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Topic: Sp2 bonds

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	SP2 - Transcription factor Sp2
		The influence of the sp2 hybridization at C-9 and of the presence of 11, 12-carbonate grouping on the antibacterial activity was shown.
		The degree of SP2 produced by electrical stimulation of the palmar side of the index finger in patients with PD was lower than that in normal subjects, although the degree of SP2 produced by median nerve stimulation in patients with PD did not differ from that in normal subjects.
		SP2 is a homologue of Sp2 (Sp2 transcription factor) from Mus musculus.
	www.pdg.cnb.uam.es /UniPub/iHOP/gg/92338.html (4037 words)

	Hybridisation (Site not responding. Last check: 2007-08-19)
		The bonds between the hydrogen atoms and carbons, and the first bond (of the double bond) between the carbon atoms of ethene are formed by the end-on overlap of these sp1 hybrids orbitals to form sigma bonds, and accounts for the 180 degree bond angles observed in this compound.
		The bonds between the hydrogen atoms and carbons, and the first bond (of the double bond) between the carbon atoms of ethene are formed by the end-on overlap of these sp2 hybrids orbitals to form s bonds (sigma bonds), and accounts for the 120 bond angles observed in this compound.
		The bonds between the hydrogen atoms and carbons, and the first bond (of the double bond) between the carbon atoms of ethene are formed by the end-on overlap of these sp1 hybrids orbitals to form s bonds (sigma bonds), and accounts for the 1800 bond angles observed in this compound.
	www.ucc.ie /ucc/depts/chem/dolchem/html/dict/hybrid.html (1931 words)

	Encyclopedia: SpÂ² bond (Site not responding. Last check: 2007-08-19)
		hybridization most commonly occurs in cases where a Covalent bonding is a form of chemical bonding characterized by the sharing of one or more pairs of electrons between atoms, in order to produce a mutual attraction, which holds the resultant molecule together.
		double bond is going to be formed (as stated above, alkenes are the most frequent example).
		σ bonds a p-type orbital is used for the Geometry of the water molecule Molecules have fixed equilibrium geometries--bond lengths and angles--that are dictated by the laws of quantum mechanics.
	www.nationmaster.com /encyclopedia/Sp%B2-bond (820 words)

	Sp² bond - Wikipedia, the free encyclopedia
		Notice: For a full understanding of this article, it is important to read and understand the article on orbital hybridization.
		hybridization most commonly occurs in cases where a double bond is going to be formed (as stated above, alkenes are the most frequent example).
		Because hybridized orbitals only create σ bonds a p-type orbital is used for the π bond.
	en.wikipedia.org /wiki/Sp%C2%B2_bond (215 words)

	Carbon
		At normal pressures carbon takes the form of graphite, in which each atom is bonded to three others in a plane composed of fused hexagonal rings, just like those in aromatic hydrocarbons.
		Diamond has the same cubic structure as silicon and germanium and, thanks to the strength of the carbon-carbon bondss, is together with the isoelectronic boron nitride (BN) the hardest substance in terms of resistance to scratching.
		The molecules each contain a triple bond and are fairly polar, resulting in a tendency to bind permanently to hemoglobin molecules, so that the gas is highly poisonous.
	www.sciencedaily.com /encyclopedia/carbon (1840 words)

	Multiple Bonds (Site not responding. Last check: 2007-08-19)
		In addition to this rigidity, the C-C bond length is shorter than that expected for a single bond.
		The linear bond arrangement suggests that the carbon atoms are utilizing sp hybrid orbitals for bonding
		bond with the central N and two orbitals filled with non-bonding pairs of electrons.
	wine1.sb.fsu.edu /chm1045/notes/Geometry/Multiple/Geom06.htm (920 words)

	Carbon nanotube - Wikipedia, the free encyclopedia
		Nanotubes are composed entirely of sp² bonds, similar to graphite.
		bonds found in diamond, this bonding structure provides them with their unique strength.
		While it has long been known that carbon fibers can be produced with a carbon arc, and patents were issued for the process, it was not until 1991 that Sumio Iijima, a researcher with the NEC Laboratory in Tsukuba, Japan, observed that these fibers were hollow.
	en.wikipedia.org /wiki/Carbon_nanotube (2610 words)

