scholarly journals Studies on lactone stabilities

1969 ◽  
Author(s):  
Θεμιστοκλής Παπαδέλλης
Keyword(s):  
Hydroxybutyric Acid ◽  
Polycyclic Compounds ◽  
Ring Strain ◽  
Effect Of Solvent ◽  
Acid Lactone ◽  
Heats Of Combustion ◽  
Organic Solutions ◽  
Cis And Trans ◽  
Modified Theory ◽  
Good Agreement

The theories of Bucourt concerning the stabilities of mono-and polycyclic compounds have been critically exarnined and modified. Ring strain (as measured by heats of combustion in the literature) may be calculated with irnproved accuracy by the modified theory. The theory has been further tested by a deterrnination of the stabilities (relative to the hydroxy-acids) in SO mole % aqueous tetrahydrofuran of the series of mono- and polycyclic 8 -lactones: y. y, 8 -trirnethyl- 8 - valerolactone, ~ and trans - 1-oxadecal-2-one, cis- and trans - 1-oxa-l0-methyldecal-Z-one, 6a-.!.-butyl-l-oxa-9a, 10 (3 -decal-Z-one, 6a -t-butyl-l-oxa-9(3, 10(3 -decal-Z-o~e, 4-oxa-5 U -estran-3-one, 4-oxa-SU-cholestan-3-one, and 4-oxa-S{3 -cholestan-3-one. Good agreement was found between experimental and ca1culated values, when account was taken of a hitherto unrecognized deformation of the cyc10hexane ring caused by bulky equatorial substituents. The effect of solvent composition on the equilibrium between y -hydroxybutyric acid and y -butyrolactone was studied using the solvents 0-80 mole % aqueous tetrahydrofuran, dioxane, acetone and dimethylsulfoxide. Minima and maxima of the ratio hydroxy-acid/lactone were observed as the water content decreased from 100%; the ratio at the minima and maxima decreased with rising temperature. Thermodynamic parameters have been calculated and explained in terms of an extension of current theories of the structure of aqueous organic solutions.

Nuclear magnetic resonance studies. XIV. Conformational equilibria of α-halocyclohexanones

1967 ◽  
Vol 45 (23) ◽  
pp. 2943-2953 ◽  
Author(s):  
Yuh-Hsu Pan ◽  
J. B. Stothers
Keyword(s):  
Equilibrium Constants ◽  
Dipolar Interactions ◽  
Proton Spectroscopy ◽  
Solvent Interactions ◽  
Reaction Field ◽  
Conformational Equilibria ◽  
Classical Models ◽  
Acetonitrile Solutions ◽  
Cis And Trans ◽  
Good Agreement

The conformational equilibria of α-fluoro-, α-chloro-, and α-bromo-cyclohexanone have been examined by proton spectroscopy in cyclohexane, carbon tetrachloride, benzene, chloroform, p-dioxane, and acetonitrile solutions over a range of concentrations. The cis- and trans-4-t-butyl derivatives were used as reference compounds for the two chair conformations. Equilibrium constants were estimated from the α-proton spectral data in two ways and compared with the results obtained by a variety of methods. Consistently good agreement was found between our results and those available from dipole moment measurements. This study is the most extensive investigation of the α-halocyclohexanone equilibria to date. Calculations using simple classical models for steric, electrostatic, and induced dipolar interactions were found to predict the observed trends. The solvent effects on the axial and equatorial α-proton shieldings in the "fixed" systems are discussed in terms of solute–solute and (or) solute–solvent interactions, and evidence for reaction field contributions is presented.

