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Topic: Isomer

	Testing the physics of nuclear isomers
		An isomer is a long-lived excited state of an atom's nucleus--a state in which decay back to the nuclear ground state is inhibited.
		A nuclear isomer is an atom whose nucleus is in a higher energy state than its ground state.
		The long lifetime results because transition to the ground state would require a large change either in the spatial structure of the atom's nucleus (for a shape isomer) or in the angular momentum (a measure of the spin of the nucleus) between the isomer and the nuclear ground state (for a spin isomer).
	www.eurekalert.org /features/doe/2005-08/drnl-ttp082205.php (961 words)

	isomer. The Columbia Encyclopedia, Sixth Edition. 2001-05
		Isomers are classified as structural isomers, which have the same number of atoms of each element and molecular weight but different bonding patterns (see chemical bond), or as stereoisomers, which have the same number of atoms of each element, molecular weight, and bonding pattern but in which the atoms have different spatial relationships.
		Tautomers are structural isomers that readily convert from one isomeric form to another and therefore exist in equilibrium.
		Position isomers have similar chemical properties since they differ only in the location of the functional group (e.g., the OH in an alcohol or the double bond in an alkene).
	www.bartleby.com /65/is/isomer.html (952 words)

	Isomer Summary
		Position isomerism occurs because not all hydrogen atoms in a molecule are identical.
		Isomers that rotate the plane of polarization to the right are dextrorotory isomers, those that rotate to the left are laevorotory isomers.
		Isomerism was first noticed in 1827, when Friedrich Woehler prepared cyanic acid and noted that although its elemental composition was identical to fulminic acid (prepared by Justus von Liebig the previous year), its properties were quite different.
	www.bookrags.com /Isomer (2558 words)

	ISU Weed Science Online - Resolved Isomers
		Isomers are compounds that have the same chemical formula, but the elements of the molecules are arranged slightly differently.
		In some situations the inactive isomer may not contribute to the performance of the herbicide, whereas in others in may simply have a lower level of activity than the active isomer.
		By marketing the active isomer, less chemical is needed (an envirnomental benefit) and this may allow the manufacturer to reduce the cost of the product or allow increased performance of the product.
	www.weeds.iastate.edu /mgmt/qtr00-1/isomers.htm (627 words)

	Spartanburg SC \| GoUpstate.com \| Spartanburg Herald-Journal (Site not responding. Last check: 2007-10-11)
		In chemistry, isomers are molecules with the same chemical formula and often with the same kinds of bonds between atoms, but in which the atoms are arranged differently (a bit like a chemical anagram).
		This group includes chain isomerism whereby hydrocarbon chains have variable amounts of branching; position isomerism which deals with the position of a functional group on a chain; and functional group isomerism in which one functional group is split up into different ones.
		There are also isotopomers or isotopic isomers that have the same numbers of each type of isotopic substitution but in chemically different positions.
	www.goupstate.com /apps/pbcs.dll/section?category=NEWS&template=wiki&text=isomer (849 words)

	Carbohydrates - Isomers (Site not responding. Last check: 2007-10-11)
		Glyceraldehyde, the simplest carbohydrate, exhibits properties of a chiral or optical isomer compound.
		Glyceraldehyde can exist in two isomeric forms that are mirror images of each other which are shown in the graphic on the left.
		Chemists have used this configuration of D-glyceraldehyde to determine the optical isomer families of the rest of the carbohydrates.
	www.elmhurst.edu /~chm/vchembook/542isomers.html (304 words)

	Proposed Rule 2006 - Schedules of Definition of "Positional Isomer'' as It Pertains to the Control of Schedule I ...
		The terms "optical isomer'' and "geometric isomer'' are specific scientific terms and it is easy to determine whether one substance is an optical or geometric isomer of another.
		The terms "optical isomer'' and "geometric isomer'' are specifically defined and well understood scientific terms, and it is easy to determine whether one substance is an optical or geometric isomer of another.
		The addition of a definition for the term "positional isomer'' as it applies to 21 CFR 1308.11(d) will assist legitimate research and industry in determining the control status of substances that are isomers of Schedule I hallucinogens.
	www.deadiversion.usdoj.gov /fed_regs/rules/2006/fr0525.htm (2481 words)

