Spectroscopy electrophilic substitution reaction

The existence of different types of ion pairs, namely so called intimate or contact ion pairs and solvent-separated ion pairs was originally postulated in order to explain the stereochemical course of solvolysis and electrophilic substitution reactions [52—55). Since then the existence of both types of ion pairs has been widely accepted and found to be in agreement with results obtained by various physico-chemical methods, such as UV spectroscopy, conductivity measurements and electron spin resonance (56—62). In "contact ion pairs , cations and anions are considered to be in immediate contact with each other, while in solvent-separated ion pairs, ions are separated by solvent molecules. 

Neutral Complexes. Interaction of acetylacetone and hydrous Rh2G3 gives the trisacetylacetonate, which has been resolved into enantiomeric forms. It undergoes a variety of electrophilic substitution reactions of the coordinated ligand, such as chlorination. The stereochemistry and racem-ization of the cis- and trans-isomers of the unsymmetrical trifluoroacetyl-acetonate have been studied by nmr spectroscopy the compound is extremely stable to isomerization. 

There have also been reports of preparation of fluoroimidazoles by electrophilic fluorination of metalated intermediates, although results have been modest. There exists an unpublished report that a more than 50% yield of 2-fluoro-1 -methylimidazole was produced by reaction of 2-lithio-1 -methylimidazole with perchloryl fluoride. "in an another attempt to prepare fluoroimidazoles by electrophilic substitution, reaction of l-methyl-2-trimethylstannylimidazole, l-methyl-4-trimethylstannylimidazole, or l,2-dimethyl-5-trimethylstannylimidazole with dilute fluorine gas at —78°C gave crude product mixtures that contained the corresponding fluorinated imidazole as detected by NMR spectroscopy. The products were not isolated. "... 

Thiazolin-5-one, 2-alkoxy-4-arylazo-rearrangements, 5, 777 2-Thiazolin-5-one, 4-methyl-2-phenyl-protomeric equilibrium, 6, 249 4-Thiazolin-2-one, 4-aryl-reactions, 6, 286 4-Thiazolin-2-one, 3,4-dimethyl-protonation, 6, 286 4-Thiazolin-2-one, 4-methyl-reactions, 6, 286 Thiazolinones electrophilic attack, 5, 99 Thiazolin-2-ones IR spectroscopy, 6, 241 nucleophilic displacement, 5, 100 2-Thiazolin-4-ones reactions, 6, 287 2-substituted synthesis, 6, 306 synthesis, 5, 129 6, 309, 310 tautomerism, 6, 248 2-Thiazolin-5-ones IR spectroscopy, 6, 242 reactions, 6, 288 synthesis, 5, 138 tautomerism, 6, 249 4-Thiazolin-2-ones synthesis, 6, 314 4-Thiazolin-3-ylacetic acid esters... 

In Part 11 we concentrate on aromatic systems, starting with the basics of structure and properties of benzene and then moving on to related ciromatic compounds. We even throw in a section of spectroscopy of aromatic compounds. Chapters 7 and 8 finish up this pcirt by going into detail about substitution reactions of aromatic compounds. You find out all you ever wanted to know (and maybe more) about electrophilic and nucleophilic substitutions, along with a little about elimination reactions. 

These compounds undergo retrocycloaddition (8) on heating in inert solvents, and are subject to fragmentation on irradiation at 254 nm as well. Both are high-yield processes, easily monitored by NMR spectroscopy. The released metaphosphates are routinely trapped by the addition reaction with alcohols or amines, or by electrophilic substitution on the pyrrole ring. In some cases, trapping has been accomplished by reaction with the OH groups on the surface of suspended silica gel... 

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