Dilute Benzene Research Articles

Photolysis of diarylcadmium compounds in benzene

Photochemical decomposition of selected diarylcadmium compounds in dilute benzene solutions was investigated. This reaction was found to involve initial cleavage of the aryl–cadmium bonds followed by coupling of the aryl radicals to give symmetrical biaryls in good yields. Arylation products were obtained in only 5–25% yields, in contrast with the photolysis of iodoaromatic compounds in benzene which gives arylation products in high yields. Diarylcadmium compounds derived from polynuclear aromatic compounds, e.g. di(p-biphenyl)cadmium and di(α-naphthyl)cadmium gave, under the same conditions, predominantly hydrogen transfer products. In carbon tetrachloride, photolysis of diarylcadmium compounds gave chloroarenes in high yields.

1‐Substituted 1‐(2‐Aminoethoxy)‐1‐sila‐2,8‐dioxa‐5‐azacyclooctanes ‐ proposed name: Pseudosilatranes

AbstractBy reacting equimolar quantities of R(R′O)2SiOCH2CH2NR2″ (R = CH3, C6H5, CH3O, C2H5O; R′ = CH3, C2H5; R″ = H, CH3) and Diethanolamine, appropriate 1‐substituted 1‐(2‐aminoethoxy)‐1‐sila‐2,8‐dioxa‐5‐azacyclooctanes, RSi[(OCH2CH2)2NR′](OCH2CH2NR2″) have been obtained for which the name “pseudosilatranes” has been proposed. The compounds are strongly associated in dilute benzene solutions.

Reaction of (5S)‐1‐azabicyclo[3.1.0]hexane with boron trifluoride etherate. Formation of an adduct and polymerization

AbstractThe ring‐opening polymerization of (5S)‐1‐azabicyclo[3.1.0]hexane (1) derived from L‐proline was attempted, by use of a catalytic amount of boron trifluoride etherate as an initiator, in order to obtain optically active polymers. Chiral polymers (2) were indeed easily formed when the above aziridine 1 was polymerized in bulk or in benzene. On the other hand, a stable BF3‐adduct was obtained in the form of colorless crystals when the dilute benzene solution (1%) of 1 was allowed to react with an excess of boron trifluoride etherate. The elemental analysis and the NMR (19F, 11B, and 13C) spectra of this adduct showed it to be a (5S)‐1‐azabicyclo[3.1.0]hexane‐boron trifluoride (1:1) complex (3). It was also found that the adduct initiated the polymerization of aziridine 1 more mildly than boron trifluoride etherate.

Specific aminic group - aromatic π system interaction in aliphatic amines or cyclohexylamines + benzene systems

By extrapolation of HE /x1 x2 vs. mole fraction, values for the partial molar excess enthalpy of aliphatic amines or cyclohexylamines at infinite dilution in benzene are obtained. Taking into account the dispersion effect and hydrogen bond contributions, the specific interaction aminic group — π (arom) system is calculated.

Michael‐Addition von Thiocarbonsäureestern Anwendung bei der Synthese von (±)‐Jasminketolacton

Michael addition of carbothioates. Application to the synthesis of (±)‐jasmine ketolactoneIt is shown that the lithium enolate of S‐t‐butyl thioacetate adds to 2‐cyclopentenone in the β‐position and that fluoride ions catalyze the 1, 4‐addition of the trimethylsilyl enol ether of S‐t‐butyl thioacetate (5) to 2‐cyclopentenone (4) to give 6. These novel versions of the Michael addition have been applied to a synthesis of jasmonoid compounds. Cleavage of the trimethylsilyl enol ether in 6 with tetrabutylammonium fluoride produced the corresponding ketone enolate which could be trapped in situ by alkylation with 1‐bromo‐5‐(2′‐tetrahydropyranoxy)‐2‐pentyne (7) to form 8. Removal of the alcohol protecting group in 8, followed by partial hydrogenation of the triple bond over Lindlar palladium and mercury ion promoted hydrolysis of the carbothioate moiety in 9, led to 5′‐hydroxy jasmonic acid (10, Scheme 3). 10 was converted into the S‐(2‐pyridyl) carbothioate and cyclized in dilute benzene solution under the influence of silver ion to give (±)‐jasmine ketolactone (1, Scheme 4), a component of the essential oil of Jasminum grandiflorum, in 72% yield. Similarly, methyljasmonate (2, Scheme 2) was obtained from 6 by the reaction with 1‐bromo‐2‐pentyne and tetrabutylammonium fluoride followed by methanolysis and partial hydrogenation of the triple bond.

