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Computational chemical studies on thermochemistry and ring strains in cyclic [ n ]Metaphenyleneacetylenes, butadiyne-bridged [4n] Metacyclophynes, and butadiyne-bridged [4n]paracyclophynes
Published in
2010
PMID: 20695635
Volume: 75
   
Issue: 17
Pages: 5797 - 5809
Abstract
The thermochemical properties and ring strains in cyclic [n]metaphenyleneacetylenes ([n]CMPAs), butadiyne-bridged [4n] metacyclophynes (B-B[4n]MCs), and butadiyne-bridged [4 n]paracyclophynes (B-B[4n]PCs) were studied using a homodesmotic reaction scheme coupled with density functional theory (B3LYP/6-31G, mPW1PW91/6-31G, and M06-2X/6-31+G//B3LYP/6-31G). Strain energies of [n]CMPAs and B-B[4n]MCs decrease first from very high values for small rings to become zero when n becomes 6, then increase with n, and finally decrease as n becomes larger than 8. In the case of B-B[4n]PCs, strain energies decrease with increasing n. Heats of formation of [n]CMPAs, B-B[4n]MCs, and B-B[4n]PCs increase steadily with increasing numbers of phenylacetylene and 1-(buta-1,3-diynyl)benzene to reach a near-constant value per unit monomer as n increases. The geometries and (vibrational and nuclear magnetic resonance) spectroscopic properties of [n]CMPAs, B-B[4n]MCs, and B-B[4n]PCs were also studied. Geometrical parameters, Raman frequencies, and 1H NMR chemical shifts of [3]CMPA and [4]CMPA are found to be in good agreement with compounds for which there are experimentally available values at the B3LYP/6-31G* level of theory. In addition, electronic structure calculations were carried out for [n]CMPAs, B-B[4n]MCs, and B-B[4n]PCs. Ring diameters were also calculated for B-B[4n]PCs. © 2010 American Chemical Society.
About the journal
JournalJournal of Organic Chemistry
ISSN00223263
Open AccessNo
Concepts (46)
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    B3LYP/6-31G
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    Butadiyne
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    Electronic structure calculations
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    Geometrical parameters
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    Heats of formation
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    HOMODESMOTIC REACTIONS
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    Nmr chemical shifts
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    Per unit
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    Phenylacetylenes
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    RAMAN FREQUENCIES
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    RING DIAMETER
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    RING STRAINS
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    SMALL RINGS
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    SPECTROSCOPIC PROPERTY
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    THERMOCHEMICAL PROPERTIES
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    Acetylene
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    Aromatic hydrocarbons
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    Benzene
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    CHEMICAL COMPOUNDS
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    Electronic structure
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    Geometry
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    Nuclear magnetic resonance
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    Organic polymers
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    Raman spectroscopy
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    Resonance
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    Strain
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    Strain energy
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    Thermochemistry
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    Density functional theory
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    Acetylene derivative
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    Benzene derivative
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    Cyclophane derivative
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    Phenylacetylene
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    Article
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    Chemical structure
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    Controlled study
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    Heat
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    Proton nuclear magnetic resonance
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    Raman spectrometry
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    Thermodynamics
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    Vibration
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    Alkynes
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    Benzene derivatives
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    Computer simulation
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    Molecular structure
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    Stereoisomerism