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Topic: Alkyne


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  The Organometallic HyperTextBook: Alkyne Complexes
The bonding of an alkyne (acetylene) to a transition metal complex is similar to that of an alkene complex.
Alkynes tend to be more electropositive and therefore tend to bind more tightly to a transition metal than alkenes.
A number of transition metal alkyne complexes are intermediates in the cyclotrimerization of alkynes to substituted benzenes.
www.ilpi.com /organomet/alkyne.html   (759 words)

  
  Alkyne - Wikipedia, the free encyclopedia
Alkynes are generally prepared by dehydrohalogenation of vicinal alkyl dihalides or the reaction of metal acetylides with primary alkyl halides.
scrambling of alkynes in alkyne metathesis to new alkyne compounds
[2+2+1]cycloaddition of an alkyne, alkene and carbon monoxide in the Pauson–Khand reaction
en.wikipedia.org /wiki/Alkyne   (634 words)

  
 alkyne. The Columbia Encyclopedia, Sixth Edition. 2001-05
In the International Union of Pure and Applied Chemistry (IUPAC) system of chemical nomenclature, the name of an alkyne is derived from the name of the corresponding alkane by replacing the -ane alkane suffix with -yne and, if necessary, adding a prefix to indicate the location of the triple bond in the molecule.
The alkynes are sometimes referred to as the acetylene series, the higher members of the series being named as derivatives of acetylene, e.g., propyne as methylacetylene, 1-butyne as ethylacetylene, and 2-butyne as dimethylacetylene.
The usefulness of the alkynes in chemical synthesis is due both to the reactions of the triple bond itself and to the relative acidity of a hydrogen atom bonded to a triply bonded carbon.
www.bartleby.com /65/al/alkyne.html   (269 words)

  
 Alkynes   (Site not responding. Last check: 2007-10-22)
The alkynes are the third homologous series of organic compounds of hydrogen and carbon, where there is at least one triple-bond between the atoms in the molecules.
Alkynes are compounds which have low polarity, and have physical properties that are essentially the same as those of the alkanes and alkenes.
The carbon-carbon triple bond of the alkynes is formed in the same way as a double bond of the alkenes, by the elimination of atoms or groups from two adjacent carbons.
www.ucc.ie /ucc/depts/chem/dolchem/html/dict/alkynes.html   (1641 words)

  
 C&EN: LATEST NEWS - SILICON COMPLETES TRIPLE CROWN
And during the past 30 years, clever synthetic strategies have led to alkene and alkyne analogs of all the heavier group 14 elements from silicon to lead--with the exception of a compound containing a silicon-silicon triple bond.
West's group, which prepared the first compound with a silicon-silicon double bond in 1981, was part of a new wave in chemistry that eventually led to the synthesis of doubly bonded compounds for most of the elements in groups 13 to 16.
Alkyne analogs of germanium, tin, and lead were finally reported in 2000 and 2002 by chemistry professor Philip P. Power and coworkers of the University of California, Davis.
pubs.acs.org /cen/news/8238/8238notw1.html   (550 words)

  
 Alkynes: Reactions
The addition of halogen acids to alkynes is a stepwise process which generally involves a solvent-equilibrated carbocation intermediate.
Alkynes can also be partially reduced to trans-alkenes using a "dissolving metal reduction", in which the alkyne is formed by a radical mechanism in the presence of Li or Na metal dissolving in liquid ammonia.
Terminal alkynes are slightly acidic and a powerful base such as sodium amide (sodium previously dissolved in liquid ammonia) will react with these compounds to give alkyne anions, which are powerful nucleophiles.
www.chem.uic.edu /web1/OCOL-II/WIN/ALKENE/92/ALKYNE.HTM   (940 words)

  
 Alkyne Summary
The alkynes are traditionally known as acetylenes, although the name acetylene is also used to refer specifically to the simplest member of the series, known officially as ethyne.
Alkynes are generally prepared by dehydrohalogenation of vicinal alkyl dihalides or the reaction of metal acetylides with primary alkyl halides.
Alkyne • Amide ;• Amine ;• Azo compound • Benzene derivative • Carboxylic acid • Cyanate ;• Ester ;• Ether ;• Haloalkane ;• Imine ;• Isocyanide ;• Isocyanate ;• Ketone ;• Nitrile ;• Nitro compound • Nitroso compound • Peroxide ;• Phosphoric acid • Pyridine derivative • Sulfone ;• Sulfonic acid • Sulfoxide ;• Thioether ;• Thiol ;• Toluene derivative
www.bookrags.com /Alkyne   (1118 words)