Synthese von zwei natürlich vorkommenden Lactonen mit 10gliedrigen Ringen: (±)‐Phoracantholid J und I

Synthesis of Two Naturally Occurring 10‐Membered Ring Lactones: (±)‐Phoracantholide J and ITwo 10‐membered ring lactones 7 and 11 from the metasternal secretion of the eucalypt longicorn Phoracantha synonyma have been synthesized by the following method. Reaction of the dilithium derivative of 4‐pentynoic acid (3) with 4‐tetrahydropyranyloxy‐1‐pentylbromide (2), followed by removal of the protecting group and by esterification with diazomethane, gave methyl 9‐hydroxy‐4‐decynoate (4; s. Scheme 1). Partial hydrogenation of the triple bond in 4 with Lindlar palladium catalyst, followed by saponification lead to cis‐9‐hydroxy‐4‐decenoic acid (6). The 9‐hydroxydecanoic acid (9) was synthesized by addition of methyl magnesium iodide to methyl 8‐formyloctanoate (8) followed by saponification (s. Scheme 2). The hydroxy acids 6 and 9 were converted into the S‐(2‐pyridyl) thioesters and cyclized in dilute benzene solution under the influence of silver ions to yield (±)‐phoracantholide J (7) and I (11) in 74 and 71% yield, respectively.

Rotationsebulliometer, 1. Prüfung der Apparatur

AbstractA new pressure controlled twin‐ebulliometer without Cottrellpump is described. The apparatus is equipped with rotating vessels to establish complete equilibrium between liquid and vapour. The boiling temperature can be chosen by reducing the pressure by means of a pressure regulator in the range of 100–760 Torr.In SI‐Einheiten: 1 Torr=133,322 N/m2. The elevation of the boiling‐point is measured by two thermistors in a Wheatstone bridge circuit.Investigation of benzil and biphenyl in dilute benzene solution shows that the rotating ebulliometer permits operations within a boiling temperature range of 30–80°C.Measurements of polystyrene and poly(ethylene glycol) [poly(oxyethylene)] in benzene solution show that the rotating boiling vessel avoids the formation of foam. Therefore, the elevation of the boiling‐point of solutions of polymeric samples can be measured with this apparatus.

Microwave absorption and dielectric relaxation of some rigid molecules and their mixtures

The dielectric constant and loss factor of some rigid molecules, pyridine, quinoline, and isoquinoline, and their mixtures have been measured in dilute benzene solutions in the microwave region over a range of temperatures. The dielectric data have been used to determine the relaxation times and the thermodynamic parameters for the activated state. The values of the relaxation time for single polar component solutions agree well at temperatures at which there are available known data. The relaxation times for the mixtures are consistent with the results on simple liquid mixtures of polar molecules in dilute solutions which were previously studied by us and by some other workers.

On the molecular conformation of the bis-1,3-dioxolyl molecule in decahydronaphthalene and benzene solutions

The electric dipole moments of the bis-1,3-dioxolyl molecule were determined in dilute decahydronaphthalene solution at 25 and 100 °C and in dilute benzene solution at 25 °C. From the temperature dependence of the dipole moment it is concluded that the trans rotamer of the molecule is more stable in both solvents than the gauche rotamer by ∼4.5 kJ mol−1. The conformational behavior of the molecule is discussed in terms of a recently proposed solvation theory.

