Reference

Kinetics and mechanism of cationic polymerization of 5-methyl-2-oxazoline

Kinetics and mechanism of cationic polymerization of 5-methyl-2-oxazoline. Concurrent propagation through ionic and covalent species with methyl iodide initiator. Kobayashi, Shiro; Morikawa, Kenji; Shimizu, Naoki; Saegusa, Takeo (Fac. Eng., Kyoto Univ., Kyoto 606, Japan). Polym. Bull. (Berlin), 11(3), 253-60 (English) 1984. CODEN: POBUDR.There are some reagents with their cas registry numbers 89784-65-6 and 74-88-4 are used in this study. ISSN: 0170-0839. DOCUMENT TYPE: Journal CA Section: 35 (Chemistry of Synthetic High Polymers) Section cross-reference(s): 22 Kinetic anal. of the cationic polymn. of 5-methyl-2-oxazoline (I) [30059-45-1] was performed with Me tosylate (II) [80-48-8] and MeI [74-88-4] initiators by using 1H NMR spectroscopy. With II, the polymn. of I proceeded through oxazolinium tosylate species, and the rate const. of propagation was detd. With MeI, on the other hand, the propagating ends were present in equil. with alkyl iodide (covalent) species and oxazolinium (ionic) species. Two model reactions were used to det. equil. consts. and to evaluate the reactivity of covalent and ionic species. One of the ionic species and one of the covalent species were considered to propagate concurrently and contribute to the whole propagation at comparative extents. .

Steric effects in SN2 reactions

Steric effects in SN2 reactions. Determination of transition state structures for the quaternization of 2-alkylpyridines and -thiazoles by a combined experimental and molecular mechanics procedure. Berg, Ulf; Gallo, Roger (Chem. Cent., Univ. Lund, Lund S-220 07, Swed.). Acta Chem. Scand.Some commonly used reagents like 3581-87-1 and 80-48-8 are used in this experiment., Ser. B, B37(8), 661-73 (English) 1983. CODEN: ACBOCV. ISSN: 0302-4369. DOCUMENT TYPE: Journal CA Section: 22 (Physical Organic Chemistry) SN2 transition-state structures for the Menschutkin reactions between 2-alkylpyridines or -thiazoles and MeX (X = I, and SO3F) are calcd. by the Allinger 1973 force field method. Exptl. found differences in steric energies between the quaternary iminium ions and the activated complexes are used as measures for the elevation of the position of the transition state. Ests. of the C-N distance (rC-N) in the transition state result in a 22±4% extension compared to the ground state value (1.48 ?), depending upon the transition state model used. The preferred model results in rC-N = 1.812±0.013 ?. Consistent results were obtained with nucleophiles of different geometries (pyridines and thiazoles). A change of leaving group from iodide to fluorosulfonate leads to an extension of rC-N by 0.04±0.02 ?. .