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Topic: Aromatic ring

Related Topics

Aromatic hydrocarbon

Aromaticity

Benzene ring

Aromatic compound

Hydrocarbon

Aliphatic hydrocarbon

Diene

Benzene

Alkene

Unsaturated hydrocarbon

Pentalene

Alkane

Organic compound

Fuel oil

Alkyne

	Biodegradation of Aromatic Hydrocarbons
		Aromaticity is restored by a dehydrogenase-catalyzed conversion of benzene dihydrodiol to catechol (i.e., 1,2-dihydroxybenzene), which is the ring cleavage substrate.
		and the aromatic substrate (Gibson and Subramanian, 1984).
		Ring cleavage can occur by either of two pathways: the ortho-cleavage pathway, in which the aromatic ring is split between the two carbon atoms bearing hydroxyl groups, or the meta-cleavage pathway, in which the ring is broken between a hydroxylated carbon atom and an adjacent unsubstituted carbon atom (Gottschalk, 1986).
	www.ence.umd.edu /~eseagren/bioAHC97.htm (1299 words)

	aromatic compound - HighBeam Encyclopedia
		aromatic compound any of a large class of compounds that includes benzene and compounds that resemble benzene in certain of their chemical properties.
		For this reason, the bonds in the aromatic ring are less reactive than ordinary double bonds; aromatic compounds tend to undergo ionic substitution (e.g., replacement of a hydrogen bonded to the ring with some other group) rather than addition (which would involve breaking one of the resonant bonds in the ring).
		Presence of the six-membered benzene ring is not essential for aromatic compounds; for example, furan, a heterocyclic compound that has a five-membered ring that includes an oxygen atom, has aromatic properties, as does pyridine, a heterocyclic compound whose six-membered ring includes a nitrogen atom.
	www.encyclopedia.com /doc/1E1-aromatic.html (469 words)

	Aromaticity at AllExperts
		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.
		Secondly, he is describing electrophilic aromatic substitution proceeding (thirdly) through a Wheland intermediate, in which (fourthly) the conjugation of the ring is broken.
		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.
	en.allexperts.com /e/a/ar/aromaticity.htm (1497 words)

	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)

	Aromatic Hydrocarbons
		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.
		In discussing electrophilic aromatic substitutions on Benzene, it was apparent that all six carbon atoms were equivalent in their ability to be the center of the substitution since the electron density exhibited by the Pi electron system was evenly distributed over the entire ring.
		To understand this you have to think of a ring that is deactivated,but a ring which the relative electron density is greater at the ortho and para positions due to the resonance effect of the lone pairs.
	members.aol.com /logan20/aromatic.html (2608 words)

	Aromatic Reactivity
		The benzylic hydrogens of alkyl substituents on a benzene ring are activated toward free radical attack, as noted earlier.
		Compounds in which two or more benzene rings are fused together were described in an earlier section, and they present interesting insights into aromaticity and reactivity.
		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)

	Aromatic hydrocarbon Summary
		Derived chiefly from petroleum and coal tar, aromatic hydrocarbons tend to be reactive.
		Although benzoin and benzoic acid had been called aromatics before 1820, it was not until the 1850s that benzene and its derivatives were placed in the chemical family of aromatics.
		The so-called aromatic spices and resins such as frankincense, camphor, turpentine, were shown in the 1880s not to be chemically similar to benzene, but rather to be derivatives of a family of ten-carbon compounds, called terpenes.
	www.bookrags.com /Aromatic_hydrocarbon (759 words)

	Process for producing bromo-aromatic condensed ring compound - Patent 6528692
		In the present invention, the aromatic condensed ring compound means a condensed polycyclic hydrocarbon in the form with the greatest number of non-neighboring double bonds or a heterocyclic compound in which one or more carbon atoms constituting said condensed polycyclic hydrocarbon are replaced by hetero atom(s).
		Examples of the aromatic condensed ring compound in which the number of carbon atom constituting the aromatic condensed ring is 15 or more include pyrene, naphthacene, triphenylene, chrysene, picene, perylene, pentaphene, pentacene, hexaphene, hexacene, coronene, trinaphthylene, heptaphene, heptacene, pyranthrene, ovalene, aceanthrylene, acephenanthrylene, pleiadene, tetraphenylene, rubicene, coronene, phenanthridine and the like.
		The benzene condensed ring compound herein includes compounds in which the condensed polycyclic hydrocarbons in the form with the greatest number of non-neighboring double bonds are constituted by benzene rings only.
	www.freepatentsonline.com /6528692.html (2095 words)

