Electrogeneration of triplet states of intramolecular anthracene-amine systems

In the electron transfer between the cation radicals

of the amine moiety of four intramolecular anthra cene-amine systems and the anion radicals B^XXX of some heterocyclic and carbonyl compounds in acetonitrile/toluene, the triplet state of the anthracene moiety

is formed. As intermediates in this process, intramolecular and intermolecular triplet exciplexcs

or

and

or

are discussed.     

A direct synthesis of 1,3-bis(bromomagnesio)propane

Careful addition of 1,3-dibromopropane

to magnesium in Et₂O yields 1,3-bis(bromomagnesio)propane

which is purified via “magnesacyclobutane”

. Reactions of

with H₂O, CO₂, HgBr₂ and Me₃SnCl are reported. MgBr₂ catalyses the decomposition of

to allylmagnesium bromide

.     

The preparation of fluxional tetrahydrides, (R  H or Me) and their reactions with CO,ButNC or HBr

The cyclometallated monohydrides

(R  H or Me) react with NaOPrⁱ/PrⁱOH/H₂ to give fluxional tetrahydrides, probably

. These are highly fluxional having magnetically equivalent hydridic hydrogens, even at ---100°C. When treated with HBr,

, gives

and with CO it gives a mixture of complexes which are probably

(2 isomers) and

. When treated with Bu^tNC this tetrahydride undergoes similar reactions but another (major) product is formed which appears to be binuclear and fluxional and is probably of type

, with four bridging hydrogens.     

The composition of the evolved gases from the thermal decomposition of certain metal sulfates

By the use of TG—MS, the thermal dissociation of anhydrous CuSO₄ and Al₂(S0₄)₃ was found to proceed according to the reactions:

followed by the reactions:

No SO₃ was indicated in the dissociation of alunite. The sulfate ion appears to dissociate by at least two different mechanisms although the parameter which controls the mechanisms has not been elucidated.     

The preparation of perfluorinated esters of fluorine containing tertiary alcohols

The reaction of an aromatic lithium reagent, LiR, with a perfluoroacid anhydride (RfCO)₂O, in ether solution at low temperatures, produces esters of composition

in addition to the expected ketone

. Mixed esters of composition

may be prepared by starting with a ketone

and reacting with a lithium reagent LiR followed by perfluoroacid anhyride (RfCO₂O. Hydrolysis of the esters provide a convenient route to trertiary alcohols of composition Rf(R) ₂COH.     

Some chlorine fluorosulfonate and peroxydisulfuryl-difluoride reactions

Chlorine fluorosulfonate adds exceptionally easy not only to various alkenes, perfluorobenzene, but to alkynes too

The addition of peroxydisulfuryldifluoride to alkyl- and perfluoroalkyliodides leads to unstable adducts, which decompose with the formation of alkylfluorosulfonates and iodine fluorosulfonate; the latter was trapped with fluoroalkenes

The use of ClOSO₂F allows to substitute selectively for the fluorosulfonate group the chlorine atom in monochloroacetic acid esters as well as the fluorine atom in hexafluoroacetone N-fluoroimine

ClOSO₂F serves as an exceptionally active chlorinating reagent for fluorinated alcohols, nitrosocompounds, perfluoroacid amides and particularly for benzene

The reaction of (OSO₂F)₂ with perfluoroacid amides leads to the corresponding N,N-bis(fluorosulfonate)amides, which easily rearrange into alkylfluorosulfonates

The hypochlorites of fluorinated alcohols are stable enough and they, similarly to ClOSO₂F, are able to add to alkenes, fluoroalkenes (but not to perfluoroisobutylene), bis(trifluoromethyl)ketene, trifluoromethylisocyanate and perfluoronitriles

The fluorosulfonatoacetic acid esters are unstable at the ambient temperature, but they can be widely used in situ as a very effective alkylating reagents

     

Synthesis and intramolecular charge-transfer interaction of o-tropyliobiphenyl tetrafluoroborates

A series of o-tropyliobiphenyl tetradfluoroborates

has been synthesized. Evidences are presented to show that

exhibit strong intramolecular charge-transfer interaction between tropylium ion and remote aryl ring. The structure of

was determined by single crystal X-ray diffraction study.     

