Showing papers on "Cyclopropane published in 1969"

Optical and Photoelectron Spectra of Small Rings. III. The Saturated Three‐Membered Rings

Abstract: The electronic states of cyclopropane, ethylene oxide, ethylenimine, and diaziridine were investigated using gas‐phase and condensed‐phase vacuum ultraviolet spectroscopy, photoelectron spectroscopy, and Gaussian orbital self‐consistent field calculations. Correlation of the gas‐phase and condensed‐phase optical spectra of cyclopropane with the first band in its photoelectron spectrum confirms the presence of Rydberg transitions in the optical spectrum involving excitation of an electron from the 3e′ sigma level. The valence shell spectrum of cyclopropane is complex but is dominated by two very strong 1A1′ → 1E′, σ → σ*, excitations. The Rydberg spectrum of ethylene oxide is reassigned to include the two absorptions in the 55 000–65 000‐cm−1 region, all bands originating from the 2b2π orbital, while its valence shell spectrum is closely related to that of cyclopropane. Similar but less conclusive results were obtained for ethylenimine. Virtual orbital calculations of σ → σ* excitation energies gave result...

Microwave Spectrum and Structure of Bicyclo[1.1.0]butane

Abstract: The microwave spectra of four isotopic species of bicyclo[1.1.0] butane have been investigated and the rotational constants of each species have been determined. Combining these data with those of the previously studied normal isotopic species, a complete set of structural parameters have been found. These include C1–C3 = 1.497 A, C3–C4 = 1.498 A, C3–C6 = 1.071 A, C–H (methylene) = 1.093 A, ∠C1C3H6 = 128°22′, dihedral angle, α, between cyclopropane rings = 121°40′, ∠HCH = 115°34′. These results are discussed with regard to the electronic structure of the molecule.

Process for the preparation of cyclopropane derivatives and compounds produced therein

Abstract: Process for the preparation of racemic or optically-active cyclopropane carboxylic acid of the formula ##STR1## wherein the CO 2 H substituent on the carbon 1 and the ##STR2## substituent on the carbon 2 are in the cis-position relative to one another, R 1 represents a hydrogen, an alkyl radical, an aralkyl radical, an aryl radical, an alkenyl radical, an alkynyl radical, a cycloalkyl radical, a cycloalkenyl radical, a heterocyclic radical, these radicals being able to be substituted, specifically by lower alkyl or lower alkoxy, or represents a cyano group, an acyl group, a formyl group, an alkoxycarbonyl group or a nitro group, and Z represents the R 2 residue which has the same meaning as R 1 but is identical or different thereto, or the R 3 residue, which represents an allyl radical, a benzyl radical, a cyano group, an acyl group, a formyl group, an alkoxycarbonyl group, or a nitro group, or R 1 and Z together form a saturated or unsaturated carbon homocycle or heterocycle, whose ring can support substituents such as lower alkyls or lower alkoxys, or functions such as ketonic functions, or together form a polycyclic aromatic residue such as a fluorene residue.

Partial Asymmetric Synthesis in the Simmons-Smith Reaction. III. A Modification of the Reaction

Abstract: A modification of the Simmons-Smith reaction, which involves a prior reaction of ethyl iodide with zinc copper couple followed by addition of methylene iodide and oleflns, was proposed. The improved yields of cyclopropane products were obtained with various olefin substrates. It is likely that the operating species in the present modification is ethyliodomethylzinc.

The electronic structure of cyclopropane, cyclopropene and diazirine an ab initio SCF-LCAO-MO study

Abstract: The electronic structure of cyclopropane, cyclopropene and diazirine has been studied within the ab-initio SCF-LCAO-MO theoretical framework. The present results lead to a general bonding model for three-membered ring systems. Composition of the MO's, population analyses and electron density distribution diagrams were used to establish the nature of the bonding. The total electron density distributions in cyclopropane and in cyclopropene lead to a “bent bond” + “central hole” bonding model; however the bending angle is only ca. 5° and the central hole is not very deep with respect to the bonding regions (ca. 15% density depression). Special emphasis has been given to the nature of the σ bonds forming the ring system. It has been found that the ring bonding in cyclopropane and in cyclopropene is due principally to three MO's: (1) A low lying MO (3a1) composed mainly of C(2s) AO's and contributing electron density principally inside the ring triangle. (2) Two MO's (6a1 and 3b2), which are the highest occupied MO's in cyclopropane and lie immediately below the π bond in cyclopropene, composed almost exclusively of C(2p) AO's in the ring plane and leading to electron density maxima outside the ring (density bending angle of ca. 20°) and to zero density in the centre of the ring. In the case of diazirine these MO's are appreciably perturbed by the presence of the nitrogen lone pairs. Three MO's contribute mainly to the description of the lone pairs, all of which also contribute to some extent to ring bonding. Furthermore, among these three MO's two lie below the π level, one of them being very low in energy. This is quite different from the usual picture. The present bonding picture has been compared to former semi-empirical models (especially the Coulson-Moffitt and the Walsh models). The strain, the “π” character and conjugative properties of the three-membered ring are discussed on the basis of its electronic structure. The special bonding features of this system confer on it a pseudo-π(ψ-π) character; the bonds making up the ring may be considered as ψ-π bonds.

