Electron spin resonance studies of spin-labeled polymers. IV. Slow-motional effects in solid polystyrene

Shape changes in the electron spin resonance spectrum of spin-labeled polystyrene have been studied as a function of temperature in the range 77–340°K. Rotational correlation times have been calculated by using recent theories of slow-motional effects on ESR spectra. Three models were used, namely, Brownian, moderate jump diffusion, and large jump diffusion. The moderate jump model gave correlation times in good accord with those found by other techniques for the δ relaxation in polystyrene. The relaxation was found to be independent of molecular weight.     

Two novel cassane diterpenoids from Acacia jacquemontii

The structure of two new diterpenoids (1 and 3), both of which contain the unique feature of a 7-membered hemiacetal ring B, have been established from chemical and spectroscopic (especially NMR) evidence. Single crystal X-ray crystallographic analysis of 1 has confirmed the structure and allowed the relative stereochemistry to be determined.     

Formation of aryl benzanthrones from anthraquinone-catalysed degradation of lignin

Anthraquinone-catalysed pulping of $\text{Pinus}$$\text{radiata}$ gives the aryl benzanthrones (1) and (2), their formation involving reaction between anthraquinone and lignin constituents of the wood.     

Convenient preparation and full characterization of a synthetically useful salt of the dithianitronium cation, SNSSbF6, from readily available starting materials

The synthetically useful SNSSbF6 is prepared, in good yield, from the reactions of S3N2Cl2 or S3N3Cl3 with stoichiometric amounts of AgSbF6 and S8 in liquid SO2. SNSSbF6 crystallizes monoclinic in space group C2/m (a = 9.740(2) A, b = 6.644(2) A, c = 5.334(1) A, beta = 90.58(2) degrees , Z = 2). The crystal structure was determined by standard methods and refined to R1 = 0.019 and wR2 = 0.048. The structure consists of discrete linear centrosymmetric SNS+ cations [S-N = 1.4871(10) A] and almost octahedral SbF6- anions, with weak cation-anion interactions. The lattice energy of SNSSbF6 was determined from the volume-based method as 525 +/- 32 KJ mol(-1) and the heat of formation of SNSSbF(6(s)) has been estimated as -1566 +/- 24 KJ mol(-1). The FT-IR, Raman, and (14)N NMR spectra are reported, as well as an in situ study of the reaction of S3N2Cl2 with AsF5 in SO2 solution.     

Hydrogen evolution from organic "hydrides"

Benzimidazolines (dihydrobenzimidazoles) are shown for the first time to eliminate hydrogen (H2) by catalyzed reaction with protic compounds.     

p(↑)+p(↑) → π+d at 515 and 578 MeV

The polarization asymmetries A_0y and A_y0, and the spin correlation parameter A_yy have been measured at SIN at 515 and 578 MeV using a transversally polarized proton beam and target. The results are compared with various theoretical models.