	Chapter 9, Section 6 (Site not responding. Last check: 2007-08-19)
		To describe the bonding in benzene in terms of hybrid orbitals, we first choose a hybridization scheme consistent with the geometry of the molecule.
		bonds between an atom and its neighbors is determined by the observed geometry of the molecule.
		bonds are localized in the region between two bonded atoms and do not make a significant contribution to the bonding between any other two atoms.
	cwx.prenhall.com /bookbind/pubbooks/blb/chapter9/medialib/blb0906.html (1599 words)

	The Carbon Implantation in Silicon by Cathodic Arc
		bond ratio is dependent on the kinetic energy of carbon ions.
		bond ratio to increase with the increasing bias, but it may decrease with increasing rate of argon flow.
		bond ratio, and hence the reduction of compressional stress that is the driving force for delaminating the amorphous diamond film from the substrate.
	www.eng.auburn.edu /ADC-FCT2001/ADCFCTabstract/130.htm (373 words)

	PDB: Cruft to Content
		Bonds can only be formed between atoms with the same chain identifier and that are not separated by a TER (chain terminator) record in the PDB file.
		All its bonds, except the one to the closest non-hydrogen atom in the same residue, are deleted.
		Bonds between a pair of terminal atoms are tested against both double and triple bond lengths.
	www.daylight.com /meetings/mug01/Sayle/m4xbondage.html (3567 words)

	Pi Bonds
		The pi bond does not overlap in the region directly between the two carbon atoms where the sigma bond is formed.
		The combination of a sigma and a pi bond between the same two carbon atoms is a double bond.
		These models might lead you to think that double bonds are formed by some kind of process, in which normal single bonds are bent around to form a curved bond, but that is just not true at all.
	dl.clackamas.cc.or.us /ch106-02/pibonds.htm (753 words)

	SMILES Tutorial: Bonds (Site not responding. Last check: 2007-08-19)
		Single, double, triple, and aromatic bonds are represented by the symbols `-', `=', `#', and `:', respectively.
		Ring closure specification is an alternative method for specifying bonds as is explained in the section on ring specification.
		Adjacent aliphatic atoms are assumed to be bonded by a single bond: the single bond symbol `-' is not needed on input.
	www.daylight.com /smiles/smiles-bonds.html (205 words)

	Practice Problems
		This implies a linear geometry with bond angles of 180º.
		The hybridization of the central N atom is sp, this leaves two unhybridized p orbitals that the atom uses to form the two pi bonds that is has.
		Triple bonds also contain two pi bonds and the atoms in triple bonds are sp hybridized.
	antoine.frostburg.edu /chem/simon/chm101/problems10_23key.htm (470 words)

	30
		As with carbon-carbon double bonds, carbon-carbon triple bonds are not free to rotate, but the concept of cis-trans isomers about a triple bond does not make sense.
		This is not the case, the c-c double bonds are all the same length in benzene.
		The pi-bonding electrons (see a picture of the pi-bonding in benzene) in benzene are said to be delocalized and it is this delocalization that gives benzene and related compounds their low chemical reactivity.
	darkwing.uoregon.edu /~ch111/L30.htm (740 words)

	hybridization
		This is largely due to the types of bonds it can form and the number of different elements it can join in bonding.
		Recall that energy is released when bonds form, so it would be to carbon's benefit to try to maximize the number of bonds it can form.
		orbitals forms a bond and the side by side overlap of pure p orbitals forms a pi bond between the carbon atoms.
	www.towson.edu /users/ladon/carbon.html (815 words)

	PPS - Hydrogen Bonds II (Site not responding. Last check: 2007-08-19)
		However, when a residue is buried in the core, hydrogen bonding potential is usually more completely satisfied than for residues on the surface; there are distinct differences between the individual amino acids in this respect.
		In the reduced form it can act as a donor in one hydrogen bond, and as an acceptor in two, although in practice it only appears to be a donor.
		An important resource for studying hydrogen bonding in proteins is the UCL Atlas of Side-Chain and Main-Chain Hydrogen Bonding.
	pps98.man.poznan.pl /ppscore/section7/hbond2.html (550 words)

