directions, relative to the plane containing the other three carbon atoms has been called a half-chair but is better called a twist conformation (see also envelope conformation).
	www.chem.qmw.ac.uk /iupac/stereo/BC.html (1536 words)

	chapt4 notes (Site not responding. Last check: 2007-11-05)
		Highest energy conformation is eclipsed with all the six C-H bonds as close as possible.
		Gauche conformation—higher in energy than the anti conformation due to the fact that the hydrogen atoms of the methyl groups are near one another resulting in steric strain—repulsive interaction that occurs when atoms are forced closer together than their atomic radii allow
		Energy difference between axial and equatorial conformers is due to steric strain caused by 1,3-diaxial interactions.
	sankofa.loc.edu /peaks/web/chapt4_notes.html (946 words)

	HONORS ORGANIC I
		Indicate which one of the conformations you drew in part b is the most stable.
		Indicate which one of the staggered conformations you drew is the least stable.
		Indicate which one of the chair conformations is more stable.
	www.muhlenberg.edu /depts/chemistry/chem201woh/PEXAMIIFALL02.htm (534 words)

	Computation Chemistry Lab3
		The torsion angles and the bond lengths are of question to determine that we have constructed the correct molecule.
		This study was to understand the differences in the conformational energy of the different forms of these sugars.
		What this shows us is that in the case of both of the sugars the most likely conformer is going to be the chair because it takes the least amount of energy.
	web.syr.edu /~grwestby/molecular/lab3.htm (719 words)

	wiki/Chair conformation Definition / wiki/Chair conformation Research
		The overall structure looks like a chair, and is more stable than the other main configuration which is called the boat formation.
		Categories: Organic chemistryOrganic chemistry is the study of organic, or carbon based, molecules.
		Carbon is the only element that can make bonds with itself so that chains are produced, silicon has similar properties, but Carbon is a main element in everyday life, and thus, is lucky enough to have a whole subject in chemistry dedicated to it....
	www.elresearch.com /wiki/Chair_conformation (153 words)

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