  
 Alkyne metathesis - Wikipedia, the free encyclopedia
is an organic reaction involving the redistribution of alkyne chemical bonds.
This organometallic alkyne then undergoes a metathesis reaction with neoheptyne to the final product.
Alkyne metathesis is extensively used in ring closing operations and RCAM stands for ring closing alkyne metathesis.
en.wikipedia.org /wiki/Alkyne_metathesis   (474 words)

  
 Alkyne Metathesis in Synthesis: Syntheses of (+)-Ferrugine and Anatoxin-a
Although much emphasis has been placed on the importance of alkene metathesis in organic synthesis, alkyne metathesis is also significant.
Metathesis reactions of alkynes with alkenes and metathesis reactions of alkynes with alkynes have both been carried out efficiently.
An enantiospecific synthesis of the potent anti-Alzheimer's agent (+)-ferruginine 1 and two enantiospecific syntheses of the potent anti-Alzheimer's agent anatoxin-α 2 were submitted essentially simultaneously earlier this year.
www.organic-chemistry.org /Highlights/2004/25OctoberB.shtm   (276 words)

  
 Alkynes
Alkynes are hydrocarbons that have at least one triple co-valent bond between two adjacent carbons.
Alkynes are similar to alkenes in that the triple bond is between two carbon atoms that have undergone sp hybridization using one 2s and one 2p atomic orbital to produce two sp hybrid orbitals.
Hydrogen atoms can be added to an alkyne on a one mole to one mole ratio to get an alkene where the Hydrogen atoms have been added on the same side of the molecule.
members.aol.com /logan20/alkynes.html   (1389 words)

  
 Practice Quiz - Hydration of an Alkyne
The H will always go to the carbon with fewer substituents; since a terminal alkyne has one carbon attached to a H and one attached to a carbon, the H will always go to the carbon at the end (attached to an H).
In internal alkynes, the addition will give two products, since the H can add equally favorably to either side of the carbon-carbon triple bond since each is bonded to a carbon.
The 0.051 moles of alkyne make it present in the least amount of the two reactants and it is therefore the limiting reagent.
orgchem.colorado.edu /labquizzes/hydalkyne/hydalkyneans.html   (560 words)

  
 alkyne on Encyclopedia.com
ALKYNE [alkyne], any of a group of aliphatic hydrocarbons whose molecules contain one or more carbon-carbon triple bonds (see chemical bond).
In the International Union of Pure and Applied Chemistry (IUPAC) system of chemical nomenclature, the name of an alkyne is derived from the name of the corresponding alkane by replacing the - ane alkane suffix with - yne and, if necessary, adding a prefix to indicate the location of the triple bond in the molecule.
The IUPAC name of the simplest alkyne, HC[triple bond]CH, is thus ethyne, which is derived from ethane.
www.encyclopedia.com /html/a1/alkyne.asp   (326 words)

  
 Help   (Site not responding. Last check: 2007-10-22)
The molecule shown has 2 degrees of unsaturation, there is no E,Z stereochemistry and is neither an alkene nor an alkyne.
The molecule shown has 2 degrees of unsaturation, the methyl groups are cis (Z), and is not an alkene nor an alkyne.
The molecule shown has 3 degrees of unsaturation, the cyano and ethyl groups are cis (Z), and the molecule is neither an alkene nor an alkyne.
www.chem.uic.edu /web1/ocol/Q2/Q2-3h.htm   (336 words)

  
 Media Portfolio
A terminal alkyne is at the end of a chain and has increased reactivity because the acetylenic hydrogen is acidic.
The reaction is used as a qualitative test for the presence of terminal alkynes or as a way to separate terminal alkynes from internal alkynes.
Both substrates, the hydrogen and the alkyne, have to be adsorbed on the catalyst for the reaction to occur.
wps.prenhall.com /wps/media/objects/340/348272/wade_ch09.html   (1355 words)

  
 Alkyne: Facts and details from Encyclopedia Topic   (Site not responding. Last check: 2007-10-22)
The diels-alder reaction is an organic chemical reaction (specifically, a cycloaddition) between a conjugated diene and a substituted alkene (commonly...
An alkene is one of the three classes of unsaturated hydrocarbons that contain at least one carbon-carbon double bond and have the general molecular...
An aldehyde is either a functional group consisting of a terminal carbonyl group, or a compound containing a terminal carbonyl group....
www.absoluteastronomy.com /encyclopedia/a/al/alkyne.htm   (925 words)

