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	Annulene - Wikipedia, the free encyclopedia
		They are named as [ n ]annulene, where n is the number of carbon atoms in their ring.
		The first three annulenes are cyclobutadiene, benzene, and cyclooctatetraene (respectively [4], [6], and [8]annulene).
		Annulenes may be aromatic ([6]annulene), non-aromatic ([8]annulene), or anti-aromatic ([4]annulene).
	en.wikipedia.org /wiki/Annulene (91 words)

	Ch 11 : Annulenes
		Annulenes are the family of completely conjugated, monocyclic hydrocarbons.
		The annulenes are named as [n]-annulene where n is an even number that represents the number of C atoms in the ring.
		Higher members of the annulene series have also been synthesised and investigated in relation their aromaticity.
	www.chem.ucalgary.ca /courses/351/Carey5th/Ch11/ch11-7-2.html (177 words)

	Annulene Guides, Tutorials (Site not responding. Last check: 2007-11-06)
		They are named as [ n ]-annulene, where n is the number of carbon atom s in their ring.
		The first three annulenes are cyclobutadiene, benzene, and cyclooctatetraene (respectively [4]-, [6]-, and [8]-annulene).
		They are named as n -annulene, where n is the number of carbon atoms in their ring.
	www.masterliness.com /a/Annulene.htm (126 words)

	[18]ANNULENE
		These can be separated by chromatography on alumina coated with 20% silver nitrate, but this is unnecessary for the synthesis of [18]annulene, since all three substances give this annulene on catalytic hydrogenation.
		The presently described procedure for the synthesis of [18]annulene, although the overall yield is low by the standard normally set for Organic Syntheses, illustrates the above general route leading to the theoretically important macrocyclic annulenes, and in this way [14]-, [16]-, [18]-, [20]-, [22]-, and [24]annulenes have been prepared in pure crystalline form.
		The compound is of considerable interest, since it is the type of annulene that was predicted to be aromatic by Hückel.
	www.orgsyn.org /orgsyn/orgsyn/prepContent.asp?prep=cv6p0068 (2773 words)

	A Mobius 16 pi-Electron System (Site not responding. Last check: 2007-11-06)
		In 1964 E. Heilbronner predicted that large annulenes incorporating a 180 ° twist of the pi-electron band would be destabilized in the 4n+2 electron case, but stabilized if occupied by 4n electrons.
		A Möbius annulene will necessarily be larger than benzene in order to accomodate the ring twist while maintaining a reasonable overlap of the p-orbitals.
		However, the sixteen carbon annulene depicted here is unlikely to adopt the twisted conformation shown above, since many other less energetic configurations and conformations are readily assumed.
	www.cem.msu.edu /~reusch/VirtualText/mobius.htm (299 words)

	Counting electrons in Pericyclic Reaction Mechanisms
		In benzene ([6] annulene) the two predominant Kekule structures are known as resonance isomers, and the actual geometry of the molecule is approximately the mean of the two.
		Much of the ambiguity of the [16] annulene reaction occured because being a Huckel 4n electron system, its planar form was formally anti-aromatic.
		The original report of the reactions of [16] annulene was by G. Schroder, W. Martin and J. Oth, Angew Chemie, 1967, 79, 861.
	www.ch.ic.ac.uk /local/organic/tutorial/rzepa2 (1018 words)

	18annulene
		This plausible prediction came from weighing the known high energetic costs for a molecule to adopt sub-van der Waals contacts and extended angles against what at that time was a more vague estimation of the aromatic stabilization energy.
		Baumann and Haddon had proposed early on that dynamical electron correlation would be needed to handle the higher annulene structures, but the computational effort was not expended.
		Higher order annulenes, such as [18]annulene, are finally managable by hybrid RHF/density functional ab initio computations.
	www.sdsc.edu /~kimb/heme/html/18annulene.dec.96.html (1237 words)

	[No title] (Site not responding. Last check: 2007-11-06)
		The general name annulene is sometimes given to rings that contain alternating single and double bonds in a single Lewis structure.
		The ten-membered ring of this bridged [10]annulene is planar enough that it exhibits some aromatic character.
		The blue Hs appear at 9 delta in its NMR spectrum, whereas the red Hs appear at the high field position of -3 delta.
	www.du.edu /~jhornbac/organic/annulene.html (257 words)

	UvA DARE
		Relative Intramolecular Reactivity of the Insulated p Double Bond and the 14p Annulene Perimeter toward Sulfur Trioxide in the Sulfonation of Isopyrenes
		annulenes ; sulfur trioxide ; sultones ; carbyl sulfates ; isopyrene
		The sulfonation of isopyrene (1) and its 5-methyl- and 5,10-dimethyl derivative 2 and 3 with SO3 in both dichloromethane and nitromethane as solvent has been studied.
	dare.uva.nl /record/24784 (165 words)

	Timothy D. Lash
		The versatility of this tetrapyrrolic system stems in part from its intrinsic stability and its ability to form chelates with many different transition metals at varying oxidation levels.
		Porphyrins also represent an unparalleled family of aromatic macrocycles that formally possess [18]annulene characteristics and as such are the only naturally occurring examples of higher bridged annulene structures.
		Although the porphyrin system is generally near planar, it can be severely distorted from planarity without significantly sacrificing its aromatic properties.
	www.che.ilstu.edu /people/faculty/lash.htm (535 words)

	Aromatic Hydrocarbons
		Aromatic annulenes are monocyclic compounds where all the Pi electrons are conjugated.
		Not all annulenes are aromatic.[12] Annulene and [16] annulene are examples of non-aromatics because they have the wrong number of Pi electrons, 12 and 16.
		The resonance stabilized conjugated structure of Benzene was first proposed by Kekule who, legend has it, had a dream vision of snakes chasing their tails around a circle.
	members.aol.com /logan20/aromatic.html (2609 words)

