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Topic: Homolysis

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	Non-ionic Chemical Reactions
		Approximate homolysis temperatures at which half the bonds are cleaved in one hour are also given.
		The covalent bonds that undergo homolysis are colored red, and the unpaired electrons in the resulting radicals are colored pink.
		When a pair of radicals is formed by homolysis, they are briefly held in proximity by the surrounding solvent molecules (the cage).
	www.cem.msu.edu /~reusch/VirtualText/nonionic.htm (4001 words)

	The second step in Fenton-like chemistry in water: calculation of the free energy barrier of O-O homolysis of Fe(III)OOH (Site not responding. Last check: 2007-11-03)
		We have studied this reaction in detail, since it has emerged from our static DFT calculations as one of the most likely second reaction steps, in particular when the hydrolysis of a water ligand is simultaneously taken into account.
		Moreover, the transition state energy is the more important parameter to determine whether the oxygen-oxygen homolysis is indeed a probable mechanism.
		As mentioned before, we expect hydrolysis of water ligands to lower the reaction energy of the oxygen-oxygen homolysis (see the change from 42.6 to 26.1 kcal/mol for reaction I in table 6.1), and secondly we expect hydrolysis to become more frequent for iron(IV) (product) compared to iron(III) (reactant).
	www.cmm.upenn.edu /~ensing/thesis/node47.html (1922 words)

	Department of Chemistry: Seminar (Site not responding. Last check: 2007-11-03)
		Homolysis of singlet allyloxyhydroxycarbene is shown to be a viable pathway, capable of explaining the observed oxperimental results.
		Previous workers have found some theoretical evidence for a transition state in the homolysis of dihydroxycarbene to HOCO and H radicals, but were unable to conclude if such a barrier was real or an artifact of their level of approximation.
		The transition state is rationalized in terms of the electronic states involved in the avoided crossing and by examining the evolution of several atomic and molecular properties during the homolysis using the theory of atoms in molecules.
	www.chemistry.mcmaster.ca /seminars/9900/chem.20000309.html (312 words)

	The determination of thermodynamic and activation parameters for organocobalt bond homolysis
		The line broadening method is particularly useful in determining activation parameters for the dissociation of weakly bonded organometallics where the rate of homolysis exceeds the range measurable by conventional chemical trapping methods.
		Two methods are described and illustrated for the measurement of organo-cobalt bond homolysis energies through reactions of cobalt(II) porphyrins with organic radicals in the presence of olefins.
		The bond homolysis enthalpy for organo-cobalt porphyrin complexes were also determined indirectly by measuring the thermodynamic values for the competition reaction between two organo-cobalt complexes and two olefins in conjunction with a thermochemical cycle.
	repository.upenn.edu /dissertations/AAI9814927 (412 words)

	Homolysis - Wikipedia, the free encyclopedia
		In chemistry, homolysis is chemical bond dissociation of a neutral molecule generating two free radicals.
		Bond cleavage is also possible by a process called heterolysis.
		In biology homolysis means that dividing cell gives two equal-size daughter cells.
	en.wikipedia.org /wiki/Homolysis (123 words)

	POL: ASP: 29th Annual Meeting: Abstracts (Site not responding. Last check: 2007-11-03)
		The quantum yield for bond homolysis in methylcobalamin is determined by the wavelength-dependent partitioning between prompt homolysis and formation of the metastable photoproduct and by the partitioning of the metastable photoproduct between bond homolysis and ground-state recovery.
		The quantum yield for bond homolysis in this case is determined primarily by the competition between geminate recombination and diffusion to form solvent-separated radical pairs.
		The geminate recombination rate is essentially independent of the environment while the diffusion rate is related to the viscosity of the local environment.
	www.kumc.edu /POL/ASP_Home/Meetings/Annual2001/Monday/01abs071.htm (281 words)