Excited-neutral-metastable SO2 formation in the , O3-olefin-SO2, and active nitrogen-SO2 systems

Long-liied (τ > 10^?3 s), electronically-excited (E * > 4 eV) neutral metastables, whose formation was attributed to the presence of SO₂, were observed in the three titled systems. Their possible identity as collisionally-accessed metastable states of the normal

, cyclic

, or superoxide

isomers of SO₂ is discussed.     

Laser flash photolysis of iodine-iodide mixture in hydroxylic solvent. Evidence for the existence of the radical anion I

The laser flash photolysis of iodine-iodide mixtures in alcoholic solvents produces transient species absorbing in the red and near infrared region with maxima at 740 and 590 nm. The 740 nm absorption band has already been attributed to the well known I

ion. In this work the 590 nm absorption band is assigned to the I

radical anion which presumably could be formed by the equilibrium reaction: I

+ I₃^- ? I

. The variations of the intensities of the 590 and 740 nm transient absorption bands as a function of I₃^? concentration, temperature and solvent, support this assignment. The kinetics of formation of I

and I

has been studied in solutions of tertiary butanol. An analysis of the experimental results shows that the I

ion could be formed via a mechanism involving an I

intermediate.     

Doping-addition of arylsulfenyl chlorides to the tricyclo[4,2,2,02,5]deca-3,7,9-triene system: skeletal rearrangements and serendipitious products

“doping-addition” of 2-NO₂C₆H₄SCl to the tricyclo[4,2,2,0^2,5]deca-3,7,9-triene system

occurs to give unusual products: (i) rearranged caged cyclopropane

and (ii) the stable cross-perchlorate

.     

Electrokinetic phenomena in porous membranes: Determination of phenomenological coefficients and transport numbers

Electrokinetic phenomena in porous membranes were studied in the framework of the linear thermodynamics of irreversible processes. Phenomenological coefficients of two commercial porous membranes were determined. The variation of these coefficients with the different concentrations of NaCl used was also studied. Onsager's reciprocal relationship between cross-coefficients holds within the limits of experimental error.Membrane potentials were measured at concentrations ranging from 10^?3M to 75 X 10^?3M. The apparent transport number of the cation,

, was calculated from the diffusion potential expression. An electrometric method was used to obtain the true cation transport number,

, and the water transport number,

, for different solution concentrations, ranging from 15 x 10^?3M to 75 x 10^?3M. The true transport number of the cation,

, was also determined, taking into account water transport across the membrane. A good agreement was found between

and

values.     

Gas phase electron diffraction study of tetraphenyltin,Sn(C6H5)4

The geometrical parameters of the tetraphenyltin molecule have been determined by gas phase electron diffraction at about 310°. The S₄ and “open” D_2d molecular models with the tetrahedral bond configuration at tin were chosen for the structure analysis. The former gave the better fit. The thermal average bond lengths (r_g, in Å) are as follows:

The benzene ring geometry appears to be almost unaffected by bonding to tin. However, tin causes an increase in the endocyclic valence angle at the ipso-carbon atom to 121.0(0.9)° rather than a decrease of that angle as might be expected, tin being a σ-electron donor. The ring plane and the plane containing the

bond and S₄ axis make an angle, ?, of 34.1(2.1)°. The

bond length in tetraphenyltin is longer than not only the

bond in tetravinyltin (r_g = 2.117(4) Å) but also the

bond in tetramethyltin (r_g = 2.144(7) A).     

Gas phase electron diffraction study of tetravinyltin Sn(CHCH2)4

The tetravinyltin molecule has been studied by gas phase electron diffraction. The r_a structure analysis is based on the assumptions that a single conformer occurs in Sn(CHCH₂)₄ and that tin has a tetrahedral bond configuration. The preferred model (S₄ symmetry) predicts all four vinyl groups to be intermediate between staggered and eclipsed conformations. The structure refinement gives the following parameters (bond lengths, r_a, in nm, valence angles in degrees):

, SnCC = 121.9(0.6), CC = 0.1349(8), SnCH = 116.8(4.5),<C—H?_av. = 0.1098(14). The uncertainties given in parentheses represent three times the standard deviation values.The observed shortening of the

bond in Sn(CHCH₂)₄ from

in SnMe₄ (by 0.0027 nm) is equal to the shortening that occurs on going from

in ethane to

in propylene. With the corresponding Si and Ge derivatives, this effect is less pronounced.     

