Reactivity Ratios and Sequence Distribution Characterization by Quantitative 13C NMR for RAFT Synthesis of Styrene‐Acrylonitrile Copolymers

The kinetics and reactivity ratios of styrene‐acrylonitrile (SA) copolymerization have been studied extensively in bulk and in a variety of solution media using conventional free radical polymerizations (FRPs). Due to the significant difference in the two reactivity ratios for this monomer pair, at certain feed ratios the copolymers display composition drift with conversion due to monomer depletion. In this study, the kinetics of SA copolymerization using Reversible Addition‐Fragmentation Chain Transfer (RAFT) has been studied in bulk at 80 °C. The reactivity ratios for the terminal model were calculated from the comonomer sequence distributions for the RAFT process at low conversion for nine different compositions and found to be in the same range as those reported for conventional FRP of SA. The changes in the composition and sequence distribution with conversion were studied for three feed compositions. The copolymers show compositional drift with conversion, except at the azeotropic composition, and match the predictions from the reactivity ratios obtained at low conversion. From quantitative ¹³C NMR the triad distributions of these copolymers were estimated and found to match the predicted triad distributions as conversion increased. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 919–927     

Calixarenes as Polyhapto-aromatic Ligands: Alkali Metal Ions and Sulfonated Calixarenes

Crystal structure determinations for the hexarubidium and octacesium derivatives of calix[6]arene hexasulfonic acid, as well as of a new solvate of the pentasodium derivative of calix[4]arene tetrasulfonic acid, and comparison with structural data from the literature for alkali metal complexes of sulfonated calixarenes, have provided further evidence for the importance of interactions with aromatic ~ -electrons for the heavier alkali metal cations. There is evidence as well that this interaction can be enhanced by extended ionization of the sulfonated calixarene.     

Octahedral CuII and NiII complexes manifesting with N′-[1-(pyridin-2-yl)ethylidene] acetohydrazide: Structural outlooks and spectral characteristics

A tridentate hydrazone precursor, N′-[1-(pyridin-2-yl)ethylidene]acetohydrazide (L) (1:1 refluxed product of acetichydrazide and 2-acetylpyridine), produced two octahedral Cu^II and Ni^II derivatives, [CuL₂]·NO₃ (1) and [NiL₂]·ClO₄·H₂O (2). Both are subjected to X-ray diffraction system, and structural investigation shows that the central metal atom (Cu^II or Ni^II) adopts a distorted octahedral geometry with N₄O₂ donor sets by coordination of a pair of independent hydrazone precursors. Besides X-ray study, IR and UV-vis spectra, thermal analysis and room temperature magnetic moments are utilized for establishing significant characteristics of both complexes. It is apparent that the M-N_pyridine bonds are slightly longer than the M-N_imino bonds, Cu1-N1 and Cu1-N4 [2.300(2) and 2.038(2) ?] for 1 and Ni1-N1 and Ni1-N4 [2.075(2) and 2.084(1) ?] for 2, Cu1-N2 and Cu1-N5 [2.062(1) and 1.932(1) ?] for 1 and Ni1-N2 and Ni1-N5 [2.008(2) and 1.975(2) ?] for 2, respectively. As per our observation, the effective magnetic moment value (μ_eff) is found to be 1.77 B.M. for 1 and 3.06 BM for 2, respectively.     

Regioselective A-Ring Chlorination of Benzodiazepine Analogues Using tert-Butyl Hypochlorite

Treatment of 2-phenyl-2,3-dihydro-1,4-benzodiazepin-5(4H)-one and a series of 1,4-benzoxazepinone analogues with tert-butyl hypochlorite affords products shown, by NMR and MS spectroscopy, to be chlorinated exclusively in the A-ring at positions 7 and/or 9.     

An Improved Large Scale Synthesis of 2-Amino-4-chloropyridine and Its Use for the Convenient Preparation of Various Polychlorinated 2-Aminopyridines

An efficient large scale synthesis of 2-amino-4-chloropyridine (3) has been achieved through a modification of existing literature procedures. Compound 3 was used to prepare the previously unreported 2-amino-4,5-dichloropyridine (4). The known 2-amino-3,4-dichloropyridine (5) and 2-amino-3,4,5-trichloropyridine (6) were prepared from 3 by new routes and in higher yields than previously reported.