	DNA cleavage (Site not responding. Last check: 2007-11-03)
		Since many Cp metal complexes contain or are capable of generating species which cleave, alkylate, or crosslink oligonucleotides, behavior known to constitute the mode of action of many human cancer chemotherapeutic agents, we are developing these compounds as reagents for the modification of DNA.
		We have shown that this complex cleaves DNA in concentration dependent manner at as few as 1.5 molecules/base pair, a surprisingly low ratio considering that the complex does not contain a DNA binding element and that most synthetic enediynes (which generate diradicals) without recognition devices exert this behavior at 100-1000 molecules/base pair.
		This result represents the first demonstration of DNA cleavage by homolysis of a metal-alkyl bond in a Cp-metal complex.
	csma31.csm.jmu.edu /chemistry/Mohler/cleave_dna.htm (335 words)

	The Reaction of the Substrate Analog 2-Ketoglutarate with Adenosylcobalamin-dependent Glutamate Mutase -- Roymoulik et ...
		Recently, we have shown that in glutamate mutase homolysis of the cobalt-carbon bond and hydrogen abstraction from the substrate
		homolysis of AdoCbl, by an estimated 25-30 kcal/mol relative to
		The mechanism by which AdoCbl-dependent enzymes effect homolysis of the coenzyme, a reaction that is highly endothermic in
	www.jbc.org /cgi/content/full/274/17/11619 (2770 words)

	Biophysics
		Reactivity in B12 enzymes involves homolysis (adenosylcobalamin dependent enzymes) or heterolysis (methylcobalamin dependent enzymes) of the active carbon-cobalt bond.
		Although the B12 catalysis is not naturally photoinitiated, a photon can be used to trigger bond homolysis in both enzyme bound and free B12 coenzymes.
		In a second project, related to our studies of cyclohexadiene, femtosecond time-resolved deep ultraviolet spectroscopy is being used to investigate polyene photochemistry.
	www.umich.edu /~sensiong/sension_group_005.htm (310 words)

	IUPAC Gold Book
		The cleavage of a bond ('homolytic cleavage' or 'homolytic fission') so that each of the molecular fragments between which the bond is broken retains one of the bonding electrons.
		A unimolecular reaction involving homolysis of a bond (not forming part of a cyclic structure) in a molecular entity containing an even number of (paired) electrons results in the formation of two radicals:
		Homolysis is also commonly a feature of bimolecular substitution reactions (and of other reactions) involving radicals and molecules.
	goldbook.iupac.org /H02851.html (133 words)

	Can O=NOOH Undergo Homolysis? (Site not responding. Last check: 2007-11-03)
		Given the uncertainty in the Gibbs energy of homolysis, upper and lower rates are 1 × 10
		The recombination of the homolysis products NO and HO is known to lead to mainly peroxynitrous acid.
		If one assumes that a few percent of the recombinations lead to nitrate instead, then the rate of homolysis must be much higher than the rate of isomerization.
	pubs.acs.org /cgi-bin/abstract.cgi/crtoec/1998/11/i02/abs/tx970200x.html (212 words)

	in-cites - An Interview with Professor Willem Koppenol
		I disagreed with him on thermodynamic grounds and we therefore decided to combine our results and try to decide whether peroxynitrite was dangerous by itself, or underwent homolysis to hydroxyl and nitrogen dioxide radicals, or heterolysis to the nitryl cation and hydroxide.
		The conclusion was that homolysis and heterolysis did not take place; furthermore the paper summarized the chemistry of peroxynitrite known at that time.
		As before, we found little evidence that homolysis is a minor pathway.
	www.in-cites.com /papers/ProfWillemKoppenol.html (602 words)

	Materials and methods
		While there can be little doubt about the relevance of the mechanism for enzyme-induced homolysis suggested on the basis of the structure of substrate-free MCM [8], the question remains whether a long axial Co-N bond of the cofactor is also a functional component for this event.
		If inhibitor (or substrate) binding caused bond homolysis via stretching of the axial Co-N bond, we would expect to observe at least some bond elongation also in the inactive enzyme reconstituted with MeCbl (which is less likely to homolyze due to the instability of the formed methyl radical).
		As a result of these observations, preferential binding of the two separated homolysis fragments was suggested as a mechanism for protein-mediated Co-C bond homolysis [7].
	www.uni-graz.at /che3www/strubi/papers/full_text/exafs_glm/paper.htm (7520 words)