	Isomers of Coordination Complexes (Site not responding. Last check: 2007-10-11)
		Coordination isomers vary according to which anions are coordinated to the metal (inner sphere) and which are acting as counterions to the complex ion (outer sphere)
		Linkage isomers contain the same ligands but one or more of the ligands are coordinated to the metal through a different atoms.
		In this case, the spatial orientation of ligands is such that the two isomers are non-super imposable mirror images of one another.
	webhost.bridgew.edu /shaefner/general/isomers_131.html (220 words)

	ES&T Online News: More clues to HBCD isomer mystery
		They discovered that the relative abundance of the isomers in the environment is often very different than the composition of the commercial product, which is added to polystyrene foams in insulation and upholstered furniture.
		The γ isomer comprises 70–90% of the HBCD formulation, says Mehran Alaee, a research scientist with the Aquatic Ecosystem Protection Research Branch of the National Water Research Institute, which is part of Environment Canada.
		In contrast, the α isomer did not appear to be metabolized; researchers familiar with the study agree that this finding provides strong evidence for why the α isomer is so much more likely to bioaccumulate.
	pubs.acs.org /subscribe/journals/esthag-w/2005/mar/science/kb_hbcd.html (1148 words)

	Scary Things Come in Small Packages (washingtonpost.com)
		The isomer bomb began its roller-coaster ride from a controversial experiment in a relatively unknown science center to the inner sanctum of the military -- the E-Ring of the Pentagon.
		The "I believe in isomers" campaign hit him just as he prepared to take over his new job in Foggy Bottom as chief scientist of the Arms Control and Disarmament Agency, whose mission was to both promote arms control and be on the lookout for new developments in weapons.
		The isomer bomb is foolish, Zimmerman said, but it's foolish in a dangerous sort of way if it pushes other countries to build real nuclear weapons in the hope of deterring the United States from using a fanciful hafnium bomb.
	www.washingtonpost.com /ac2/wp-dyn?pagename=article&contentId=A22099-2004Mar24¬Found=true (7063 words)

	Columbia Encyclopedia- isomer - AOL Research & Learn
		Among their different properties, ethanol has a boiling point of 78.5°C and a freezing point of -117°C; dimethyl ether has a boiling point of -25°C and a freezing point of -138°C. Ethanol and dimethyl ether are isomers because they differ in the way the atoms are joined together in their molecules:;g340;none;1;g340;;;block;;;;no;1;71808n;206902n;;;;;isomer340;;;left;stack;;;;;
		In isobutane, CH3CH(CH3)2, the carbon atoms are joined in a branched chain; the isobutane molecule can be visualized as a carbon atom bonded to one hydrogen atom and to three methyl (CH3) groups.
		For example, there are two geometric isomers of 2-butene, CH3CH⊇CHCH3:;g340A;none;1;g340A;;;block;;;;no;1;139392n;56775n;;;;;isomer340a;;;left;stack;;;;;The prefix cis- means same side and trans- means opposite side; they are used when the groups on either side of the double bond are identical or closely related, e.g., methyl and ethyl.
	reference.aol.com /columbia/_a/isomer/20051206061609990002 (948 words)

	Isomer
		Isomers are molecules or molecular compounds that are similar in that they have the same molecular formula, however have different arrangements of the atoms or groups of atoms (functional groups) involved.
		If you were to construct models of them, they would not be able to be super imposed on each other in the same way that your right and left hand can not be superimposed on each other.
		These types of isomers were found in many cases to affect plane-polarized light by rotating it either to the right or left and hence termed optically active molecules, and it is for this reason that they are called optical isomers.
	www.monashscientific.com.au /Isomer.htm (497 words)

	Physics Today May 2004 - Search and Discovery: Conflicting Results on a Long-Lived Nuclear Isomer of Hafnium Have Wider ...
		Nuclear isomers are excited states that eventually decay to the ground state, mostly by gamma radiation.
		The Hf state is an example of a so-called K isomer.
		Assuming that half the Hf in the working target is isomeric, that L-shell photoionization is maximal, and that one ionization in 600 triggers an isomer decay, it would cost, on average, 16 MeV of x-ray energy to recover 2.45 MeV in gamma rays.
	www.physicstoday.org /vol-57/iss-5/p21.html (2285 words)

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