Synthese de la phenyl-2-dimethyl-4,5-phosphorine a partir du benzyl-1-dimethyl-3,4-phosphole

1-Benzyl-3,4-dimethylphosphate

-$\text{1}$ is converted into 2-phenyl-4,5-dimethyl-λ₃-phosphorin

-$\text{2}$ through 1,2-dihydro-λ₅-phosphorines

$\text{3}$ and

$\text{s}$.     

Enthalpies de formation du nitrate d'yttrium hexahydraté et de l'ion Y3+

The dissolution enthalpies of yttrium and hexahydrated yttrium nitrate in nitric acid at different concentrations have been measured and the following enthalpies have been determined:

     

Determination de l'enthalpie de formation standard du tetrafluorure de tellure par calorimetrie de combustion dans le fluor et par calorimetrie de reaction

The standard enthalpy of formation of tellurium tetrafluoride has been determined: by combustion in fluorine:

by reaction in a normal solution of soda:

     

Monofluoration stereoselective par le phenyltetrafluorophosphorane (PhPF4) Part. II. Application a la synthese des isomeres thréo et érythro des alkyl-2 fluoro-3 phenylpropanoates de methyle. Analyse conformationnelle par R.M.N. de 19F et 1H.

The stereoselective fluorination of four couples of diastereoisomeric 2-alkyl 3-hydroxy 3-phenylpropanoic methyl esters

by the reaction of the phenyltetrafluorophosphorane with the corresponding trimethylsilylethers derivatives

is described. The structure of the 2-alkyl 3-fluoro 3-phenyl propanoic methyl esters

obtained quantitativly has been determined unambiguously by NMR analysis. ¹⁹F NMR results permit us to determine the relative populations of the rotamers for each of the isomers threo and erythro.     

Diversity of the gramicidin a spatial structure: two-dimensional 1H nmr study in solution

Theoretical consideration reveals a unique relationship between NMR spectral parameters and possible types of the gramididin A spatial structure. By means of two dimensional NMR spectroscopy four distinct species were detected simultaneously in ethanol solution. Comparison of experimental data and theoretical conclusions demonstrates that species 1 and 2 are left-handed parallel double helices

differing in relative arrangement of the two polypeptide chains within the dimers, species 3 is left-handed antiparallel double helix

, and species 4 is a mirror image of species 1, i.e. right-handed parallel double helix

. The results are compared with those on spatial structures of the peptide in complex with cesium (right-handed antiparallel double helix

) and of the gramicidin A transmembrane ionchannel (N-terminal to N-terminal single-stranded dimer

).     

Gas phase electron diffraction study of trimethylstannylacetylene

Trimethylstannylacetylene has been studied by gas phase electron diffraction. The bond lengths, r_a (Å), and valence angles (degrees) determined with errors represented by three times standard deviation values are as follows:

.The results are compared with the structural data on organotin compounds studied earlier. The

bond lengths are shown subject to different substituent effects.     

η2-acylcarbonylvanadium-verbindungen

Substituted vanadium carbonyl compounds with η²-bonded acyl ligands (η²-RCO)V(CO)₃

(

= ditertiary phosphines or arsines: dppe, dppp, dppm, diars, arphos, dpase) have been prepared by photochemical reaction of [V(CO)₄

] with various substituted benzoyl chlorides and cyclopropanylcarbonyl chloride.Effects of aromatic substituents and

upon the thermal stability of the η²-acylcarbonylvanadium compounds are discussed. IR ν(CO) force constants and ⁵¹V NMR signals are linearly correlated with Hammett's σ constants of the aromatic substituents.The preparation of V(CO)₂Cl(diars)₂ is described.