	The homolysis of the unique covalent bond between cobalt and C5' of the adenosyl ligand in this fascinating molecule ... (Site not responding. Last check: 2007-11-03)
		The homolysis of the unique covalent bond between cobalt and C5' of the adenosyl ligand in this fascinating molecule leading to a 5'-adenosyl radical and a pentacoordinated CoII atom is the common initial step in the catalytic cycle of all CoB12-dependen
		The homolysis of the unique covalent bond between cobalt and C
		The energy required for this homolysis originates from a conformational change in the protein induced by binding of the substrate.
	www.ncl.ac.uk /tmr.b12/budapest/B12-homo.html (102 words)

	Homolysis (Site not responding. Last check: 2007-11-03)
		In a homolysis the pair of bonding electrons in the bond are equally split between the atoms forming the bond (see Figure 1).
		These generic classifications are also useful given the fact that an Ad 2 reaction may be either a termination or propagation.
		Whilst homolysis (Figure 1) of a bond is the classical method for generating a free radical, it is not the only one.
	www-mitchell.ch.cam.ac.uk /macie/Annotation/homolytic.html (217 words)

	Fenton-like chemistry in water
		For the second step in the reaction mechanism of the Fenton-like reagent, we compare the possibilities of homolysis and heterolysis of the O-O bond and the Fe-O bond of the produced [(H
		We have therefore calculated the free energy barrier for the O-O homolysis of the iron(III)hydroperoxo intermediate in aqueous solution at
		In fact, we predict that with ligands inducing a low-spin iron(III)hydroperoxo intermediate, the barrier for the O-O homolysis will be even significantly lower.
	www.cmm.upenn.edu /~ensing/thesis/node41.html (288 words)

	Untitled Document
		We have been studying the details of this mechanism, as catalyzed by glutamate mutase, as it serves as useful paradigm for how enzymes generate and control free radicals.
		We have shown that the enzyme accelerates homolysis of the coenzyme by a factor of one trillion fold(!), and that furthermore generation of adenosyl radical and removal of hydrogen from the substrate are closely coordinated events.
		Coupling of cobalt-carbon bond homolysis and hydrogen atom abstraction in adenosylcobalamin-dependent glutamate mutase.
	www-personal.umich.edu /~nmarsh/research2.htm (744 words)

	Application Note: Polyolefin Stability
		In the absence of specific reactions, such as elimination retro Diels-Alder, Ene reaction, etc., the initial step in any thermal process is going to be the homolysis of a bond.
		Comparing the energy differences would identify the weakest bond based on a thermodynamic barrier for homolytic bond dissociation: it assumes the energy rises as the atom distance increases from the normal bond distance to asymptotically approach the energy of the separated free radicals in the limit.
		A perfectly regular n-butene/isobutene alternating copolymer has some bonds that are as strong as in polypropylene, but the other bonds, especially with irregularities, in the polybutene make it inherently less stable thermally than even a completely irregular polypropylene by two orders of magnitude.
	www.chamotlabs.com /ApplicationNotes/PolyOlefinStab/PolyStabNote.html (1470 words)

	Dr. Shifa Cheng's Research (Site not responding. Last check: 2007-11-03)
		It was estimated that the half-life for the thermolysis of AdoCbl to an astonishing 1.9 years at 37 °C, in neutral aqueous solution.
		Binding of AdoCbl to AdoCbl-required enzymes in the presence of substrates increases the rate of cobalt-carbon bond homolysis by 9 to 12 orders of magnitude.
		It is believed that conformational distortion of AdoCbl by the bound enzyme is responsible for such tremendous rate acceleration, the so-called "activation" of AdoCbl.
	www.faculty.sfasu.edu /chengs/research.htm (871 words)

	Draft of MOMO Analysis Preprint
		Since none of the free radical reactions can take place until after the bond homolysis step, this initiation reaction is the key to limiting thermal stability.
		Optimizations were continued to a GNORM of 0.1 for accurate energies, and were followed by a FORCE calculation to provide thermodynamic data, and to verify that each geometry was a ground state.
		In order to accurately and realistically simulate bond homolysis in a polymer, it is just as important to use a large enough model compound to reproduce the effect of long range interactions along the polymer chain, as it is to use an accurate method.
	www.chamotlabs.com /ApplicationNotes/MOMOAnalysis/MOMOBDEAnalysis.html (2360 words)

