In dimerization

Aluminium also has a strong tendency to achieve a noble gas configuration by electron pair acceptance as shown in dimeric aluminium chloride. 

Anhydrous aluminum bromide, AIBr., forms colorless trigonal crystals and exists in dimeric form, in the crystal and Hquid phases (1). Dissociation... 

The electron-rich carbon—carbon double bond reacts with reagents that are deficient in electrons, eg, with electrophilic reagents in electrophilic addition (6,7), free radicals in free-radical addition (8,9), and under acidic conditions with another butylene (cation) in dimerization. 

The photolysis of azirines has been shown to result in dimerization to pyrazines (72JA1395) and although this formally corresponds to a type B synthesis it involves an isolable intermediate (105) and does not proceed by simple dimerization (Scheme 70). 

In dimers composed of equal molecules the dimer components can replace each other through tunneling. This effect has been discovered by Dyke et al. [1972] as interconversion splitting of rotational levels of (HF)2 in molecular beam electric resonance spectra. This dimer has been studied in many papers by microwave and far infrared tunable difference-frequency laser spectroscopy (see review papers by Truhlar [1990] and by Quack and Suhm [1991]). The dimer consists of two inequivalent HE molecules, the H atom of one of them participating in the hydrogen bond between the fluorine atoms (fig. 60). PES is a function of six variables indicated in this figure. 

E. V. Albano. Irreversible saturation transitions in dimer-dimer reaction models of heterogeneous catalysis. J Phys A (Math Gen) 25 2557-2568, 1992 Corrigendum. J Phys A (Math Gen) 26.3661, 1993. 

A. Maltz, E. V. Albano. Kinetic phase transitions in dimer-dimer surface reaction models studied by means of mean-field and Monte Carlo methods. Surf Sci 277-A A-42S, 1992. 

In contrast with 69, molecules of benzotelluradiazole 75 in the solid state are associated in dimers rather than polymeric chains. The bulky t-butyl groups of 75 prevent a higher degree of association and provide for good solubility of 75, which readily crystallizes from its pentane solution. 

In dimerization and oligomerization reactions, ionic liquids have already proven to be a highly promising solvent class for the transfer of established catalytic systems into biphasic catalysis. 

Iron in the oxidation state + III in dimeric p-oxo compounds 5 can be reduced to iron + II, leading to monomeric phthalocyanines 6.351... 

For neutral radicals, the most significant term in eq. (144) is that which is first order in the overlap. This term contains expansion coefficients of directly interacting positions where in dimerization a new a bond is formed. The higher the values of these expansion coefficients, the larger is the interaction energy, in accord with chemical anticipation for dimerization to occur in positions of the highest spin densities. With radical ions, also, the last terms in eqs. (143) and (144) are important, since they stand for coidombic interactions. 

Figure 39-15. The leucine zipper motif. A shows a helical wheel analysis of a carboxyl terminal portion of the DNA binding protein C/EBP. The amino acid sequence is displayed end-to-end down the axis of a schematic a-helix. The helical wheel consists of seven spokes that correspond to the seven amino acids that comprise every two turns of the a-helix. Note that leucine residues (L) occur at every seventh position. Other proteins with "leucine zippers" have a similar helical wheel pattern. B is a schematic model of the DNA binding domain of C/EBP. Two identical C/EBP polypeptide chains are held in dimer formation by the leucine zipper domain of each polypeptide (denoted by the rectangles and attached ovals). This association is apparently required to hold the DNA binding domains of each polypeptide (the shaded rectangles) in the proper conformation for DNA binding. (Courtesy ofS McKnight)...

A V(III)-Cr(in) dimer has been detected as an intermediate in the V(IV) + Cr(II) reaction and its formation and subsequent decomposition studied. Since V(IV) was arranged to be in excess of Cr ", no complications ensued from the latter ion bringing about further reduction of V(III) to V(II). Under these conditions the overall reaction corresponds accurately to... 

Pyykkd, P. and Mendizabal, F. (1997) Theory of the d -d ° closed-shell attraction. II. Long-distance behaviour and non-additive effects in dimers and trimers of type (X-Au-L)n (X=C1,1, H L=-PH3, PMe3, -NCH). Chemistry - A European Journal, 3, 1458-1465. 

In step 1, only minor changes in time and temperature were made. In step 2, it was found that the addition of diethylamine led to a decrease in dimeric byproducts. An improved ratio of the intermediate (with the iodide moiety para rather than ortho to the methoxy group) was attained with a reagent far less expensive than the silver acetate used in the preliminary synthetic route. 

As with 2-cyclopentenone, the ratio (70) (71) varies with the molar concentration of the enone, the head-to-head dimer (71) becoming increasingly important at higher concentrations/133 This reaction is efficiently sensitized by acetophenone, benzophenone, thioxanthone, and naphthalene. The same enone concentration effect was observed in the sensitized photo-dimerization as in the direct photolysis. Similarly, quenching of the dimerization by piperylene was not accompanied by a change in dimer ratio. Systematic... 

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