Solid-State C-13 NMR Studies of Vulcanized Elastomers X. N-t-Butyl-2-Benzothiazole Sulfenamide Accelerated Sulfur Vulcanization of cis-Polyisoprene at 75.5 MHz

1992 ◽  
Vol 65 (2) ◽  
pp. 427-443 ◽  
Author(s):  
M. R. Krejsa ◽  
J. L. Koenig
Keyword(s):  
Solid State ◽  
Solid State Nmr ◽  
Chain Scission ◽  
Sulfur Concentration ◽  
Nmr Studies ◽  
Double Bond Migration ◽  
Sulfur Vulcanization ◽  
Equilibrium Swelling ◽  
Cis And Trans ◽  
Good Agreement

Abstract Accelerated sulfur vulcanized cis-polyisoprene was analyzed using C-13 solid-state NMR to determine the chemical microstructure of the network. Three formulations were analyzed consisting of varying accelerator/sulfur ratios. All formulations yielded similar network structures, but the amount of sulfurization varied with sulfur concentration. At low percent cure, only polysulfidic A-type cis-structures were found. For longer cure times, the A-type structures shortened to monosulfldic, and B-type polysulfidic structures, both cis and trans, were formed. The amount of trans-sulfurized product was constant with cure once this resonance appeared. No isomerization, chain scission, saturation, or double bond migration was detected. The NMR measurements appeared to show fairly good agreement with equilibrium swelling measurements.

Darstellung und Schwingungsspektren von cis- und trans-[OsXY(acac)2], X ≠ Y = Cl, Br, I sowie Normalkoordinatenanalyse von trans-[OsClBr(acac)2]/Synthesis and Vibrational Spectra of cis- and trans-[OsXY(acac)2], X ≠ Y = Cl, Br, I, and Normal Coordinate Analysis of trans-[OsClBr(acac)2]

1998 ◽  
Vol 53 (2) ◽  
pp. 227-231
Author(s):  
K. Dallmann ◽  
W. Preetz
Keyword(s):  
Normal Coordinate Analysis ◽  
Force Constants ◽  
Vibrational Modes ◽  
Normal Coordinate ◽  
Valence Force ◽  
Valence Force Field ◽  
Stretching Vibrations ◽  
Cis And Trans ◽  
Ir And Raman ◽  
Good Agreement

Abstract In the reaction of K2[OsX3 Y3] with boiling water/acetylacetone (1:1) the six mixed com­plexes cis-and trans-[OsX2 (acac)2] (X ≠ Y = Cl, Br, I) are formed, which have been purified by column chromatography with toluene on silica gel. The IR and Raman spectra (10K) show the intraligand vibrations of the acac groups with nearly constant frequencies and the stretching vibrations of OsO in the range 460-696, of OsCl at 315-345, of OsBr at 210-225, and of Osl at 160-175 cm-1 . A normal coordinate analysis based on a modified valence force field was performed for trans-[OsClBr(acac)2] and the vibrational modes have been assigned. With a set of 32 force constants, taking into account the intraligand vibrations, a good agreement between observed and calculated frequencies has been achieved. The valence force constants are fd (OsCl•) = 1.75, fd(OsBr′) = 1.63 and fd (OsO) = 3.27 mdyn/Å.

scholarly journals Applying MOG to Lensing: Einstein Rings, Abell 520 and the Bullet Cluster

Galaxies ◽  
2018 ◽  
Vol 6 (2) ◽  
pp. 43 ◽  
Author(s):  
John Moffat ◽  
Sohrab Rahvar ◽  
Viktor Toth
Keyword(s):  
Gravitational Lensing ◽  
Equations Of Motion ◽  
Astronomical Observations ◽  
Test Particles ◽  
Strong Lensing ◽  
Modified Theory Of Gravity ◽  
Small Set ◽  
Modified Theory ◽  
Bending Of Light ◽  
Good Agreement

We investigate gravitational lensing in the context of the MOG modified theory of gravity. Using a formulation of the theory with no adjustable or fitted parameters, we present the MOG equations of motion for slow, nonrelativistic test particles and for ultrarelativistic test particles, such as rays of light. We demonstrate how the MOG prediction for the bending of light can be applied to astronomical observations. Our investigation first focuses on a small set of strong lensing observations where the properties of the lensing objects are found to be consistent with the predictions of the theory. We also present an analysis of the colliding clusters 1E0657-558 (known also as the Bullet Cluster) and Abell 520; in both cases, the predictions of the MOG theory are in good agreement with observation.