	Aromatic Hydrocarbons (Site not responding. Last check: 2007-08-19)
		An aromatic hydrocarbon is a cyclic compound where all the atoms in the ring(s) are sp2 having a free "p" orbital to provide a pipeline or "conduit" in which Pi electrons can travel through being distributed throughout the molecule.
		All carbon-carbon bond lengths would be equal and lie between what a single bond between two carbons and a double bond between two carbons would be.
		Because the Nitrogen atom is bonded to two sp2 carbons, its orbitals must also be sp2 in order to have maximum overlap for maximum stability.
	members.aol.com /logan20/aromatic.html (2608 words)

	Multi-atom probes
		The other oxygen of the multi-atom Probe might well be making a strong hydrogen bond to an atom of the Target that was five or more Angstroms away from the grid point.
		Never-the-less all the hydrogen bond and other interaction energies of the whole multi-atom Probe are assigned to the current grid point at each stage of the computation.
		The aromatic ring AR is coplanar with the carboxy group, and might represent the benzene ring of benzoic acid or the heterocyclic ring of nicotinic acid.
	www.moldiscovery.com /docs/grid/c70.html (1741 words)

	Atomic Orbital Theory
		The greater the overlap, the greater is the strength of the bond.
		Pi bonds are considerably weaker than any sigma bond which accounts for the fact that Pi bonds are the first to be broken during a chemical reaction.
		This would mean that the two sp hybrid atoms have a sigma bond (overlap between the sp orbitals) and two Pi bonds (overlap of the p orbitals) or a total of three bonds.
	members.aol.com /profchm/vb.html (2003 words)

	Main Chain
		The ability of the carbonyl group to form two, rather than one, hydrogen bonds, is reflected in only a small number of carbonyl groups that accept both potential hydrogen bonds.
		The two sets of graphs of geometry probably represent mostly the same bonds, as main-chain to main-chain bonds form most (63.2%) of all protein-protein bonds, compared to 10.2% NH to side-chain, and 13.3% side-chain to CO.
		In 47.8% of the main-chain hydrogen bonds, both the NH and the CO are in residues either within or at the ends of alpha-helices.
	www.biochem.ucl.ac.uk /bsm/atlas/mc.html (507 words)

	Valence Bond Theory and Hybrid Atomic Orbitals
		The valence bond (VB) approach is different from the molecular orbital (MO) theory.
		However, the atomic orbitals for bonding may not be "pure" atomic orbitals directly from the solution of the Schrodinger Equation.
		A chemical bond is due to the overlap of atomic orbitals.
	www.science.uwaterloo.ca /~cchieh/cact/c120/hybrid.html (2318 words)

	[No title]
		Terminal bonds (for example, C-H) are excluded as are bonds to terminal groups ending in identical atoms (for example, -CH3, -OH, -CF3).
		Bonds that are in rings are excluded by default, but they can be included.
		If no conformations about a bond will be accepted then the rules applied to that bond are softened by one level.
	dtp.nci.nih.gov /docs/3d_database/chemx/chemx.html (973 words)

	Part I of chapter 1
		Hydbridizations, bond (valence) angles and bond lengths are the three principal factors defining the 3D structure of organic compounds, as they control the size and overall shape of building blocks from which matter is made up.
		(sigma) bonds, and are the strongest covalent bonds known.
		The geometrical consequence of the sp hybridization is the linearity of the structure.
	tigger.uic.edu /~kbruzik/text/chapt1a.htm (900 words)

	covalent bonding - double bonds (Site not responding. Last check: 2007-08-19)
		A double covalent bond is where two pairs of electrons are shared between the atoms rather than just one pair.
		It is important to explore the bonding in ethene in more detail because it has a direct impact on its chemistry.
		An ordinary line represents a bond in the plane of the screen (or the paper if you've printed it), a broken line is a bond going back away from you, and a wedge shows a bond coming out towards you.
	www.chemguide.co.uk /atoms/bonding/doublebonds.html (1004 words)

