The First Turbulence and First Fossil Turbulence

A model is proposed connecting turbulence, fossil turbulence and the big-bang origin of the universe. While details are incomplete, the model is consistent with our knowledge of these processes and is supported by observations. Turbulence arises in a hot big-bang quantum gravitational dynamics scenario at Planck scales. Chaotic, eddy-like motions produce an exothermic Planck particle cascade from 10^?35 m at 10³² K to 10⁸ larger, 10⁴ cooler, quark-gluon scales. A Planck-Kerr instability gives high Reynolds number (Re ～ 10⁶) turbulent combustion, space-time-energy-entropy and turbulent mixing. Batchelor-Obukhov-Corrsin turbulent-temperature fluctuations are preserved as the first fossil turbulence by inflation stretching the patterns beyond the horizon ct of causal connection faster than light speed c in time t～ 10^?33 sec. Fossil big-bang temperature turbulence reenters the horizon and imprints nucleosynthesis of H-He densities that seed fragmentation by gravity at 10¹² s in the low Reynolds number plasma before its transition to gas at t～ 10¹³ s and T～ 3000 K. Multiscaling coefficients of the cosmic microwave background (CMB) temperature anisotropies closely match those for high Reynolds number turbulence, Bershadskii, A. and Sreenivasan, K.R., Phys. Lett. A 299 (2002) 149-152; Bershadskii, A. and Sreenivasan, K.R., Phys. Lett. A 319 (2003) 21-23. CMB spectra support the interpretation that big-bang turbulence fossils triggered fragmentation of the viscous plasma at supercluster to galaxy mass scales from 10⁴⁶ to 10⁴² kg, Gibson, C.H., Appl. Mech. Rev. 49 (5) (1996) 299-315; Gibson, C.H., J. Fluids Eng. 122 (2000) 830-835; Gibson, C.H., Combust. Sci. Technol. (2004, to be published).     

Microporous Molecular Materials from Dipeptides Containing Non‐proteinogenic Residues

Dipeptides with two hydrophobic side chains have proved to be an exceptional source of microporous organic materials, but since previous structures were limited to the incorporation of only proteinogenic residues, their full potential as adsorbents has remained unexplored. Single‐crystal XRD data for ten new compounds with non‐proteinogenic L ‐2‐aminobutanoic acid and/or L ‐2‐amino‐pentanoic acid are presented. The gas‐phase accessibility of their crystal pores, with cross‐sections of 2.3 to 5.1 Å, was monitored by CO₂ and CH₄ adsorption isotherms. Included CO₂ was also detected spectroscopically by 2D MAS NMR. An extensive conformational analysis reveals that the use of linear rather than branched side chains (such as L ‐valine and L ‐isoleucine) affords peptides with a greater degree of conformational freedom and yields more‐flexible channel surfaces that may easily adapt to a series of potential guest molecules.     

Mild route to generate gaseous metal anions

Gaseous metal anions such as Na(-), K(-), Cs(-), and Ag(-) can be generated at ambient temperatures by the collision-induced dissociation of the anions of several dicarboxylic acid salts, including oxalate, maleate, fumarate, succinate, and glutamate salts. The formation of gaseous metal anions in this way is unprecedented because the metal is initially present in its cationic form. The mild process described here could facilitate novel applications of metal anions as selective reagents for gas-phase ion-molecule and ion-ion reactions. Ab initio calculations were used to describe the dissociation process for anions of the oxalate salts. The formation of alkalides occurs via production of a metal-carbon dioxide anion intermediate with a bidentate three-center two-electron bond to the metal. The metal atom acquires a partial negative charge in the intermediate structure.     

Structural basis for the exceptional stability of bisaminoacylated nucleotides and transfer RNAs

At least one bisaminoacyl-tRNA is synthesized in nature (by Thermus thermophilus phenylalanyl-tRNA synthetase), and many disubstituted tRNAs have been prepared in vitro. Such misacylated tRNAs are able to participate in protein synthesis, even though they lack the free 2'-OH group of the 3'-terminal adenosine moiety. Their ready participation in protein synthesis implies significant chemical reactivity. The basis for this reactivity has been documented previously. Surprisingly, the aminoacyl moieties of these tRNAs also exhibit exceptional chemical stability. In the present report, bisaminoacylated nucleotides are investigated computationally and experimentally to define the basis for the stability of such species. Molecular modeling of bisalanyl-AMP in the absence of solvent and in the presence of a limited number of water molecules revealed two common features among the low-energy structures. The first was the presence of H-bonding interactions between the two aminoacyl moieties. The second was the presence of a H-bonding interaction between the 2'-O-alanyl moiety and the N-3 atom of the adenine nucleobase, typically mediated through a water molecule. The prediction of an interaction between an aminoacyl moiety and the adenine nucleobase was confirmed experimentally by comparing the behavior of bisalanyl-AMP and bisalanyl-UMP in the presence of model nucleophiles. This study suggests a possible role for the adenosine moiety at the 3'-end of aminoanyl-tRNAs in controlling the stability and reactivity of the aminoacyl moiety and has important implications for the reactivity and stability of normal aminoacyl-tRNAs.     