Behaviour of polystyrene on irradiation in diluted benzene solutions

Modifications due to the β-radiations of 204Tl on polystyrene in dilute benzene solutions have been studied by light scattering and viscometric measurements. Although the molecular weights of the samples are not affected, increase from 0.73 to 0.93 of the exponents of the Mark-Houwink equation was observed. From attempts to explain this high value of the exponent for irradiated polystyrene, it was concluded that the irradiated macromolecules show elongated shapes and higher chain flexibilities compared to unirradiated polystyrene.

Molecular motions in liquid. I. Rotation of water and small alcohols studied by deuteron relaxation

The deuteron spin lattice relaxation time T1 of CH3OD, C2H5OD, (CH3)2CHOD, and (CH3)3CHOD is reported as a function of temperature and frequency. The deuteron T1 of the alcohols in dilute benzene solutions was also measured at 25°C. A detailed analysis of the experimental results and other magnetic and dielectric relaxation data from the literature was made. Based upon the analysis, it is suggested that the success of the Debye model in explaining the dielectric and magnetic relation behavior of water and small alcohols may be purely coincidental. It seems that the error in applying Stokes law for the rotation of a macroscopic sphere to small molecules in liquid and the error in assuming that water and alcohols rotate as monomers largely cancel each other, yielding much better apparent agreement between calculated and experimental data than those for nonassociating liquids. The deuteron T1’s for the alcohols are further analyzed in terms of anisotropic rotation.

Dielectric relaxation of some aliphatic ketones in dilute solutions

The dielectric relaxation behavior of 2-butanone, 2-pentanone, 2-heptanone, and 3-nonanone in dilute nonpolar solvents, n-heptane, cyclohexane, benzene, and carbon tetrachloride has been studied in the microwave region at a number of temperatures. The relaxation data have been used to estimate the free energy, enthalpy, and entropy of activation for the relaxation mechanism. The values of the relaxation time for those solutions for which there are available known data agree well with other determinations. The results have been discussed in terms of dipole reorientation by intramolecular and overall molecular rotation and compared, wherever possible, with other similar studies on aliphatic molecules.

The i.r. spectrum and molecular conformation of bis-chloromethyl ether

The i.r. spectra of bis-chloromethyl ether (ClCH 2) 2O have been recorded in the vapour, liquid and solid phases, in the region 4000-200 cm −1. The spectra indicate the presence of a conformational equilibrium between two rotameric forms, with the more stable rotamer having a gauche—gauche configuration with the two chlorine atoms opposed. A trans-gauche conformation is suggested for the less stable, but more polar, second rotamer. The dipole moment of bis-chloromethyl ether in benzene solution at 294 K was measured to be 1·29 ± 0·5D(4·30 ± 0·17 × 10 −30 Cm). From this value the energy difference between the two forms in dilute benzene solution is estimated to be 3·8 kJ mol −1. The energy difference in the vapour phase seems to be considerably larger.

Rotational isomerism in propargyl formate as studied by infrared and microwave spectroscopy

The microwave and infrared spectra of propargyl formate have been studied in the respective ranges 40–15 GHz and 4 000–50 cm–1. Evidence is presented for the coexistence of rotational isomers, one of which (probably the more stable) is shown to have a planar arrangement of heavy atoms with the alkyl group s-cis with respect to the carbonyl bond and with the acetylenic group directed away (trans) from the carbonyl group. The dipole moment was measured in dilute benzene solution at 297 K to be 1.94 ± 0.02 D.

Electric Dipole Moments of Some Substituted Trifluoromethylbenzenes

AbstractThe dipole moments of 3‐nitro‐4‐fluoro‐, 2‐fluoro‐5‐nitro‐, 2‐amino‐5‐fluoro‐, 2‐fluoro‐5‐amino‐, 3‐amino‐4‐fluoro‐, 2‐amino‐, and 2‐amino‐5‐bromotrifluoromethylbenzene were determined in dilute benzene solutions at 25 C. In addition the total energy and the electric dipole moment of the first six compounds mentioned above were calculated using the INDO molecular orbital approximation. It was found that with the exception of the two nitro‐substituted trifluoromethylbenzenes there was fair to excellent agreement between the measured and calculated values of the dipole moments.