	Aromatic Hydrocarbon 6 Jar
		The bezene ring is a cyclic hydrocarbon of C H. At each corner of the hexagon there is assumed to be a carbon atom.
		The bezene ring is a cyclic hydrocarbon of C H. At each corner of the hexagon there is cheap assumed to be a carbon atom.
		The bezene ring is a cyclic hydrocarbon of C H. discount At each corner of the hexagon there is assumed to be a carbon atom.
	www.dnmfilms.com /aromatic-hydrocarbon-6-ring.htm (406 words)

	IR: aromatics (Site not responding. Last check: 2007-09-08)
		Not only do these bands distinguish aromatics, but they can be useful if you want to determine the number and positions of substituents on the aromatic ring.
		In some instances, it is useful to remember that aromatics in general show a lot more bands than compounds that do not contain an aromatic ring.
		If you are presented with two spectra and told that one is aromatic and one is not, a quick glance at the sheer multitude of bands in one of the spectra can tell you that it is the aromatic compound.
	orgchem.colorado.edu /hndbksupport/irtutor/aromaticsir.html (338 words)

	Composition for the assay of albumin - Patent 5194390
		Furthermore, heterocyclic aromatic ring systems, including fused ring systems, wherein the heteroatom of the aromatic ring system includes one or more nitrogen, oxygen or sulfur atoms, or mixtures thereof, can be utilized in the method and composition of the present invention.
		The benzene, or phenyl, ring is preferred because of its abundance, cost, and, especially, because of the ease of introducing a variety of electron-withdrawing functionalities onto the phenyl ring.
		It is envisioned that any aromatic or quasi-aromatic moiety, capable of having electron-withdrawing substituents present on the aromatic or quasi-aromatic ring, and possessing sufficient aromaticity to distribute the negative charge of an anionic conjugate base throughout the aromatic or quasi-aromatic moiety can be used in accordance with the present invention.
	www.freepatentsonline.com /5194390.html (5951 words)

	nbm21
		As in the chain compounds, a parallel classification divides the ring compounds into families characterized by the nature of the negative components: hydrocarbons, alcohols, amines, etc. The normal cyclic hydrocarbon, a cyclane, or cycloparaffin, is a simple ring of CH neutral groups.
		In the aromatic ring this limitation is removed, and compounds with three or four of the highly reactive nitro groups in the six-member ring are common.
		As previously mentioned, a ring with even one CH group deviates substantially from the typical aromatic behavior, and any such ring is classified with the cyclic structures, but this effect is confined to the specific ring, and any adjacent aromatic rings retain their aromatic character.
	www.reciprocalsystem.com /nbm/nbm21.htm (6207 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)

	heteroaromatic : aromatic molecules containing 1 atom other than C in the aromatic ring
		All aromatic rings with one 6 membered ring are given the base name benzene.
		Aromatic compounds tend to react in a manner that retains aromaticity.
		Aromatic nitro compounds are used in the synthesis of dyes, and a series of nitrations are used to make TNT.
	www.ipfw.edu /chem/256/256Spring05/256nt0512.htm (888 words)

	Aromaticity - Wikipedia, the free encyclopedia
		Whereas benzene is aromatic (6 electrons, from 3 double bonds), cyclobutadiene is not, since the number of π delocalized electron is 4, which of course is a multiple of 4.
		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).
		Aromatic properties are tested to the limit in a class of compounds called cyclophanes.
	en.wikipedia.org /wiki/Aromatic (1602 words)

	The MSDS HyperGlossary: Aromatic
		A prototypical aromatic compound is benzene, so a layperson might prefer to think of an aromatic compound as something that has a ring structure like that of benzene, C
		The term "aromatic" was used by chemists to describe certain chemicals with peculiar odors long before anyone understood what atoms were or how they might be connected to form molecules.
		When the term aromatic is used in an MSDS it is referring to the chemical definition of aromaticity, not the smell or odor of the compound.
	www.ilpi.com /msds/ref/aromatic.html (676 words)

	Aromaticity
		Special magnetic properties are observed when an aromatic species is placed in a magnetic field.
		These properties are the result of a strong "ring current" that is produced in the π
		ring are shielded and the regions around the periphery of the ring are deshielded.
	chem.stthomas.edu /pages/Ippoliti/aromaticity.html (132 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)

	Aromatics
		When interpreting the spectrum of an aromatic compound, remember to count the number of protons in the aromatic region to determine how many times the ring is substituted.
		If an aromatic ring has more than one substituent, careful analysis of the shifts and splitting pattern of the protons in the aromatic region reveals the positions on the ring of the different substituents.
		If you are interested in learning details about aromatic splitting and shifts, consult either your TA or one of the references listed in the reference section.
	orgchem.colorado.edu /hndbksupport/specttutor/arom.html (417 words)

