Solvent intramolecular

The NMR spectra of some 1- and 2-substituted perimidinium salts 139 are discussed and assigned. Several 2-substituted derivatives possess and H NMR spectra that reflect relatively slow prototropic tautomerism due to hydrogen bonding with a solvent, intramolecular hydrogen bonding, or enhanced delocalization of the nitrogen lone pair (88MRC191). 

The conformation of a polymer in solution is the consequence of a competition between solute intra- and intermolecular forces, solvent intramolecular forces, and solute-solvent intermolecular forces. Addition of a good solvent to a dry polymer causes polymer swelling and disaggregation as solvent molecules adsorb to sites which had previously been occupied by polymer intra- and intermolecular interaction. As swelling proceeds, individual chains are brought into bulk solution until an equilibrium solubility is attained. 

Murphrey, T. H. and Rossky, P. J. The role of solvent intramolecular modes in excess electron solvation dynamics, J.ChemPhys., 99 (1993). 515-522... 

Anionic polymerization Initiated by electron transfer (e.g., sodium-naphthalene and styrene In THF) usually produces two-ended living polymers. Such species belong to a class of compounds called bolaform electrolytes (27) In which two Ions or Ion pairs are linked together by a chain of atoms. Depending on chain length, counterion end solvent, Intramolecular Ionic Interactions can occur which in turn may affect the dissociation of the ion pairs Into free ions or the llgand-lon pair complex formation constants. 

Sammes and his group (77JCS(P1)663 78JCS(P1)1293 81JCS(P1)1909) attempted the thermal intramolecular cycloaddition of the substituted pyrimidine 507 possessing an alkyne to produce a monoterpene alkaloid ( )-actinidine (511)(Scheme 64). Upon thermolysis of the pyrimidine 507 at 200°C in a sealed tube, using dimethylformamide as solvent, intramolecular cycloaddition led to the known pyridone 509 in 87% yield by the loss of the amide bridge from intermediate 508. Conversion of the pyridone 509 into the chloropyridine followed by reductive dechlorination afforded racemic actinidine 511. 

Intramolecular proton transfer is an Important mechanism of excited state deactivation. It is, however, only partially understood at present especially the role of the triplet states is still unknown. This is due to the fact that phosphorescence has never been observed except in hydrogen-bond-breaking solvents. Intramolecular proton transfer is of practical Importance in the field of stabilizers, optical brlghteners, photochromic substances, and dyes. 

When o-azidobenzoic acid and its potassium salt were photolysed in H2O, EtOH, THE, EtOH-H20 or THF-H2O, the major product was 2,1-benzisoxazo-lone, from intramolecular cyclization. Varying amounts of azepine products were observed, depending on the solvent. Intramolecular nitrene cyclization was also observed in the photolysis of the azido-functionalized cryptand (43), which afforded the benzopyrazole (44) after an aerobic workup. ... 

In the case of the oxidation of indole derivatives, nucleophilic attack by solvent may occur (eq 30). Reserpine undergoes an analogous alkoxylation. In the absence of a nucleophilic solvent, intramolecular cyclization occurs, an example of which is illustrated in the total synthesis of sporidesmin A (eq 31). ... 

Numerical simulations have also been instrumental in elucidating the differences between simple and complex solvents in the way they dynamically respond to a newly created charge distribution. The importance of translational motions that change the composition or structure near the solute, the consequent early failure of linear response theory in such systems, and the possible involvement of solvent intramolecular motions in the solvation process were discovered in this way. 

Many heterocycles containing two or more heteroatoms can exist in more than one tautomeric form. Both external (polarity of the solvent, intramolecular hydrogen bonding) and internal (relative resonance stabilization of the conjugated system, stabilities of the functionalities) factors influence such tautomeric equilibria. For five- and six-membered rings, frequently more than one tautomer preserves the aromatic character. Comparisons of tautomeric equi-... 

The nucleophile is often used in large excess and, especially in the case of simple nucleophiles such as methanol and ethanol, is often used as the solvent. Nevertheless, efficient acylation reactions can be achieved with much smaller quantities of the nucleophile in an inert solvent. Intramolecular reactions are particularly useful to prepare both lactams (Scheme 4.22) and lactones (Schemes 4.23 and 4.24). The carbonylation... 

In dilute solution, the properties of the polymer are characterized by the interaction between the solvent and the polymer. In a good solvent, the polymer appears swollen and occupies a large volume. In this scenario, intermolecular forces between the solvent and monomer subunits dominate over intramolecular interactions. In a bad solvent or poor solvent, intramolecular forces dominate and the chain contracts. In the theta solvent, or the state of the polymer solution where the value of the second virial coefficient becomes 0, the intermolecular polymer-solvent repulsion balances exactly the intramolecular monomer-monomer attraction. Under the theta condition (also called the Flory condition), the polymer behaves like an ideal random coil. 

Irradiation of cyclohexenone 32 with the tertiary a-silylamine EtjNCHjSiMej in methanol solution in the presence of the electron acceptor 9,10-dicyanoanthracene (DCA) yields predominantly the desi-lylated adduct 32b. The product ratios depend on amine concentration. " The mechanism proposed for adduct formation is outlined in Scheme 24. Oxidation of the tertiary amine by singlet DCA yields the amine cation radical, which undergoes desilylation upon nucleophilic reaction with the solvent. Addition of the a-aminoalkyl radical to the neutral enone affords the radical adduct, which is reduced by DCA and protonated by solvent. " Intramolecular trapping of the radical adduct can compete with reduction by DCA"-, as seen in the reaction of 32 with an a-silylanihne, which yields the tandem addition product 32c (Scheme 24). ... 

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