Spectroscopy nucleophilic displacement

Cellulose, Polysaccharide, Activation, Cellulose solvents. Esterification, Etherification, Ionic liquids, NMR spectroscopy. Nucleophile displacement. Protecting groups, Regioselective functionalization... 

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... 

A variety of studies on nucleophilic displacement reactions have been carried out in the gas phase, utilizing pulsed ion cyclotron resonance (ICR) spectroscopy. Many of these reactions occur with conveniently measurable efficiencies... 

With an E° value of —0.75 V, entry no. 19 of Table 17, reaction between alkyl halides and alkyllithium compounds, represents a strongly exergonic electron-transfer reaction which is expected to proceed at a diffusion-controlled tate. Experimental rate constants are not available, but such reactions are qualitatively known to be very fast. As we proceed to entry no. 21, two model cases of the nucleophilic displacement mechanism, it can first be noted that the nosylate/[nosylate]- couple is electrochemically reversible the radical anion can be generated cathodically and is easily detected by esr spectroscopy (Maki and Geske, 1961). Hence its E° = —0.61 V is a reasonably accurate value. E° (PhS /PhS-) is known with considerably less accuracy since it refers to an electrochemically irreversible process (Dessy et al., 1966). The calculated rate constant is therefore subject to considerable uncertainty and it cannot at present be decided whether the Marcus theory is compatible with this type of electron-transfer step. In the absence of quantitative experimental data, the same applies to entry no. 22 of Table 17. For the PhS-/BuBr reaction we again suffer from the inaccuracy of E° (PhS /PhS-) what can be concluded is that for an electron-transfer step to be feasible the higher E° value (—0.74 V) should be the preferred one. The reality of an electron-transfer mechanism has certainly been strongly disputed, however (Kornblum, 1975). 

The reaction proceeds with total regio- and diastereoselectivity, as shown by H-NMR spectroscopy. /J-Iodo isocyanates are generally unstable, their purification is difficult and it is convenient to convert them into more stable derivatives. /Hodo carbamates were readily and stereose-lectively prepared by warming the isocyanate with an appropriate alcohol and successive thermal nucleophilic displacement yielding 2-oxazolidinones, e.g., 19 - 20 (see Table 3). Furthermore, when trans-iodo isocyanates were treated with an alcohol in basic medium, the carbamates form first and were immediately converted into the corresponding aziridines, e.g, 19 -> 21. 

In one instance, the proton sponge derivatives 61 were prepared by nucleophilic displacement of the activated chlorine atoms in pen-dichloroacenaphthene 60 on heating with excess of dimethyl- or diethylamine (equation 2)53. Regrettably, the structure of all compounds reported in this work was elucidated without NMR analysis, utilizing only combustion analysis and IR spectroscopy. 

Polymerization of these bisdichloromaleimides was carried by nucleophilic displacement of chlorine with 9,9-bis(p-aminophenyl)fluorene. The resulting polymers were characterized by IR spectroscopy and reduced viscosity measurements. Anaerobic char yields of these polymers at 800°C ranged from 55-60%. In presence of air, a complete loss of weight was observed between 600-650 C. Thermal cross-linking of these polymers was also investigated. 

The reactions of McjSn with c -4-t-butylcyclohexyl bromide and with rra/w-4-t-butylcyclohexyl tosylate have been shown by H nmr spectroscopy to give the same product, and on the basis of independent evidence this product has been assigned the cir-configuration as shown in Scheme 7. Thus the reaction of the tosylate occurs by a nucleophilic displacement reaction with inversion of configuration at the carbon centre, and the bromide reaction apparently proceeds with retention (Koermer et al., 1972). 

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