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Topic: Simple aromatic ring

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	Reference.com/Encyclopedia/Simple aromatic ring
		Simple aromatic rings, also known as simple arenes or simple aromatics, are aromatic organic compounds that consist only of a conjugated planar ring system with delocalized pi electron clouds.
		In the basic aromatic rings the lone pair of electrons is not part of the aromatic system and extends in the plane of the ring.
		In the oxygen (O) and sulfur (S) containing aromatic rings one of the electron pairs of the heteroatoms contributes to the aromatic system (similar to the non-basic nitrogen containing rings), while the second lone pair extends in the plane of the ring (similar to the basic nitrogen containing rings).
	www.reference.com /browse/wiki/Simple_aromatic_ring (410 words)

	Simple aromatic ring - Wikipedia, the free encyclopedia
		Simple aromatic rings are aromatic organic compounds (also known as arenes or aromatics) that consist only of conjugated planar ring systems with delocalized pi electron clouds instead of discrete alternating single and double bonds.
		Typical simple aromatic compounds are benzene and indole.
		In the oxygen (O) and sulfur (S) containing aromatic rings one of the electron pairs of the heteroatoms contributes to the aromatic system (similar to the non-basic nitrogen containing rings), while the second lone pair extends in the plane of the ring (similar to the basic nitrogen containing rings).
	en.wikipedia.org /wiki/Simple_aromatic_ring (379 words)

	Spartanburg SC \| GoUpstate.com \| Spartanburg Herald-Journal
		Aromaticity is a chemical property in which a conjugated ring of unsaturated bonds, lone pairs, or empty orbitals exhibit a stabilization stronger than would be expected by the stabilization of conjugation alone.
		Aromatic molecules are also able to interact with each other in an "edge-to-face" orientation: the slight positive charge of the substituents on the ring atoms of one molecule are attracted to the slight negative charge of the aromatic system on another molecule.
		Aromaticity is found in ions as well: the cyclopropenyl cation (2e system), the cyclopentadienyl anion (6e system), the tropylium ion (6e) and the cyclooctatetraene dianion (10e).
	www.goupstate.com /apps/pbcs.dll/section?category=NEWS&template=wiki&text=aromaticity (1828 words)

	H. Nomenclature of Aromatic Heterocycles
		This means that when a molecule has multiple functional groups including hydroxyls, double bonds and triple bonds, you pick the longest continuous chain containing the alcohol or alcohol groups and you number the chain so that the alcohol groups have the lowest positions possible.
		Simple aldehydes and ketones are named similarly to alcohols.
		Given its high prority the ring is named as a cycloalkanecarbaldehyde.
	www.brynmawr.edu /Acads/Chem/mnerzsto/SpringNomenclature3.htm (742 words)

	AROMATIC SUBSTITUTED SECONDARY ALCOHOLS, KETONES, AND RELATED ESTERS (JECFA Food Additives Series 48)
		The aromatic secondary alcohols (and aromatic ketones after reduction to the corresponding secondary alcohols) are then either conjugated with glucuronic acid and excreted primarily in the urine or are further oxidized and excreted mainly as glycine conjugates.
		As aromatic esters are generally hydrolysed in vivo by the catalytic activity of carboxylesterases, which predominate in hepatocytes, it is anticipated that the 10 esters in the group of 38 flavouring agents will be hydrolysed to their parent aromatic or aliphatic alcohols and carboxylic acids.
		Generally, the aromatic secondary alcohols (and aromatic ketones after reduction to the corresponding secondary alcohols) are conjugated with glucuronic acid and excreted in the urine, or the alcohols and ketones are further oxidized and conjugated primarily with glycine to form hippuric and phenaceturic acids and excreted.
	www.inchem.org /documents/jecfa/jecmono/v48je13.htm (8129 words)

	Reference.com/Encyclopedia/Aromatic hydrocarbon
		An aromatic hydrocarbon (abbreviated as AH) or arene is a hydrocarbon, the molecular structure of which incorporates one or more planar sets of six carbon atoms that are connected by delocalised electrons numbering the same as if they consisted of alternating single and double covalent bonds.
		Examples of non-benzene compounds with aromatic properties are furan, a heterocyclic compound with a five-membered ring which includes an oxygen atom, and pyridine, a heterocyclic compound with a six-membered ring containing one nitrogen atom.
		Aromatization of cyclohexanes and other aliphatic rings: reagents are, catalysts used in hydrogenation such as platinum, palladium and nickel (reverse hydrogenation), quinones and the elements sulfur and selenium.
	www.reference.com /browse/wiki/Aromatic_hydrocarbon (721 words)

	Naming aromatic compounds
		This is a simple example of a halogen attached to the benzene ring.
		Whenever you draw a benzene ring with one other thing attached to it, you are in fact drawing a phenyl group.
		There is a -COOH group attached to the ring and, because the name is based on benzoic acid, that group is assigned the number 1 position.
	www.chemguide.co.uk /basicorg/conventions/names3.html (1352 words)