  
 Alkyne - Search Results - ninemsn Encarta
The members of the alkyne series contain a triple bond between two carbon atoms in the molecule.
They are very active chemically and are not found...
Chemistry, Organic : Classification and Nomenclature : Alkenes and Alkynes
au.encarta.msn.com /Alkyne.html   (105 words)

  
 Master of Orion III - The Official Web Site - Cool Stuff
He stomped toward Alkyne, his fiery orange eyes locked in a deep scowl that was firmly directed at the young engineer, who instinctively shifted a step backwards.
Alkyne could not respond to that either, so he resumed his study of the approaching shuttle.
Alkyne was studying her intently, and then caught himself, embarrassed.
moo3.quicksilver.com /cool/contest/hg.html   (1106 words)

  
 Alkyne Molecule Geometry
Alkynes, containing a carbon-carbon triple bond, have the linear or straight geometry as a primary feature.
Ethyne or acetylene, HC=CH, is the simplest alkyne example.
Since a triple bond is present and each carbon is attached to 2 atoms (1 H and 1 C), the geometry is linear.
www.elmhurst.edu /~chm/vchembook/209alkynes.html   (240 words)

  
 nov19
First we learn about alkynes and their reactions, then we learn how to design a synthesis.
alkyne is less reactive than an alkene, but an alkyne is more reactive than a halo-substituted alkene, because of the electron-withdrawing effects of the halogen.
Acid catalyzed addition to an internal alkyne results in an enol that rearranges to a ketone.
spot.pcc.edu /~chandy/241/nov19.html   (298 words)

  
 Mechanistic Investigation of Stoichiometric Alkyne Insertion into Pt-B Bonds and Related Chemistry Bearing on the ...
The stoichiometric results exclude simple, bimolecular insertion of an alkyne into Pt-B bonds of 1, and the observed dependence on phosphine and alkyne strongly favors a mechanism where phosphine dissociation generates a three-coordinate intermediate that mediates alkyne insertion.
The rates of alkyne diborylation are also sensitive to the nature of the alkyne as 4-octyne reacts much more readily than diphenylacetylene.
Thus, the data are consistent with a catalytic manifold that is identical to that observed in the stoichiometric reaction.
pubs.acs.org /cgi-bin/abstract.cgi/orgnd7/1996/15/i24/abs/om960123l.html   (419 words)

  
 Welcome to the Stryker Research Group
Schwiebert, K. E.; Stryker, J. "Transition metal-mediated [3+2+2] allyl alkyne cycloaddition reactions - a new reactivity pattern for the synthesis of 7-membered carbocycles" J.
Casty, G. L.; Stryker, J. "Radical additions to a coordinated hydrocarbyl ligand - synthesis of titanacyclobutane complexes via regioselective free-radical addition to a Ti(III) allyl complex" J.
H5)OTf - facile conversion to alkyne metallacyclobutane complexes by nucleophilic-addition" Organometallics, 1993, 12, 600-602.
www.chem.ualberta.ca /~stryker/Pages/pubs.html   (1293 words)

  
 Dalton Transactions Articles
A dimolybdenum complex with an alkyne ligand parallel to the metal—metal bond: synthesis, structure and cluster formation reactions of [Mo Ph
substituents are both directed away from the alkyne ligand in a syn arrangement, creating a plane of symmetry, whereas in unsymmetrical 2b they are presumed to occupy an anti arrangement.
Extended-Hückel molecular orbital calculations show that the alkyne orientation in 2 results in better overlap between the alkyne and metal orbitals, as well as reduced repulsive interactions with the bridging thiolate ligands.
www.rsc.org /Publishing/Journals/DT/article.asp?doi=b103698j   (213 words)

  
 Student Doctor Network Forums - OC Question...Alkyne Reduction   (Site not responding. Last check: 2007-10-22)
I know that is you reduce an alkyne with Na and NH3, the result is a trans-alkene.
Kaplan flashcards say that the reduction of an alkyne on a metal surface (Pd) results in an alkane.
Schaum's states that the reduction of an alkyne with Lindlar's catalyst (H2/Pd) results in a cis-alkene.
forums.studentdoctor.net /showthread.php?t=174146   (1024 words)

  
 Alkyne -   (Site not responding. Last check: 2007-10-22)
The CC bond distance with 121 picometers is also much less than that of the alkene bond which is 134 pm or the alkane bond with 153 pm.
Unlike alkanes, alkynes are unstable and very reactive.
hydroboration reaction of alkynes with organoboranes to vinylic boranes
psychcentral.com /psypsych/Alkyne   (679 words)

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