Solvents formation

Donor solvent Formation constant X(20°C)/1 mol- -AH / kJ moC Charge-transfer band W/nm fmax A VI/cm- 2 ... 

Because Me3SiCl 14 is almost inert to lithium organic compounds or Grignard reagents in non-polar solvents, formation of tertiary alcohols on addition of MeLi or n-BuLi to free carboxylic acids [127] or their methyl or ethyl esters [128] in THF... 

Homo- and heteroleptic complexes of Cd alone and of Cd and Hg with the ligand dicyanamide (dca) N(CN)2-, homologous to cyanamide NCN2-, have been studied in various solvents (formation constants of the complexes [M(dca) ](" 2> (M = Cd, Hg l < n < 4)), with the result that the complexes of Hg are more stable than those of Cd. Otherwise, obviously no studies on the isolated compounds M(dca)2 or on homoleptic complexes derived therefrom have been published. 

Trivino GC, Klabunde KJ, Dale EB (1987) Living colloidal palladium in nonaqueous solvents. Formation, stability, and film-forming properties. Clustering of metal atoms in organic media. 14. Langmuir 3 986-992... 

Relative contribution of each of these structures differs significantly and is determined by internal structural characteristics of the nitrones and by the influence of external factors, such as changes in polarity of solvent, formation of a hydrogen bond, and complexation and protonation. Changes in the electronic stmcture of nitrones, effected by any of these factors, which are manifested in the changes of physicochemical properties and spectral characteristics, can be explained, qualitatively, by analyzing the relative contribution of A-G structures. On the basis of a vector analysis of dipole moments of two series of nitrones (355), a quantum-chemical computation of ab initio molecular orbitals of the model nitrone CH2=N(H)0 and its tautomers, and methyl derivatives (356), it has been established that the bond in nitrones between C and N atoms is almost... 

In spite of the difficulties mentioned above, Brookhart and co-workers succeeded in measuring the barrier for ethene insertion into (dppp)PdC(0)CH3+ at 160 K, starting from the ethene adduct, generated at still lower temperatures, in the absence of CO. The barrier measured (AG ) amounted to only 51.4 kJ/mol, i.e. the reaction is faster than the insertion of CO in an ionic alkylpalladium complex. The barrier of insertion of ethene into a palladium methyl species or palladium ethyl species was higher, at 67 kJ/mol at 233 K. As for the CO insertion described above, these values concern the barriers in preformed ethene adducts at higher temperatures the overall barrier will be higher, because alkene coordination will be disfavoured by entropy and competition with CO and solvent. Formation of CO adducts will also be less favourable at higher temperatures. 

Electrophilic addition of the halogens and related X—Y reagents to alkenes and alkynes has been a standard procedure since the beginning of modem organic chemistry.1 Anti electrophilic bromination of such simple compounds as cyclohexene and ( )- and (Z)-2-butene, and variants of this reaction when water or methanol are solvents (formation of halohydrin or their methyl ethers, respectively), are frequently employed as prototype examples of stereospecific reactions in elementary courses in organic chemistry. A simple test for unsaturation involves addition of a dilute solution of bromine in CCU to the... 

Excimer-forming complexes (GS = the ground state) Multiplicity of excimer Solvent Formation (K) and decay rate (k, in s ) constants Ref. 

The direction of elimination of the /1-hydrogen to give either enol ethers or allylic ethers from alkenes can be controlled by using DMSO as a solvent. Formation of the allylic ether 47 was utilized in the synthesis of the tetronomycin precursor 47 from 46 [47], The oxidation of optically active 3-alkene-l,2-diol 48 afforded the 2,5-dihydrofuran 50 with high ee. It should be noted that /1-OH in 49 is eliminated to... 

The advantages of this industry scale synthesis are the use of non-halogenated solvents, formation of inert inorganic salts as waste products, recycling of valuable side products, ambient temperatures, relinquishment of protecting groups and purification by crystallization or filtration. 

Gottwald, M., and Gottschalk, G. 1985.The internal pH of Clostridium acetobutylicum and its effect on the shift from acid to solvent formation. Arch. Microbiol., 143, 42-46. 

