Conglomerate complexe

As typical examples of crystal-to-crystal thermal reactions, the cyclization of allene derivatives to four-membered ring compounds and the transformation of a racemic complex into a conglomerate complex are described. 

The rac-inclusion complex 79 consisting of 12 and Me4NCl 80 in a 1 1 ratio was easily converted into conglomerate complex 81 by heating or by contact with MeOH vapors in the solid state [42], Firstly, authentic samples of 79 and 81 were prepared by the following method. When 12 (1.43 g) and 80 (0.55 g) was recrystallized from 7 and 15 ml of MeOH, rac-79 and conglomerate 1 1 complex 81 were obtained, respectively. 

Furthermore, the much simpler achiral ammonium salt tetramethylammonium chloride (112) was found to be useful for the enanhomeric separahon of 10a, although 112 forms both racemic and conglomerate complexes with 10a and 10b (or 10c), respechvely. Firshy, the racemic and conglomerate complexes of 10 and 112... 

Study of the enantiomeric separation of 10a by complexation with 112 revealed two interesting modes of transformation of racemic complex 113 into conglomerate complex 114 in the solid state. One is a thermal transformation. Thermogravi-metric and differential thermal analysis measurements of 113 showed the evaporation of MeOH at 120°C, phase transfer from MeOH free-113 to 114 at 183 C and... 

The substation provides a monitoring point for system operating parameters. The power system is a highly complex and sensitive conglomeration of parts that must all be coordinated to function properly. For this reason, the operating conditions must be veiy closely obsci vcd and controlled. This is done by using specialized sensors to acquire the intormation and then cominunication systems to convey the information to a central point. For immediate response to system faults (such as damaged conduc-... 

It is well known that spontaneous resolution of a racemate may occur upon crystallization if a chiral molecule crystallizes as a conglomerate. With regard to sulphoxides, this phenomenon was observed for the first time in the case of methyl p-tolyl sulphoxide269. The optical rotation of a partially resolved sulphoxide (via /J-cyclodextrin inclusion complexes) was found to increase from [a]589 = + 11.5° (e.e. 8.1%) to [a]589 = +100.8 (e.e. 71.5%) after four fractional crystallizations from light petroleum ether. Later on, few optically active ketosulphoxides of low optical purity were converted into the pure enantiomers by fractional crystallization from ethyl ether-hexane270. This resolution by crystallization was also successful for racemic benzyl p-tolyl sulphoxide and t-butyl phenyl sulphoxide271. 

The first resolution of an octahedral complex into its enantiomers was achieved in 1911 by A. Werner, who got the Nobel Prize in 1913, with the complex [Co(ethylenediamine)(Cl)(NH3)] [10]. Obviously, resolution is to be considered only in the case of kinetically inert complexes whose enantiomers do not racemize quickly after separation. This is a very important remark since, as noted above, the interesting complexes are those containing exchangeable sites required for catalytic activity and thus more sensitive to racemization. We will not discuss here the very rare cases of spontaneous resolution during which a racemic mixture of complexes forms a conglomerate (the A and A enantiomers crystallize in separate crystals) [11,12]. 

Racemic Crystal-to-Conglomerate Crystal Transformation Reactions in 2,2 -Dihydroxy-1,1 -binaphthyl-l /le4N+CI Complex... 

At higher threshold fields, the banana leaf and most other B7 textures observed for MHOBOW also convert irreversibly to bistable blue, though the picture is still complex, with unusual textures still seen in the cell. Our interpretation of this behavior, however, is simple. The bistable blue texture observed for MHOBOW is obtained from an SmCsPF conglomerate the target of the molecular design and synthesis effort. 

It is worth to mention that both coordination compounds, namely [Ca(7)2]DBTA and [Ca(H20)](12)DBTA form conglomerates with their enantiomers, respectively. Thus, optical resolution of racemic DBTA by preferential crystallization of these coordination complexes is also possible. [26, 27]... 

To date, the composition of the intestinal microflora still remains to be definitively described. However, it seems quite clear that it consists of a complex, symbiotic conglomerate of more than 500 different, predominantly anaerobic, strains. The enzymatic equipment of this symbiotically living colon microflora was adapted predominantly because of the changing types of food that were available during the course of evolution [36],... 

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