	Benzene Information Center - benzene exposure legal
		The aromatic products of the reaction are then separated from the reaction mixture by extraction with any one of a number of solvents, including diethylene glycol or sulfolane, and benzene is then separated from the other aromatics by distillation.
		Electrophilic aromatic substitution is a general method of substituting aromatic rings such benzene cleanup as benzene.
		The reaction is the acylation of an aromatic ring (such as benzene) with an acyl chloride using a strong Lewis acid catalyst.
	www.scipeeps.com /Sci-Chemistry_Topics_Ap_-_B/Benzene.html (2035 words)

	Preparation of polypyrroles, and films obtained by this method - Patent 4569734
		The aromatic sulfonic acids or salts of these which are employed according to the invention as conductive salts can be derived from a very large variety of monoaromatic or polyaromatic compounds, and can contain one or more sulfonic acid groups, depending on the parent aromatic structure.
		The aromatic parent compound of the aromatic sulfonic acids, or of their salts, which are used according to the invention can be, in particular, benzene, fused aromatic systems, e.g.
		Aromatic sulfonic acids, or salts of these, which are preferably used as conductive salts in the novel process are those which are derived from benzene, naphthalene, anthracene, phenanthrene, polystyrene having a number average mean molecular weight of from 500 to 20,000, naphthoquinone or anthraquinone.
	www.freepatentsonline.com /4569734.html (2683 words)

	Aromatic Reactivity
		The activation or deactivation of the ring can be predicted more or less by the sum of the individual effects of these substituents.
		The benzylic hydrogens of alkyl substituents on a benzene ring are activated toward free radical attack, as noted earlier.
		This two-step mechanism is characterized by initial addition of the nucleophile (hydroxide ion or water) to the aromatic ring, followed by loss of a halide anion from the negatively charged intermediate.
	www.cem.msu.edu /~reusch/VirtualText/benzrx2.htm (2321 words)

	Nomenclature
		Aromatic compounds are what we call compounds derived from benzene.
		In this system, one of the groups that is attached to the benzene ring is considered to be attached to the number one carbon atom.
		Notice that there are three nitro groups attached; and since it is the nitrogen atom that is attached to the ring, the NO group in the upper left corner is written in the opposite direction just to emphasize that it is the nitrogen atom that is attached to the ring.
	dl.clackamas.cc.or.us /ch106-02/nomencla3.htm (721 words)

	Chemistry : Chapter 12 : Overview (Site not responding. Last check: 2007-10-10)
		Aromatics have a resonance structure, where the double bonds are shifted one ring position.
		Since the true structure is a mixture of all resonance structures, aromatics actually have a double-bond ring within the single-bonded ring and the ring geometry is planar.
		To see the difference in geometry, the ring form of the monosaccharide is oriented so that the ether (which is part of the ring) is in the back and the CH OH group is oriented in the back and on top of the ring.
	www.wwnorton.com /chemistry/overview/ch12.htm (1894 words)

	Aromatic Reactivity
		This activation or deactivation of the benzene ring toward electrophilic substitution may be correlated with the electron donating or electron withdrawing influence of the substituents, as measured by molecular dipole moments.
		If the atom bonded to the ring has one or more non-bonding valence shell electron pairs, as do nitrogen, oxygen and the halogens, electrons may flow into the aromatic ring by p-π conjugation (resonance), as in the middle diagram.
		Clearly, the alkyl substituents activate the benzene ring in the nitration reaction, and the chlorine and ester substituents deactivate the ring.
	www.cem.msu.edu /~reusch/VirtualText/benzrx1.htm (2788 words)

	MEDCHEM (Site not responding. Last check: 2007-10-10)
		Aromaticity, as defined by Huckels rule and other physical chemical features, is an important group in medicinal chemistry - the presence of an aromatic group almost dominating the field of bioactive substances.
		Although the structures of aromatic rings is drawn with alternating single and double bonds, the net electron density occurring between two carbon atoms of a benzene is more of a hybrid between a single and double bond -> therefore the positions on a benzene ring are equal energy (degenerate) when unsubstituted.
		The simple, unsubstituted arenes are lipophilic and the addition of a benzene ring to an existing drug structure adds greatly to its partition coefficient properties.
	www2.umt.edu /medchem/teaching/421lect3.htm (1724 words)

	Botany online: Ions and Small Molecules - Aromatic Hydrocarbons
		Ring systems with double bonds that cannot be localized are called mesomere systems.
		Heterocyclic rings are components of nucleotides that have an important role in the cell.
		Rings with five or six elements are most stable and thus most common.
	www.biologie.uni-hamburg.de /b-online/e16/16i.htm (400 words)