Photochemical reactions of aromatic compounds. Part XVIII. Photoaddition of benzophenone to aromatic amines

Photoreactions of benzophenone with diphenylamine or 2,6-dimethylaniline in t-butyl alcohol or acetonitrile solution result in the formation of triarylmethanol (I). Irradiation of dilute benzene solutions gave mainly brown intractable materials, and, in the case of diphenylamine, some benzopinacol (1,1,2,2-tetraphenylethane-1,2-diol). With aniline, NN-dimethylaniline, the three isomeric toluidines, N-methyldiphenylamine, triphenylamine, and 2,3- and 2,5-dimethylanilines, the formation of a triarylmethanol (I) was not observed. From the solvent-dependence of the reaction, the structural limitation of aromatic amines for the formation of (I), and kinetic results, the following mechanism is suggested: in polar solvents, an exciplex formed between triplet benzophenone and diphenylamine or 2,6-dimethylaniline effectively becomes an ion-pair, and this is followed by proton transfer in an ion-pair giving a radical-pair in a solvent-cage (IV) which couples to afford (I).

ChemInform Abstract: DIPOLE MOMENT OF N‐(P‐METHOXYBENZYLIDENE)‐P‐BUTYLANILINE

Chemischer InformationsdienstVolume 4, Issue 47 Physical Organic Chemistry ChemInform Abstract: DIPOLE MOMENT OF N-(P-METHOXYBENZYLIDENE)-P-BUTYLANILINE P. MAUREL, P. MAURELSearch for more papers by this authorALUN H. PRICE, ALUN H. PRICESearch for more papers by this author P. MAUREL, P. MAURELSearch for more papers by this authorALUN H. PRICE, ALUN H. PRICESearch for more papers by this author First published: November 20, 1973 https://doi.org/10.1002/chin.197347080AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume4, Issue47November 20, 1973 RelatedInformation

Quantum yields of resonance Raman scattering in the case of 1,1,14,14 tetraphenyltetradecaheptaene

Resonance Raman scattering (RRS) of 1,1,14,14 tetraphenyltetradecaheptaene in dilute benzene solution was studied. The visible and UV lines of an Ar + laser were used to irradiate into the electronic absorption band. Absolute RRS cross sections were determined by comparison with Raman lines of the solvent. From such cross sections quantum yields for RRS were derived. Within the electronic absorption band the total RRS quantum yield has a mean value of 5 × 10 −6. From this a non-radiative rate constant of 2 × 10 14 sec −1 is estimated. It is suggested that internal conversion is the radiationless process which competes with RRS.

ChemInform Abstract: ELECTRIC DIPOLE MOMENTS AND CONFORMATIONS OF ORTHO‐, META‐, AND PARA‐FLUOROACETOPHENONES AND OF ORTHO‐, META‐, AND PARA‐TRIFLUOROMETHYLACETOPHENONES

The dipole moments of ortho-, meta-, and para-fluoroacetophenone and of ortho-, meta-, and para-trifluoromethylacetophenone were determined in dilute benzene and carbon tetrachloride solutions at 2...

Electric Dipole Moments and Conformations of ortho-, meta-, and para-Fluoroacetophenones and of ortho-, meta-, and para-Trifluoromethylacetophenones

The dipole moments of ortho-, meta-, and para-fluoroacetophenone and of ortho-, meta-, and para-trifluoromethylacetophenone were determined in dilute benzene and carbon tetrachloride solutions at 25 °C. In addition the dipole moments and the total energies of the above molecules and of acetophenone, fluorobenzene, and trifluoromethylbenzene were computed for different molecular conformations by the INDO molecular orbital approximation. In some cases there is quantitative agreement between the experimental dipole moments and the INDO computed dipole moments. The most probable conformation for different fluoroacetophenone and trifluoromethylacetophenone molecules is suggested.