Alkylation of 3-Ethoxy-2-Lithioacrylonitrile: Synthesis of 5-Alkylcytosines

The utility of commercially available, inexpensive 3-ethoxyacrylonitrile (1) as a precursor for the synthesis of 5-alkylcytosines was investigated. Metalation of 1 affords a 2-lithio derivative of sufficient stability to allow alkylation with allylic or benzylic bromides and primary iodides which are unbranched at the β-position. The alkylated derivatives are converted to 5-alkylcytosines in modest yield by exposure to sodium ethoxide and urea in ethanol.     

Atomgewichte

Ohne Zusammenfassung     

Simplicity of lie module triple systems

We analyze how certain constructions of Lie module triple systems affect the structure theory, particularly simplicity. We are thus able to show that there is no upper bound on the number of summands in a direct sum decomposition of a simple Lie module triple system as a module for its inner derivation algebra.     

Ground-state and excited-state structures of tungsten-benzylidyne complexes

The molecular structure of the tungsten-benzylidyne complex trans-W(≡CPh)(dppe)(2)Cl (1; dppe = 1,2-bis(diphenylphosphino)ethane) in the singlet (d(xy))(2) ground state and luminescent triplet (d(xy))(1)(π*(WCPh))(1) excited state (1*) has been studied using X-ray transient absorption spectroscopy, X-ray crystallography, and density functional theory (DFT) calculations. Molecular-orbital considerations suggest that the W-C and W-P bond lengths should increase in the excited state because of the reduction of the formal W-C bond order and decrease in W→P π-backbonding, respectively, between 1 and 1*. This latter conclusion is supported by comparisons among the W-P bond lengths obtained from the X-ray crystal structures of 1, (d(xy))(1)-configured 1(+), and (d(xy))(2) [W(CPh)(dppe)(2)(NCMe)](+) (2(+)). X-ray transient absorption spectroscopic measurements of the excited-state structure of 1* reveal that the W-C bond length is the same (within experimental error) as that determined by X-ray crystallography for the ground state 1, while the average W-P/W-Cl distance increases by 0.04 ? in the excited state. The small excited-state elongation of the W-C bond relative to the M-E distortions found for M(≡E)L(n) (E = O, N) compounds with analogous (d(xy))(1)(π*(ME))(1) excited states is due to the π conjugation within the WCPh unit, which lessens the local W-C π-antibonding character of the π*(WCPh) lowest unoccupied molecular orbital (LUMO). These conclusions are supported by DFT calculations on 1 and 1*. The similar core bond distances of 1, 1(+), and 1* indicates that the inner-sphere reorganization energy associated with ground- and excited-state electron-transfer reactions is small.     

Effects of structure variation on solution properties of hydrotropes: phenyl versus cyclohexyl chain tips

The physicochemical behavior of the phenyl-n-alkanoate (PhenCx) and cyclohexyl-n-alkanoate (CyclohexCx) series has been investigated, supporting previous work on the understanding of hydrotropes (Hopkins Hatzopoulos, M.; Eastoe, J.; Dowding, P.J.; Rogers, S. E.; Heenan, R.; Dyer, R. Langmuir2011, 27, 12346-12353). Electrical conductivity, surface tension, (1)H NMR, and small-angle neutron scattering (SANS) were used to study adsorption and aggregation in terms of critical aggregation concentration (cac). The PhenCx series exhibited very similar d log(cac)/dn to n-alkylbenzoates (CnBenz), exhibiting two branches of behavior, with a common inflection point at four linear carbons, whereas the CyclohexCx series showed no break point. Electrical conductivity and (1)H NMR concentration scans indicate a difference in physicochemical behavior between higher and lower homologues in both the PhenCx and CyclohexCx series. Surface tension measurements with compounds belonging to either group gave typical Gibbs adsorption profiles, having d log(cac)/dn curves consistent with limiting headgroup areas in the region of (35-55 ?(2)) indicating monolayer formation. SANS profiles showed no evidence for aggregates below the electrical conductivity determined cac values, inferring an "on-off" mode of aggregation. Analyses of SANS profiles was consistent with charged ellipsoidal aggregates, persisting from lower through to higher homologues in both the PhenCx and CyclohexCx series.     

An in-depth in situ IR study of the thermal decomposition of yttrium trifluoroacetate hydrate

The pyrolysis of Y(CF₃COO)₃·nH₂O at temperatures up to 1,000 °C, under flowing pure Ar, O₂ and O₂ saturated with water vapour, was extensively analysed. The formation of HF is observed directly and the existence of a :CF₂ diradical is inferred during a trifluoroacetic acid salt decomposition. High resolution thermogravimetry, differential scanning calorimetry, X-ray diffractometry and scanning electron microscopy indicated that the exothermic one-stage decomposition of the anhydrate salt occurs at 267 °C, forming YF₃. Fourier transform infrared spectroscopy identified (CF₃CO)₂O, CF₃COF, COF₂, CO₂ and CO as the principal volatile species; and revealed the influence of water on the reactions liberating gaseous CF₃COOH, CHF₃, HF, and SiF₄ (from reactions with glass or quartz components). NO₂ and N₂O evolution suggested that traces of CH₃NO₂ were present in the starting material. Thermogravimetry and X-ray diffractometry indicated that the slow hydrolysis of the fluoride occurs between 630 and 655 °C, forming a mixture of Y₂O₃, YOF, Y₇O₆F₉, and YF₃. The decomposition and hydrolysis temperatures are significantly lower than previously reported, which has implications for sol–gel processing.     

Measurement of pressure and density inside a single sonoluminescing bubble

The average pressure inside a sonoluminescing bubble in sulfuric acid has been determined by two independent techniques: (1) plasma diagnostics applied to Ar atom emission lines, and (2) light scattering measurements of bubble radius vs time. For dimly luminescing bubbles, both methods yield intracavity pressures approximately 1500 bar. Upon stronger acoustic driving of the bubble, the sonoluminescence intensity increases 10,000-fold, spectral lines are no longer resolved, and radius vs time measurements yield internal pressures > 3700 bar. Implications for a hot inner core are discussed.