Due to the low solubility of cobalt(II) fluoride in most solvents, formation of cobalt fluoro N-donor complexes (which are the only low-valent cobalt fluorides which are reliably reported) features a variety of starting materials. A common theme that runs throughout this work has been the use of [Co(BF4)2] as the fluoride source, and the subsequent controlled decomposition to obtain a metal-bound fluoride. This has been done, for example, with tris- (3,5-dimethyl-pyrazol-l-yl)methyl amine (amtd) to give [M2(amtd)2F(BF4)3(EtOH)Y(H20)] (M = Co, Cu, Zn x = 0-1.5, y = 1-2). The cobalt complex has been structurally characterised by X-ray diffraction [Fig. 3] [57]. Similarly, the combination of [M(BF4)2] (M = Mn, Co, Ni), [M(N03)2], NH4(NCS) and 3,5-diethyl-1,2,4-triazole (detrH) produces... 

Nucleophilic participation of HMPT has been reported in dipolar aprotic solvents. Formation of a sulfonium salt has been observed in an acid-catalyzed reaction in DMSO. Another research group has examined the nucleophilic splitting of stereoisomeric 3-methoxycyclopentene and hexene oxides. Detailed studies have been performed on the geometry of the transition state in the reactions of cyclopentene and cyclohexene oxides, and their competitive opening by charged and neutral nucleophiles in acidic aqueous methanol. Other authors have dealt with the opening of epoxynorbornenes and the nature of the inter-... 

Photocatalytic reduction of carbon dioxide on TiO-, nanocrystals embedded in Si02 matrices (Q-Ti02/Si0,) and bulk CdS particles with and without surface modifieation by several thiol compounds was investigated in various kinds of solvents. Formate and carbon monoxide were obtained as the major reduction products and the ratio of the former to the latter was increased with an increase in the dielectric constant of the solvents used for the use of Q-Ti02/Si0, and bare CdS particles as photocatalysts. The surface modification of CdS particles with thiol compounds was effective in enhancing the ratio of formate to carbon monoxide. The observed selectivity of CO2 reduction products was explained well in terms of the stabilization of reaction intermediates on the photocatalyst surface. 

Energy is required to disrupt the structure of the pure solute and solvent, and energy is released due to the attractive interactions between the solute and solvent. Formation of a solution can be endothermic or exothermic, depending on the difference between these energies. 

Hayami, J., Koyanagi, T., Hihara, N., Kaji, A. Substrate-nucleophile association in the Finkelstein reaction system in a dipolar aprotic solvent. Formation of complex between substituted chloromethanes and halide ion in acetonitrile. Bull. Chem. Soc. Jpn. 1978, 51, 891-896. 

Thallium(i) forms precipitates (T1X) and soluble complexes (T1X2) with the anions Cl , Br, T, and Nj in dimethylacetamide as solvent. Formation constants have been calculated for all of these species.608... 

Consider the transformation shown below. When CH2C12 is the solvent, formation of 7 occurs exclusively. Use of toluene or diethyl ether as solvent results in a mixture of 7 and 8, with 7 usually predominating. The investigators postulated a mechanism for S02 insertion that was different than the SE2 pathway discussed in Chapter 8.10S... 

Fojtik, A. Henglein, A. Laser ablation of films and suspended particles in a solvent Formation of cluster and colloid solution. Ber. Bunsenges. Phys. Chem. 1993, 97(1, 252-254. 

As a matter of fact, the use of LLE as an extraction technique shows several drawbacks, i.e., the long time necessary to perform the extraction, the use of relatively large volumes of expensive and potentially toxic solvents, formation of emulsions resulting in analyte losses, extensive use of glassware which can contaminate the sample, magnification of solvent impurities, need of sample preconcentration prior to analysis, evaporative losses of analytes, not always satisfactory repeatability, and loss of sensitivity as a consequence of the injection of only fractions of the extracted compounds. 

The stability of DMSO solvates of AgC104 have been measured in a range of solvents. Formation constants are presented in Table 37. In general, the complexes were found to be more stable than the corresponding DMF species (see Section 54.1.4.8.ii). 

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