	ALICYCLIC, ALICYCLIC-FUSED AND AROMATIC-FUSED RING LACTONES (JECFA 52, 2004)
		All 16 lactones in the group of aliphatic, alicyclic-fused and aromatic-fused ring lactones used as flavouring agents are expected to be readily absorbed from the gastrointestinal tract, metabolized and excreted, predominantly in the urine.
		Alternatively, oxidation of ring substituents or the ring itself yields polar polyhydroxylated carboxylic acid metabolites that may be excreted primarily in the urine.
		On the basis of these data, it was concluded that the metabolic options available to lactones fused to aromatic rings include excretion as the glycine or glutamine conjugates of the open-chain hydroxycarboxylic acid derivative, or oxidation or reduction of the side-chain and subsequent excretion as the glucuronic acid conjugate.
	www.inchem.org /documents/jecfa/jecmono/v52je13.htm (13519 words)

	Möbius and Hückel Spiro-aromatic Systems
		The latter example comprises what we term a spiroaromatic ring system, in which two aromatic rings are fused by sharing a single atom rather than by a mutual bond.
		As before, the cyclophosphazene ring B is non aromatic, whereas the phosphabenzene ring B is clearly aromatic.
		The NICS values imply that the aromaticity is in fact localised to each ring, and does not follow coractate rules, with the obvious caveat that measuring NICS values at individual ring centroids may not be an appropriate measure of overall coarctate aromaticity.
	www.ch.ic.ac.uk /rzepa/spiro (1736 words)

	Chapter 12 Conjugation and Aromaticity
		Aromatic compounds have the characteristic of being unusually stable and undergoing different reactions from nonconjugated and conjugated alkenes.
		The extensive delocalization predicted by the resonance forms explains the structure of benzene and also its increased stability relative to acyclic conjugated compounds such as 1,3,5-hexatriene.
		Experimental evidence has shown that molecules that are considered aromatic have the following characteristics in common.
	www.ipfw.edu /chem/262/262spring03/262nt0307.htm (404 words)

	Iodination Of Aromatic Jar
		Keywords aromatic oxidative iodination iodoarenes aromatic hypervalent iodine compounds dichloroiodo It can be either an aldehyde or a ketone and may or may not contain an aromatic ring.
		Keywords aromatic oxidative iodination iodoarenes aromatic hypervalent iodine compounds dichloroiodo formed by opening of the aromatic ring remain elusive to detection.
		Keywords aromatic oxidative iodination iodoarenes aromatic hypervalent iodine compounds dichloroiodo formed by opening of the aromatic ring jar remain elusive to detection.
	www.dubbdesigns.com /iodination-of-aromatic-ring.htm (621 words)

	Chemblog (Site not responding. Last check: 2007-09-08)
		By convention, the double-headed arrow indicates that the two structures are simply hypothetical, since neither is an accurate representation of the actual compound.
		Aromatics with two half-twists corresponding to the paradromic topologies first suggested by Johann Listing have been proposed by Rzepa in
		In carbo-benzene the ring bonds are extended with alkyne and allene groups.
	chemblog.chemicalblogs.com /33_chemblog/archive/51_aromaticity.html (1461 words)

	Hydrocarbons derivatives of cyclohexane or of a cyclohexene, having a side-chain containing an acyclic ...
		In this group, in condensed ring systems of six-membered aromatic rings and other rings, the double bond belonging to a benzene ring is not considered as unsaturated for the non-aromatic ring condensed thereon, e.g.
		the 1,2,3,4-tetrahydro- naphthalene ring is considered to be saturated outside the aromatic ring.
		In this group, in condensed ring systems of six-membered aromatic rings and other rings, the double bond belonging to the benzene ring is not considered as unsaturated for the non-aromatic ring condensed thereon.
	www.wipo.int /ibis/ipc7en/c07c.xml?mg=C07C04300 (2739 words)

	The aromaticity of Pericyclic reaction transition states
		Of course, aromatic molecules can support chiral groups as substituents on the rings, but we exclude this class in our argument here, since we are concerned only with the nature of the aromatic structures themselves.
		For relatively small sized rings (<14), aromaticity can be related to the degree of alternation in the bond lengths; no alternation indicates a high degree of aromaticity (and implied stability), whereas partitioning into short (double) and long (single) bond lengths indicates no aromaticity, or even anti-aromaticity.
		The stereochemistry at the bicyclic ring junction in E had been left undefined in the question, in the hope of provoking the students (and the present author!) to think about the implications.
	www.ch.ic.ac.uk /rzepa/pericyclic (3688 words)

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