Study of tacticity and thermal rearrangement of low molecular weight 1,2- polybutadiene by NMR

e-Polymers ◽  
2008 ◽  
Vol 8 (1) ◽  
Author(s):  
Farshid Ziaee ◽  
Hamid Salehi Mobarakeh ◽  
Mehdi Nekoomanesh ◽  
Hassan Arabi
Keyword(s):  
Double Bond ◽  
Theoretical Calculations ◽  
Group Formation ◽  
Methine Carbon ◽  
Order Markov Chain ◽  
Probable Reaction ◽  
Cis And Trans ◽  
First Time ◽  
Atactic Polymer ◽  
Good Agreement

AbstractLow molecular wieght 1,2-polybutadiene (Aldrich) tacticity was determined by 13CNMR (100.6 MHz). It was found that the olefinic methylene carbon has the highest splitting and a combination of pentad and heptad sequences was determined which is in agreement with the theoretical calculations. For the first time aliphatic methine carbon assignment of 1,2-polybutadiene was performed. Furthermore, olefinic methine carbon assignment was also performed and the results were compared with the theoretical calculations. For all carbons Bernoullian and first-order Markov-chain propagation statistics were used to fit the experimental data and a good agreement was obtained indicating an atactic polymer (Pm= 0.467). It was shown that the most probable reaction before gelation which happens by heating the polymer under vacuum at 250°C, is crosslinking accompanied with methyl group formation. The decrease in double bond intensity of the pendant group together with constant cis and trans double bond intensities were observed. During heating the syndiotactic triad sequences are consumed indicating that no cyclization has happened.

A SYSTEM OF MOLECULAR THERMOCHEMISTRY FOR ORGANIC GASES AND LIQUIDS

1956 ◽  
Vol 34 (5) ◽  
pp. 626-648 ◽  
Author(s):  
Keith J. Laidler
Keyword(s):  
Hydrogen Bonds ◽  
Heats Of Formation ◽  
Multiple Bonds ◽  
Aromatic Molecules ◽  
Tertiary Carbon ◽  
Systematic Effects ◽  
Heats Of Combustion ◽  
Organic Gases ◽  
Heats Of Vaporization ◽  
Good Agreement

An analysis has been made of the heats of formation and combustion of organic gases and liquids, and of the heats of vaporization of liquids. The work has been done as far as possible with homologous series, in order to discover systematic effects. The data are converted into heats of atomization, i.e., the heats required to convert the gases or liquids into their constituent atoms. It is shown that the heats of atomization of the gaseous aliphatic hydrocarbons (paraffins, olefins, and acetylenes) can be accurately represented by a scheme in which a distinction is made between primary, secondary, and tertiary carbon–hydrogen bonds, and between bonds that are next to, and next but one to, multiple bonds. For aromatic molecules an appropriate correction for resonance is proposed. For other types of compound it is found that suitable values for the various bonds (e.g., C–CHO, C–OH) will give rise to good agreement with experiment.It is shown that to a reliable approximation heats of vaporization are also amenable to the same treatment. Since this is so it is possible to assign bond values on the basis of which it is possible to make predictions about heats of formation of liquids.A system of coefficients is worked out by means of which the numbers of atoms of various kinds in a molecule can be expressed in terms of the numbers of the different kinds of bonds. On the basis of these it is shown how bond contributions to heats of formation and heats of combustion can be calculated. A table (Table X) gives the contributions proposed for the heats of atomization, heats of formation, and heats of combustion for both gases and liquids.

Bridged Polycyclic Compounds. XXXIV. Acetolysis of cis- and trans-β-Chlorodibenzobicyclo[2.2.2]octadienyl Thioethers1

1965 ◽  
Vol 87 (24) ◽  
pp. 5679-5684 ◽  
Author(s):  
Stanley J. Cristol ◽  
Ronald Caple ◽  
R. M. Sequeira ◽  
L. Oliver Smith
Keyword(s):  
Polycyclic Compounds ◽  
Cis And Trans
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