	Chemistry Question:
		That type of bond alternation is the atypical morphology of annulenes.
		The reasons for this will not be discussed, but there is a simple rule to deduce an annulenes stabillity.
		Each annulene has its own peculiarities and are interesting on there own.
	www.chemicalforums.com /index.php?op=articles;id=19 (536 words)

	World Intellectual Property Organization (Site not responding. Last check: 2007-11-06)
		9S)-12-hexyl-5, 6,7, 8,9, 10-hexahydro-6, 9- (epiminomethano) benzo [a] [8] annulene; (6R, 9S)-12-nonyl-5, 6,7, 8,9, 10-hexahydro-6, 9- (epiminomethano) benzo [a] [8] annulene; (6R,
		6,7, 8,9, 10-hexahydro-6, 9- (epiminomethano) benzo [a] [8] annulene; (6R, 9S)-12-ethyl-5, 6,7, 8,9, 10-hexahydro-6, 9- (epiminomethano) benzo [a] [8] annulene;
		6,7, 8,9, 10-hexahydro-6, 9- (epiminomethano) benzo [a] [8] annulene ; (6R, 9S)-12- (4, 4,4-trifluorobutyl)-5, 6,7, 8,9, 10-hexahydro-6, 9- (epiminomethano) benzo [a] [8] annulene ; or the pharmaceutically acceptable salts or stereoisomers thereof.
	www.wipo.int /ipdl/IPDL-CIMAGES/view/pct/getbykey5?KEY=03/86395.031023&ELEMENT_SET=DECL (5175 words)

	Möbius and Hückel Molecular Orbitals arising from C=C=C components in Annulene rings
		Summary: Following our previous suggestion that C=C=C units can induce Möbius characteristics in cyclic annulenes, we present a more detailed analysis of the molecular orbitals generated by the interaction of such units with the p orbitals the annulene.
		His suggestion that this might occur with conformationally flexible annulenes has recently been confirmed with the identification of several Möbius-like conformations of [16]annulene, for which Nucleus Independent Chemical Shift (NICS) calculations have indicated mildly aromatic behaviour.
		The inclusion of one or more C=C=C units into a cyclic annulene can result in chiral molecules which have a two or higher-fold axis of symmetry and some measure of Möbius characteristics.
	www.rsc.org /suppdata/P2/B0/B003971N/b003971n.html (3075 words)

	Questions dealing with aromatic systems (Site not responding. Last check: 2007-11-06)
		NMR spectroscopy showed that all of the hydrogen atoms were equivalent.
		The name annulene refers to monocyclic compounds having alternating single and double bonds.
		Benzene is thus [6]annulene as the number in brackets gives the ring size.
	www.ualberta.ca /~eblackbu/chem161/aromat1.html (100 words)

	Ring Systems
		In systematic nomenclature an annulene with seven or more carbon atoms may be named [n]annulene, where n is the number of carbon atoms.
		Carbenes, derived by formal insertion of a divalent carbon atom into an even-membered annulene.
		Benzene derivatives having para positions (or meta) bridged by a chain (commonly 10 to 12 atoms long) (Latin ansa, handle).
	www.chem.qmw.ac.uk /iupac/class/rings.html (1566 words)

	mitchell.htm (Site not responding. Last check: 2007-11-06)
		Mitchell, R. H.; Khalifa, N. A.; Dingle, T. Synthesis of the first large annulene fused to cyclopentadienide.
		Determination of the effective bond localizing ability ("relative aromaticity") and diamagnetic anisotropy of several organometallic moieties, J.
		Mitchell, R. H., Lau, D. K., Mak, T. W., Wu, B., Anklin, C. Synthesis of the first [n]paracyclophane with an annulene as the aromatic, a necklace-like molecule; NMR, X-ray and MMX structural comparisons, Can.
	www.chemistry.uvic.ca /mitchell/mitchell.htm (1005 words)

	AROMATICITY — Chapter 9
		Completely conjugated monocyclic polyenes, [n] annulene, where n = no. of C
		[12] annulene — unstable and has paramagnetic (opposite with aromatic groups) ring current
		[18] annulene — aromatic and not strained (planarity)
	www.chem.uab.edu /advincula/chapt9.htm (281 words)

	Supplemental data
		The Aromaticity and Möbius Characteristics of Carbenohetero-[8] and Triplet State Annulenes
		Summary: Two types of annulene which may show significant Möbius aromatic character and bond and twist delocalisation are proposed; triplet states with 4n+2 occupancy of the p
		RCIS(triplets,root=1) route used for positively charged systems, which exhibit pathologic SCF convergence problems at the ROHF and ROB3LYP levels.
	www.rsc.org /suppdata/CC/B1/B110626K/b110626k.html (274 words)

	World Intellectual Property Organization (Site not responding. Last check: 2007-11-06)
		3-benzodioxol-5-ylmethyl) -5,6, 7,8, 9,10-hexahydro-6, 9- (epiminomethano) benzo [a] [8] annulene; (6R,
		6,7, 8,9, 10-hexahydro-6, 9- (epiminomethano) benzo [a] [8] annulene; or a pharmaceutically acceptable salt or stereoisomer thereof.
		6,7, 8,9, 10-hexahydro-6, 9-(epiminomethano) benzo [a] [8] annulene; (6S, 9R,11S)-11-phenyl-5, 6,7, 8, 9,10-hexahydro-6, 9- (epiminomethano) benzo [a] [8] annulene;
	www.wipo.int /ipdl/IPDL-CIMAGES/view/pct/getbykey5?KEY=03/86314.031023&ELEMENT_SET=DECL (6372 words)

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