	Media Portfolio
		Every (carbon) atom in the ring path in benzene contributes a p atomic orbital to develop the pi molecular orbital system which resides above and below the plane of the atoms in the ring.
		Since these rings are bent out of planarity by the shape of the molecule, the double bonds in the six-membered rings do not mix their pi electrons to form an aromatic system, and buckminsterfullerene shows chemical reactivity characteristic of alkenes rather than aromatic compounds.
		Electrophilic aromatic addition yields products which are less stable than reactants because aromaticity is lost, whereas electrophilic aromatic substitution preserves aromaticity and yields products having stabilities comparable to those of reactants.
	wps.prenhall.com /wps/media/objects/724/741576/chapter_15.html (793 words)

	PerlMol - Chemistry::Ring - Represent a ring as a substructure of a molecule
		Returs a vector with the centroid, defined as the average of the coordinates of all the atoms in the ring.
		Naively guess whether ring is aromatic from the molecular graph, with a method based on Hückel's rule.
		It also adds the 'ring/rings' attribute to the molecule and to all ring atoms and bonds; this attribute is an array reference containing the list of rings that involve that atom or bond (or all the rings in the case of the molecule).
	www.perlmol.org /pod/Chemistry/Ring.html (364 words)

	Daylight Theory: Molecules and Reactions in a Computer
		The concept of aromaticity in the Daylight system is not a chemical one, but rather is a set of rules designed for a chemical nomenclature system (this is discussed more in the SMILES chapter).
		Ring detection: Discovering those atoms and bonds that are part of ring systems.
		Note that the definition of aromaticity is not intended to imply anything about the reactivity, magnetic resonance spectra, heat of formation, or odor of substances.
	www.daylight.com /dayhtml/doc/theory/theory.mol.html (1716 words)

	VSS Technology Library - Compositionally Controlled Bitumen for Quality
		These ring systems may be associated with napthenic (saturated) ring systems and they both may have attachments of various branched and linear hydrocarbons.
		The aromatic portion is mostly naptho-aromatic hydrocarbons with three or four napthenic rings per molecule.
		The resins consist of mainly polycylic molecules containing saturated aromatic and hetero-aromatic rings and hetero atoms in various functional groups, the resins are not as polar as the asphaltenes and hence are not as interactive (11).
	www.slurry.com /techpapers/techpapers_contrbit.shtml (3286 words)

	C&EN: SCIENCE & TECHNOLOGY - DECIPHERING METAL ANTIAROMATICITY
		A chemical system is aromatic if it sustains an induced ring current that leads to a diamagnetic shift--a decrease in the magnetic susceptibility of the compound.
		For antiaromatic compounds, the shift in ring current is in the opposite direction, referred to as a paramagnetic shift.
		In this orbital, bonding occurs between the Al atoms on the short sides of the ring, while the region between the Al atoms on the long sides is antibonding.
	pubs.acs.org /cen/science/8150/8150sci1.html (3097 words)

	OSHA TECHNICAL MANUAL - SECTION IV: CHAPTER 2
		Relatively simple crude oil assays are used to classify crude oils as paraffinic, naphthenic, aromatic, or mixed.
		All aromatics have at least one benzene ring (a single-ring compound characterized by three double bonds alternating with three single bonds between six carbon atoms) as part of their molecular structure.
		Severe lube hydrotreating, at temperatures in the 600°-750° F range and hydrogen pressures up to 3,000 psi, is capable of saturating aromatic rings, along with sulfur and nitrogen removal, to impart specific properties not achieved at mild conditions.
	www.osha.gov /dts/osta/otm/otm_iv/otm_iv_2.html (10392 words)

	CDK Request for Comments #7
		I propose that aromaticity is generally coded by setting a CDKConstants.ISAROMATIC flag both in the aromatic ring atoms as well as in the aromatic ring bonds.
		Aromatic ring systems are not only detected by classes like org.openscience.cdk.aromaticity.HueckelAromaticityDetector, but they may also be created by parsing SMILES strings.
		In the latter case, no alternating single/double bond pattern is given, but the ring atom symbols are either written in lower case letters or the bond symbols indicate an "aromatic" bond.
	cdk.sourceforge.net /old_web/rfc7.html (199 words)

	Benzene Summary
		Benzene is the simplest of the aromatic hydrocarbons.
		Benzene's hexagonal ring structure is of considerable importance because it is the basis for most of the class of chemicals known as aromatic compounds.
		The reaction involves the acylation of benzene (or many other aromatic rings) with an acyl chloride using a strong Lewis acid catalyst such as aluminium chloride..
	www.bookrags.com /Benzene (3351 words)

	Spectroscopy Problems
		The peaks in the aromatic region strongly suggest 1,4-disubstitution, and there is a peak at 117 which would be consistent with a nitrile carbon.
		The proton NMR also shows evidence for 1,4-disubstitution on an aromatic ring and an isolated methyl with a chemical shift which is consistent with direct attachment to the ring.
		The simplest structure which is consistent with all of these data would be an aromatic compound with a nitrile and a methyl group, 1,4 to each other on the ring.
	www.chem.uic.edu /web1/ocol/spec/P7.htm (470 words)

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