	United Press International: Superhard electrical crystal carbon film (Site not responding. Last check: 2007-08-19)
		Carbon is an element that can form a wide variety of molecular bonds, included the strongest ones possible -- the so-called "sp3" bonds found in diamonds.
		The diamond bonds derive their strength from carbon atoms exchanging all their free electrons with each other.
		The researchers in Japan created a form of carbon possessing both diamond bonds and weaker, sp2 bonds -- the kind found in the soft, fl graphite used in pencil lead.
	www.upi.com /view.cfm?StoryID=25012002-113344-5543r (517 words)

	Halfway to Diamond (Site not responding. Last check: 2007-08-19)
		Summary: In diamond, carbon forms sp3 bonds in a three-dimensional structure, whereas in graphite, carbon sheets form through sp2 bonds.
		A variety of enigmatic structures between these two have been hinted at when graphite is compressed at ambient temperatures.
		At pressures around 17 gigapascals, half of the weak bonds between the graphite layers convert to diamondlike bonds to create a material hard enough to indent diamond.
	www.comdig.org /print_article.php?id_article=13813 (87 words)

	Graduate Molecular Modeling: Alkenes
		Compare your energies, bond distances, bond angles, and dihedral angles with those in Tables III and IV of the reference.
		Strained double bonds, like those in 1-methyl-trans-cyclooctene and bicyclo[4.3.1]-1-decene, can be either twisted (non-parallel p-orbitals) or folded or both.
		Do MMX calculations on these two structures and on both bridgehead alkenes (double bond in the 5- and in the 7-membered ring) of bicyclo[4.2.1]nonene and on bicyclo[3.3.1]-1-nonene.
	chemistry.gsu.edu /glactone/modeling/Magid/alkenes/alkenes.html (836 words)

	QM(DFT) and MD Studies on Formation Mechanisms of C60 Fullerenes
		The bond length difference is from 0.5 Å to 0.9 Å.
		(l) is the bond strain term, where for n=4m, i=1 is the triple bond and i=2 is the single bonds; for n=4m+2 their bonds are equivalent.
		The key components are the additive energy terms for the dangling bond and the energy cost for bending a triple bond to form a 1,2-benzyne.
	www.foresight.org /Conferences/MNT7/Papers/Cagin2/index.html (2158 words)

	The nature of hydrogen bonding and Density Functional Theory (Site not responding. Last check: 2007-08-19)
		The aim of the proposed workshop is to discuss the nature of hydrogen bonding and the quality of exchange-correlation functionals to describe such interaction.
		Hydrogen bonding (hb) is a prominent interaction in a wide range of materials (biomolecules, liquids, molecular crystals).
		The hydrogen bond interaction (hb) is an attraction between an electronegative atom (donor), and an electron rich atom or region (acceptor) actuated by a hydrogen atom.
	psi-k.dl.ac.uk /data/wp2004_hydrogen.html (983 words)

	Overview of MAKMOPAC (Site not responding. Last check: 2007-08-19)
		MAKMOPAC is an interactive program that generates a Mopac7 input file and determines which of the bonds in the molecule are "rotatable".
		In the definition of rotatable bonds presented above, bonds with partial delocalization are conspicuously absent, since it is up to the user to determine if different orientations about partial double bonds should be considered.
		Once the optimization is complete, the structure should be graphically examined since experience has shown that, depending upon the source of the initial structure, chemical bonds can be broken during the optimization process.
	members.aol.com /btluke/makmop1.htm (668 words)

	The Element Carbon -- Carbon Atom
		bonding with other small atoms, including other carbon atoms, and its small size makes it capable of forming multiple bonds.
		graphite, in which each atom is bonded to three others in a plane composed of fused
		diamond, in which each atom is bonded to four others.
	www.worldofmolecules.com /elements/carbon.htm (1309 words)

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