Organic dimers

To gain insight in the trapping activities of lithiiun organyls and also of ketones, azides, or organic dimers, we produced the standard silaethene in the presence of two different traps in diethyl ether at -78 C (Eq. 1). 

Slater determinant, 258 Slater orbitals, 158, 159 Space groups, 285 common organic, 325 symmorphic, 288 Space symmetry operator, 286 Spectra, of crystals, 306 of organic dimers, 321 polarization of, 306 Spherical harmonics, 143ff Spin angular momentum in molecules, 188-169... 

An unusual compound is a Sn]II) cationic complex derived from dimethyl-bis]self-organized dimer, 67 [211]. The tin-fluorine bonds ]2.82 and 2.74 A) are longer than normal covalent bonds and this was assigned to the weak nucleophilic character of the tetrafluoroborate anion. Perhaps this is another example of tin-fluorine secondary bonds. 

The assigned peaks (001, 002, 003, and 005) indicated that the structure is mainly characterized by a lamellar periodicity in one direction. The intense peak with a distance of 35.1 A can be assigned to the length of the organic dimer. It was transcribed into the organosilica material upon sol-gd condensation of the terminal hydrolyzable trialkoxysilyl functional groups as evidenced by liquid- and solid-state NMR spectroscopy and X-ray diffraction studies [57,58]. 

Enthalpies are referred to the ideal vapor. The enthalpy of the real vapor is found from zero-pressure heat capacities and from the virial equation of state for non-associated species or, for vapors containing highly dimerized vapors (e.g. organic acids), from the chemical theory of vapor imperfections, as discussed in Chapter 3. For pure components, liquid-phase enthalpies (relative to the ideal vapor) are found from differentiation of the zero-pressure standard-state fugacities these, in turn, are determined from vapor-pressure data, from vapor-phase corrections and liquid-phase densities. If good experimental data are used to determine the standard-state fugacity, the derivative gives enthalpies of liquids to nearly the same precision as that obtained with calorimetric data, and provides reliable heats of vaporization. 

VPLQFT is a computer program for correlating binary vapor-liquid equilibrium (VLE) data at low to moderate pressures. For such binary mixtures, the truncated virial equation of state is used to correct for vapor-phase nonidealities, except for mixtures containing organic acids where the "chemical" theory is used. The Hayden-0 Connell (1975) correlation gives either the second virial coefficients or the dimerization equilibrium constants, as required. 

If the mixture includes organic acids, the equations of Hayden and O Connell yield equilibrium constants for all possible dimerization reactions. 

Acryhc esters dimerize to give the 2-methylene glutaric acid esters catalyzed by tertiary organic phosphines (37) or organic phosphorous triamides, phosphonous diamides, or phosphinous amides (38). Yields of 75—80% dimer, together with 15—20% trimer, are obtained. Reaction conditions can be varied to obtain high yields of trimer, tetramer, and other polymers. 

The extract is vacuum-distilled ia the solvent recovery column, which is operated at low bottom temperatures to minimise the formation of polymer and dimer and is designed to provide acryUc acid-free overheads for recycle as the extraction solvent. A small aqueous phase in the overheads is mixed with the raffinate from the extraction step. This aqueous material is stripped before disposal both to recover extraction solvent values and minimise waste organic disposal loads. 

In the organic phase the monomer is in equiUbrium with the dimer ... 

The methodology for preparation of hydrocarbon-soluble, dilithium initiators is generally based on the reaction of an aromatic divinyl precursor with two moles of butyUithium. Unfortunately, because of the tendency of organ olithium chain ends in hydrocarbon solution to associate and form electron-deficient dimeric, tetrameric, or hexameric aggregates (see Table 2) (33,38,44,67), attempts to prepare dilithium initiators in hydrocarbon media have generally resulted in the formation of insoluble, three-dimensionally associated species (34,66,68—72). These precipitates are not effective initiators because of their heterogeneous initiation reactions with monomers which tend to result in broader molecular weight distributions > 1.1)... 

Commercial polystyrenes are normally rather pure polymers. The amount of styrene, ethylbenzene, styrene dimers and trimers, and other hydrocarbons is minimized by effective devolatilization or by the use of chemical initiators (33). Polystyrenes with low overall volatiles content have relatively high heat-deformation temperatures. The very low content of monomer and other solvents, eg, ethylbenzene, in PS is desirable in the packaging of food. The negligible level of extraction of organic materials from PS is of cmcial importance in this appHcation. 

Addition compounds form with those organics that contain a donor atom, eg, ketonic oxygen, nitrogen, and sulfur. Thus, adducts form with amides, amines, and A/-heterocycles, as well as acid chlorides and ethers. Addition compounds also form with a number of inorganic compounds, eg, POCl (6,120). In many cases, the addition compounds are dimeric, eg, with ethyl acetate, in titanium tetrachloride-rich systems. By using ammonia, a series of amidodichlorides, Ti(NH2) Cl4, is formed (133). 

The trans isomer is more reactive than the cis isomer ia 1,2-addition reactions (5). The cis and trans isomers also undergo ben2yne, C H, cycloaddition (6). The isomers dimerize to tetrachlorobutene ia the presence of organic peroxides. Photolysis of each isomer produces a different excited state (7,8). Oxidation of 1,2-dichloroethylene ia the presence of a free-radical iaitiator or concentrated sulfuric acid produces the corresponding epoxide [60336-63-2] which then rearranges to form chloroacetyl chloride [79-04-9] (9). 

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