Non empirical LCAO-MO-SCF calculations with gaussian type functions on some three membered ring heterocycles

Abstract: Non empirical molecular quantum chemical calculations have been performed on the three membered ring heterocyclic molecules, aziridine, oxirane and thiirane and the as yet unknown 1 azirene, 2 azirene, oxirene and thiirene. For the nitrogen compounds the corresponding protonated species have been investigated and for comparison the isoelectronic saturated and unsaturated hydrocarbon molecules, cyclopropane and cyclopropene. A discussion is given of total energies, eigenvalues, and gross atomic populations.

Mass spectrometry of aralkyl compounds with a functional group—VII. On the structure of the ions C8H9+ from C6H5C2H4X‐ and C9H11+ from C6H5C3H6X‐compounds

Abstract: The C8H9+-ion, formed from the molecular ions of 2-phenyl-1-bromoethane, 1-phenyl-1-bromoethane and of 1-phenyl-1-nitroethane by loss of the bromine atom and of the nitro group, splits off a molecule of acetylene after an almost complete randomization of hydrogens, as proved by deuteration. An eight-membered ring structure for the C8H9+-ion is proposed to explain these results. By loss of the nitro group from the molecular ions of 1-phenyl-1-nitropropane and of 1-phenyl-2-nitropropane the well-known phenylated cyclopropane ion3 (C9H11)+ is generated. Mass spectra of analogues, specifically deuterated in the side-chain, show that in this ion a randomization of hydrogen atoms in the cyclopropane ring as well as a hydride transfer from the cyclopropane ring to the phenyl cation occur.

Kinetics of the thermal decomposition of cyclobutanone

Abstract: The thermal decomposition of cyclobutanone into cyclopropane and carbon monoxide has been shown to occur simultaneously with the major decomposition to ethylene and ketene. The relative rate consta...

Cyclopropane chemistry. Part I. Thermal isomerisation of gem-dichlorocyclopropanes to olefins

Abstract: A series of 1,1-dichlorocyclopropanes containing various ring substituents has been prepared and the compounds have been pyrolysed in a flow system at 500–670°. This pyrolysis is a useful route to olefins. 1,1-Dichlorocyclopropane gives 2,3-dichloropropene in high yield. Cyclopropanes containing more chlorine substituents also give, in each case, a high yield of a single olefin isomeric with the cyclopropane; for instance 1,1,2-trichlorocyclopropane gives 1,1,3-trichloropropene, the 1,1,2,2-tetrachloro-compound gives 1,1,2,3-tetrachloropropene, and 1,1,2-trichloro-2-chloromethylcyclopropane gives 1,1,3-trichloro-2-chloromethylpropene. Cyclopropanes which contain other substituents give mixtures of isomeric olefins. For instance 1,1-dichloro-2-methylcyclopropane gives 2,3-dichlorobut-1-ene and 1,2-dichlorobut-2-ene. The results are interpreted in terms of a unimolecular concerted chlorine-atom migration and ring-opening mechanism.

Dielectric and nuclear magnetic resonance properties of a clathrate hydrate of cyclopropane

Abstract: Dielectric relaxation data and proton magnetic resonance spectra are given for the structure I clathrate hydrate of cyclopropane. Vapor pressures have been measured along the structure I – structur...

Reaction of 1,1-dicyclopropylethylene with pentacarbonyliron: a novel carbon monoxide insertion coupled with a double cyclopropane ring-opening

Abstract: 1,1-Dicyclopropylethylene reacts with pentacarbonyliron to give 2-cyclopropylpenta-1,3-dienetricarbonyliron (V) and, after a longer reaction time, a mixture of (V) and 3-(1′-propenyl)-cyclohex-2-enonetricarbonyliron—a carbon monoxide insertion reaction.

Photochemical transformations. Part XXVI. Some 19-substituted lanostane derivatives

Abstract: Photolysis of 3β-acetoxylanostan-11 β-yl nitrite affords 3β-acetoxy-19-hydroxyiminolanostan-11β-ol. From this compound 19-nitrilo- and 19-amino-derivatives have been prepared. The method of forming the 9β,10β-cyclopropane ring by deamination of 19-aminolanost-9(11)-en-3β-ol, as previously reported, does not lead to cyclopropane derivatives.