Transition formation

Photochromism in solution and in the solid state can be the result oi intramolecular changes, e.g. tautomerism, ring opening, cis-trans isomerization, free radical formation, stereoisomenc transition, formation of dimers nd such similar reversible reactions. Some examples are given below ... 

In connection with this, an unusual isomerization of the propargyl chiral centre in 89 was observed during a PKR in which 90 was obtained as an only isomer. This result shows the transition formation of positive charges at the propargylic position during the cycloaddition (Scheme 26) [123]. 

One drop of dilute silver nitrate has to be added to speed up the reaction. Silver ions act as catalysts the catalytic action is due to the transitional formation of silver(III), Ag3+. Halides must be absent they can be removed easily by evaporating the solution with concentrated sulphuric acid until fumes of sulphur trioxide appear. After cooling, the solution can be diluted and the test carried out. The excess of peroxodisulphate can be decomposed by boiling ... 

The catalytic action of silver is due to the transitional formation of silver(II), Ag2+, and/or silver(III), Ag3+, ions, which, as powerful oxidants, oxidize manganese(II) to permanganate. 

Hypophosphorous acid-starch solution test Iodates are reduced by hypo-phosphorous acid eventually to iodides. The reaction takes place in three stages (with the transitional formation of phosphorous acid) ... 

Irradiation of the matrix (420-500 nm, a range not corresponding to the pimer charge-transfer transition) produced an additional triplet (ti j 10 hours) with D = 0.0175 cm and E = O, r = 5.4 A. Careful examination of the spectra of concentrated solutions of 4 revealed absorption in the range of 420-500 nm Thin film spectroscopy of 4 revealed that covalent dimers (rather than singlet pairs) gave rise to the new triplet via a no ncr transition Formation of a triplet [D = 0.0146 cm" and E = O, r = 5.5 A] from the dimer of 2 , 2-2, has been accomplished by irradiation in an MTHF glass. The equilibria describe the relationship of the triplets and radicals in Eq. 13. The two triplet pairs (A and B) are not readily interconvertible. 

Reversibility of the phase transitions formation of metastable phases... 

The first report of the existence of fullerenes in 1985 [1], and the subsquent discovery in 1990 of a method to produce them in macroscopic amounts [2], paved the way to a new era of carbon science that involves curved surfaces on the nanoscopic scale. As is well known, the aggregation of fuUerene molecules at moderate temperatures and pressures leads to molecular sohds termed ful-lerites. The (buckminsterfuUerene) and Cyg fullerenes and the corresponding fullerites are the easiest to produce, and for this reason they have been the subject of most experimental works. Certain aspects of the solid-state science of fullerenes (e.g., crystal structures, phase transitions, formation of exo- and... 

Nitroxide 108a reacts in its mesomeric form 108b and is destroyed in a weak acid environment into a mixture of the parent 16b and nitrone 109 [101]. Using a low concentration of ROO, 16b was transformed into the dimer 103 as the main product. QI 104 and 105 were present only in small amounts [106]. The amount of QI increased with the concentration of ROO present in the system. Compounds 103-105 were also detected in autoxidized squalene doped with 16b. This confirms the transformation pathway of 16b based on transitional formation of aminyls 102. It should be noted that QI 104 and 105 were also identified as metabolites of 16b in rats [101]. This indicates a paralelism of processes involving 16b in vivo and in vitro. 

Styrene ether modified fatty acids (DVB) Hexagonal No phase transition Formation of non-dissolvable gels [65]... 

The synthesis of symmetric 1-aryl 5-arylaminotetrazoles 230 was initially performed by reacting symmetrical diarylthioureas 229 with sodium azide in the presence of lead carbonate or lead oxide. The reaction proceeds via the transitional formation of a diarylcarbodiimide that readily reacts with the azide ion to give the l-aryl-5-arylaminotetrazole 230 (Scheme 44A) [166-168]. Percival and co-workers extended this method to the synthesis of a group of symmetrical l-alkyl-5-alkylaminotetrazoles 233 that were prepared from the appropriate symmetric carbodiimides 232 in benzene or toluene with hydrazoic acid (Scheme 44B) [156]. The carbodiimides 232 were generated in a previous step from symmetrical dialkylthioureas 231 in the presence of mercuric oxide. 

A stage is a typical active object. A stage is activated by receiving a hardware task, and its behavior requires plural machine cycles. Therefore, its behavior is defined in state-transition format. All actions in one state of each stage are performed simultaneously in the same cycle. A stage stays active until it terminates or transfers its task to another stage. 

STUDIES ON THE TRANSITIONAL FORMATION AND MOLECULAR INTERACTIONS OF A POLYELECTROLYTE... 

---