The C-H bond dissociation energy of furan: photoelectron spectroscopy of the furanide anion

Using photoelectron spectroscopy, we interrogate the cyclic furanide anion (C(4)H(3)O(-)) to determine the electron affinity and vibrational structure of the neutral furanyl radical and the term energy of its first excited electronic state. We present the 364-nm photoelectron spectrum of the furanide anion and measure the electron affinity of the X?(2)A(') ground state of the α-furanyl radical to be 1.853(4) eV. A Franck-Condon analysis of the well-resolved spectrum allows determination of the harmonic frequencies of three of the most active vibrational modes upon X?(2)A(') ← X?(1)A(') photodetachment: 855(25), 1064(25), and 1307(40) cm(-1). These modes are ring deformation vibrations, consistent with the intuitive picture of furanide anion photodetachment, where the excess electron is strongly localized on the α-carbon atom. In addition, the A?(2)A(') excited state of the α-furanyl radical is observed 0.68(7) eV higher in energy than the X?(2)A(') ground state. Through a thermochemical cycle involving the known gas-phase acidity of furan, the electron affinity of the furanyl radical yields the first experimental determination of the C-H(α) bond dissociation energy of furan (DH(298)(C(4)H(3)O-H(α))): 119.8(2) kcal mol(-1).     

Treasures from the Free Radical Renaissance Period--miscellaneous hexenyl radical kinetic data

Rate constant data and Arrhenius parameters have been determined for a series of substituted hexenyl radicals of differing electronic and steric demand. Electron-withdrawing groups (CF(3), CO(2)Et) directly attached to the radical centre slightly accelerate 5-exo ring-closure (k(cis) + k(trans) ～ 2.1 × 10(5) s(-1) at 25°) relative to donating groups (OMe; 1.6 × 10(5) s(-1) at 25°). Sterically demanding groups (tert-Bu), as expected, slow the cyclization process (1 × 10(5) s(-1)). These observations are consistent with subtle changes in activation energy for 5-exo ring-closure. Interestingly, the nature of the solvent would appear to have a significant influence on this chemistry with the cis/trans stereoselectivity sometimes improved as the solvent polarity is increased. Except for the system containing the CF(3) (electron-withdrawing) group which displays an increase in the cyclization/capture rate constant (k(c)/k(H)), a general decrease in the k(c)/k(H) ratio as solvent polarity is increased is noted; these changes have been speculated to arise mainly from changes in k(H) in the various solvents employed.     

2-[1-(2,6-Dibenzhydryl-4-methylphenylimino)ethyl]-6-[1-(arylimino)ethyl]pyridylcobalt(II) dichlorides: synthesis, characterization and ethylene polymerization behavior

A series of unsymmetrical 2,6-bis(imino)pyridylcobalt(II) complexes, {2-[2,6-(CH(C(6)H(5))(2))(2)-4-Me-C(6)H(2)N==C(CH(3))]-6-(2,6-R(1)(2)-4-R(2)-C(6)H(2)N==CCH(3))-C(5)H(3)NCoCl(2)} where R(1) = Me, Et or (i)Pr, R(2) = H or Me, together with the new symmetrical complex 2,6-[2,6-(CH(C(6)H(5))(2))(2)-4-Me-C(6)H(2)N==C(CH(3))](2)-C(5)H(3)NCoCl(2), were synthesized. All of the compounds were fully characterized by (1)H NMR and IR spectroscopy, as well as by elemental analysis. The molecular structures of Co1 (R(1) = Me, R(2) = H) and Co5 (R(1) = Et, R(2) = Me) were further confirmed by single crystal X-ray diffraction, which indicated that the cobalt centres were penta-coordinate with a pseudo square-pyramidal geometry. Upon treatment with MAO or MMAO, these cobalt pre-catalysts exhibited higher activities than any previously reported cobalt pre-catalysts, with values as high as 4.64 × 10(6) g PE mol(-1)(Co) h(-1) for ethylene polymerization at atmospheric pressure. The polyethylenes obtained were of high molecular weight and narrow molecular weight distribution.     

Stereoselective rhodium-catalyzed amination of alkenes

The first stereoselective rhodium-catalyzed intermolecular aziridination and C-H amination of alkenes to produce chiral carbamate-protected aziridines and allylic amines is described. Good yields and diastereoselectivities were achieved using a readily available chiral N-tosyloxycarbamate and stoichiometric amount of the alkene substrate. Furthermore the protecting group is easy to cleave under mild reaction conditions.     

Diversity-oriented approach to pyrrole-imidazole alkaloid frameworks

An exploration of imidazolylpropargyl amides as linchpin synthons for the construction of a diverse array of heterocyclic frameworks, many of which are related to those found in the oroidin derived alkaloids, is described. One such intermediate has been used in a formal total synthesis of cyclooroidin.     

Synthesis of 2-imidazolones and 2-iminoimidazoles

Convenient methods for the direct conversion of imidazolium salts to the corresponding 2-imidazolone or 2-imino imidazole derivatives have been developed. Treatment of the salt with commercial bleach leads to effective oxidation at C2 and the formation of the corresponding imidazolone. Alternatively, treatment of the salt with an N-chloro amide affords the corresponding protected 2-amino derivative in good yield.