Partially fluorinated heterocycles. Part 25[1]. The formation of fused-ring 3 -azepine derivatives: 6,7,8,9-Tetrafluoro-2,4-diphenyl-3 -1-benzazepine and 6,7,8,9,10,11-hexafluoro-2,4-diphenyl-3 -naphth[2,1-b] azepine

Pentafluoroaniline(1) and 1,3,4,5,6,7,8-heptafluoro-2-naphthylamine(2) react with acetophenone in tetralin at reflux temperature in the presence of anhydrous zinc chloride to give the 3 -azepine derivatives 6,7,8,9-tetrafluoro-2,4,-diphenyl-3 -1-benzazepine (5) and 6,7,8,9,10,11-hexafluoro-2,4,-diphenyl-3 -napth[2,1-b]azepine (6) respectively, in addition to the Schiff bases (3) and (4), found previously. The self-condensation product of acetophenone, β-benzoyl-α-methylstyrene (“dypnone”), is an intermediate in the ring-forming reactions. The heterocycles (5) and (6) exhibit fluxional behaviour which at 297K is fast for (5) but slow for (6) on the NMR time-scale.     

Synthesis of Orthogonally Protected S,S-2,6-Diaminopimelic Acid via Olefin Cross-Metathesis

A short synthesis of orthogonally protected S,S-diaminopimelic acid, DAP, via a selective cross-metathesis between S-allyl glycine and S-vinyl glycine followed by hydrogenation is reported. By analogy, the S,S-diaminosuberic acid, DAS, is produced by self-metathesis of S-allyl glycine, and the self-metathesis of S-vinyl glycine is described.     

Volume-based thermodynamics: estimations for 2:2 salts

The lattice energy of an ionic crystal, U(POT), can be expressed as a linear function of the inverse cube root of its formula unit volume (i.e., Vm(-1/3)); thus, U(POT) approximately 2I(alpha/Vm(1/3) + beta), where alpha and beta are fitted constants and I is the readily calculated ionic strength factor of the lattice. The standard entropy, S, is a linear function of Vm itself: S approximately kVm + c, with fitted constants k and c. The constants alpha and beta have previously been evaluated for salts with charge ratios of 1:1, 1:2, and 2:1 and for the general case q:p, while values of k and c applicable to ionic solids generally have earlier been reported. In this paper, we obtain alpha and beta, k and c, specifically for 2:2 salts (by studying the ionic oxides, sulfates, and carbonates), finding that U(POT)[MX 2:2]/(kJ mol(-1)) approximately 8(119/Vm(1/3) + 60) and S degree [MX 2:2]/(J K(-1) mol(-1)) approximately 1382V(m) + 16.     

2,3,4,5,7-pentafluorotricyclo(3.3.1.02,7) non-3-en-6-one,an internal Diels-Alder adduct from the Claisen rearrangement intermediate from pentafluorophenyl prop-2-enyl ether

The title compound (3), the first carbocyclic Diels-Alder adduct to be isolated from the Claisen rearrangement intermediate from the thermolysis of an aryl $\text{prop-2-enyl}$ ether, has been characterised from its spectroscopic data and by its conversion to 1,2,3,4,7-pentafluorotricyclo [3.3.1.0^2,7]non-3- en-8,8 diol hemihydrate (5).     

Tunable laser photodissociation: quantum yield of I★(2P12) from Ch2I2

Tunable laser I^★(²P_{$\text{1}\text{2}$}) quantum-yield measurements are presented for CH₂I₂ in the wavelength range 248–340 nm. The results suggest that a curve-crossing mechanism is operative in the dissociation.     

Shock tube study of OH reactions with linear hydrocarbons near 1100 K

Reactions of the hydroxyl radical with several linear hydrocarbon species occurring in combustion chemistry have been considered at temperatures near 1100 K and 1 atmosphere in shock tube experiments. The OH density was monitored using 310 nm UV absorption of the A²Σ⁺ (SINGLEBOND) X ²Π transition. Rate coefficients for the reaction of OH with ethane (8.37 × 10⁻¹² cm³ molecule⁻¹ s^{− 1}; 970 K), hexane (2.18 × 10⁻¹¹; 962 K), heptane (3.34 × 10⁻¹¹, 1186 K), octane (4.42 × 10⁻¹¹; 1078 K), nonane (4.55 × 10⁻¹¹; 1097 K), and decane (5.64 × 10⁻¹¹; 1109 K) have been determined. These values are compared with previous experimental results and transition state theory calculations. © 1996 John Wiley & Sons, Inc.     

Aqueous RAFT Synthesis of Low Molecular Weight Anionic Polymers for Determination of Structure/Binding Interactions with Gliadin

Gliadin, a component of gluten and a known epitope, is implicated in celiac disease (CeD) and results in an inflammatory response in CeD patients when consumed. Acrylamide‐based polyelectrolytes are employed as models to determine the effect of molecular weight and pendent group on non‐covalent interaction modes with gliadin in vitro. Poly(sodium 2‐acrylamido‐2‐methylpropane sulfonate) and poly(sodium 3‐methylpropyl‐3‐butanoate) are synthesized via aqueous reversible addition fragmentation chain transfer (aRAFT) polymerization and characterized by gel permeation chromatography‐multiangle laser light scattering. The polymer/gliadin blends are examined via circular dichroism, zeta potential measurements, 8‐anilinonaphthalene‐1‐sulfonic acid fluorescence spectroscopy, and dynamic light scattering. Acrylamide polymers containing strong anionic pendent groups have a profound effect on gliadin secondary structure and solution behavior below the isoelectric point, while polymers containing hydrophobic character only have a minor impact. The polymers have little effect on gliadin secondary structure and solution behavior at the isoelectric point.     

Crystal-amorphous polymer interface studied by neutron and x-ray scattering on labeled binary ultralong alkanes

The recently discovered stable semicrystalline phase in binary ultralong alkanes is studied by small-angle neutron and x-ray scattering. Either the shorter or the longer alkane has (CD2)11CD3 ends. It is confirmed that chains are tilted in the crystal layer and found that ca. seven end carbons of the shorter alkane are amorphous. It is also established that the longer chains protrude from the crystal at both ends and that their end groups are preferentially located in the middle of the amorphous layer, suggesting gradual dissipation of orientational order of the chains exiting the crystal.     

Symmetric spectra

The stable homotopy category, much studied by algebraic topologists, is a closed symmetric monoidal category. For many years, however, there has been no well-behaved closed symmetric monoidal category of spectra whose homotopy category is the stable homotopy category. In this paper, we present such a category of spectra; the category of symmetric spectra. Our method can be used more generally to invert a monoidal functor, up to homotopy, in a way that preserves monoidal structure. Symmetric spectra were discovered at about the same time as the category of -modules of Elmendorf, Kriz, Mandell, and May, a completely different symmetric monoidal category of spectra.