	Amazon.com: "bond homolysis": Key Phrase page (Site not responding. Last check: 2007-11-03)
		See all pages with references to bond homolysis.
		A radical mechanism involving Cr-C bond homolysis was proposed for this reaction.
		The factors influencing catalysis of carbon -cobalt bond homolysis, the question of whether carbon--cobalt bond homolysis and thiyl radical formation are concerted or stepwise, and the issue of whether...
	www.amazon.com /phrase/bond-homolysis (526 words)

	Amazon.com: "thermal homolysis": Key Phrase page (Site not responding. Last check: 2007-11-03)
		between 0 and 100C. Initiation at the required rates under these conditions is confined to compounds with activation energies for thermal homolysis in the range 100-165 kJ/mol.
		The most commonly used peroxide is benzoyl peroxide (1), which undergoes thermal homolysis to form benzoyloxy radicals (reaction 6.1).* The benzoyloxy radicals may undergo a variety of reactions besides adding to monomer, including...
		This compound undergoes thermal homolysis at 60 C to give nitrile-stabilized radicals that abstract the hydrogen atom from Bu3SnH.
	www.amazon.com /phrase/thermal-homolysis (510 words)

	How to draw a free-radical chain mechanism (Site not responding. Last check: 2007-11-03)
		σ-bond homolysis of an initiator such as ROOR or RN=NR to give RO• or R•, respectively, followed by abstraction of H from an X–H bond in a stoichiometric starting material;
		in free-radical polymerizations only, σ-bond homolysis of an initiator, followed by addition of the radical to a C=C bond of a stoichiometric starting material.
		The free radical produced in the last step of the initiation part is the first free radical in the propagation part.
	www.chem.uky.edu /courses/che230/RBG/handouts/freeradchainrules.html (505 words)

	Edwin F. Hilinski - FSU Chemistry and Biochemistry (Site not responding. Last check: 2007-11-03)
		often give fragments formally resulting from bond homolysis and bond heterolysis.
		We are investigating the paths of deactivation from an initially populated pi,pi* excited state leading to the production of radicals and ions.
		McGowan, W. M.; Hilinski, E. F., "Competitive Bond Homolysis and Intersystem Crossing in the Picosecond Time Regime.
	www.chem.fsu.edu /hilinski (562 words)

	Homolysis
		9 letters in word "homolysis": H I L M O O S S Y.
		No anagrams for homolysis found in this word list.
		Words formed from homolysis by changing one letter
	wordnavigator.com /word/homolysis (93 words)

	Amazon.ca: An Introduction to Free Radical Chemistry: Books: Andrew Parsons (Site not responding. Last check: 2007-11-03)
		by Andrew Parsons (Author) "This type of bond cleavage, to give each atom one electron, is known as homolysis or homolytic bond cleavage..." (more)
		This type of bond cleavage, to give each atom one electron, is known as homolysis or homolytic bond cleavage. Read the first page
		Be the first person to review this item.
	www.amazon.ca /Introduction-Free-Radical-Chemistry/dp/0632052929 (320 words)

	Homolysis - Mass Spectrometry Terms
		This is a provisional recommendation for the term Homolysis from the Mass Spectrometry Terms and Definitions Project.
		If you would like to comment on this definition, please contact the Task Group members.
		This page was last modified 15:12, 3 Aug 2006.
	www.msterms.com /wiki/index.php?title=Homolysis (41 words)

	A Simple and Effective Method for Homolysis with a Hypoxanthine-Xanthine Oxidase System and Alteration of Erythrocyte ...
		A Simple and Effective Method for Homolysis with a Hypoxanthine-Xanthine Oxidase System and Alteration of Erythrocyte Phospholipid Composition during the Hemolysis -- TANIGUCHI et al.
		A Simple and Effective Method for Homolysis with a Hypoxanthine-Xanthine Oxidase System and Alteration of Erythrocyte Phospholipid Composition during the Hemolysis
		If you require any further clarification, please contact our Customer Services Department.
	jb.oxfordjournals.org /cgi/content/abstract/89/3/795 (227 words)

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