Gas-phase thermal decomposition of peroxy-N-butyryl nitrate

The gas-phase thermal decomposition rate of peroxy-n-butyryl nitrate (n-C₃H₇C(O)OONO₂, PnBN) has been measured at ambient temperature (296 K) and 1 atm of air relative to that of peroxyacetyl nitrate (CH₃C(O)OONO₂, PAN) using mixtures of PAN (14–19 ppb), PnBN (22–46 ppb), and nitric oxide (1.35–1.90 ppm). The PnBN/PAN decomposition rate ratio was 0.773 ± 0.030. This ratio, together with a literature value of 3.0 × 10^?4 s^?1 for the thermal decomposition rate of PAN at 296 K, yields a PnBN thermal decomposition rate of (2.32 ± 0.09) × 10^?4 s^?1. The results are briefly discussed by comparison with data for other peroxyacyl nitrates and with respect to the atmospheric persistence of PnBN. © 1994 John Wiley & Sons, Inc.     

Contents of Volume 6

Volume Contents

Contents of Volume 6     

Chemical modification of a viral cage for multivalent presentation

Here we present generalized methods for chemically modifying the surface of a viral protein cage; this exploits the chemistry of native and engineered surface exposed functional groups for multivalent presentation of ligands.     

Charged polypeptide vesicles with controllable diameter

We report the preparation and characterization of charged, amphiphilic block copolypeptides that form stable vesicles and micelles in aqueous solution. Specifically, we prepared and studied the aqueous self-assembly of a series of poly(L-lysine)-b-poly(L-leucine) block copolypeptides, KxLy, where x ranged from 20 to 80 and y ranged from 10 to 30 residues, as well as the poly(L-glutamatic acid)-b-poly(L-leucine) block copolypeptide, E60L20. Furthermore, the vesicular assemblies show dynamic properties, indicating a high degree of membrane fluidity. This characteristic provides stimuli-responsive properties to the vesicles and allows fine adjustment of vesicle size using liposome-based extrusion techniques. Vesicle extrusion also provides a straightforward means to trap solutes, making the vesicles promising biomimetic encapsulants.     

Surface phase separation in complex mixed adsorbing systems: an interface-bulk coupling effect

The interfacial thermodynamics and structure of ternary mixtures of the type A+B+solvent are investigated. According to the Gibbs phase rule, the coupling between the bulk phase and the interfacial region-which is related to the reversibility of the adsorption of the corresponding species-is a determinant as to whether phase separation can be observed at the interface. For an n-component adsorbing solution, at least one of the species has to adsorb irreversibly over the experimental time scales in order not to fix more intensive variables than those required to observe surface phase separation. We present results for a lattice model planar interface consisting of the ternary mixture A+B+solvent. The solvent molecules and the type A molecules have fixed chemical potentials at the interface since they are equilibrated with a bulk solution. In contrast, the type B molecules are irreversibly adsorbed at the interface and do not equilibrate with the bulk. Mean-field theory is compared with Monte Carlo simulation. Interestingly, the spinodal line in the interaction-composition plane shows a reentrant on the B-rich phase side. We discuss the implications of these results for surface phase separation of adsorbing mixtures of proteins and low-molecular-weight surfactants.     

X-ray structure of fac-[RuH(1,5-cod)(NH2NMe2)3][PF6]: Stabilization of coordinated substituted hydrazines by hydrogen bonding

The structure of [RuH(cod)(NH₂NMe₂)₃][PF₆] has been solved by X-ray diffraction methods and shows the cation to contain a facial arrangement of N,N-dimethylhydrazine ligands, coordinated via the NH₂ nitrogen atoms, and held together by hydrogen bonds.     

Solid products from thermal decomposition of polyethylene terephthalate: Investigation by CP/MAS 13C-NMR and fourier transform-IR spectroscopy

The solid reaction products from pyrolysis of polyethylene terephthalate in the presence and absence of red phosphorus were characterized by CP/MAS ¹³C-NMR, FR-IR, and MAS ³¹P-NMR spectroscopy. Over the temperature range of 300–400°C, polyethylene terephthalate was converted in a sealed vial to a highly crosslinked polymer of terephthalic acid. Pyrolysis in the presence of red phosphorus, which functions as a flame retardant by increasing the amount of char, yielded an intractible polyaromatic phosphate ester. After thermal cleavage of polyethylene terephthalate with formation of free carboxyl and vinyl ester groups, there are two competing reaction pathways. The smaller molecular weight fragments may enter the vapor phase where they undergo further degradation primarily to CO₂, CO, and acetaldehyde, as described by others. However, if volatilization of the oligomeric fragments is inhibited, an alternate reaction pathway gives rise to the formation of highly crosslinked char. Red phosphorus decreases the volatility of the oligomeric fragments by converting them to phosphates and thereby enhances char formation.     

An electronic aid for line selection for scanning inductively coupled plasma atomic emission spectrometers

This article is an electronic publication in Spectrochimica Acta Electronica (SAE), the electronic section of Spectrochimica Acta Part B (SAB). Accompanying this hard copy text is a disk containing the program, source flies, data files and a brief manual along with a few programming notes. The main article discusses the purpose of this work, and the Appendix provides brief instruction on the use of the program, manipulation of the data, and source code. An automatic file selection system for the control of a rapid scanning spectrometer performing atomic emission spectrometry has been developed using the PROLOG language. The system can be “taught” the elemental composition of a given sample type. It uses this information (when available) to generate a linear search strategy which minimizes the number of lines that need to be measured. The rules used by the system can be observed during system operation to allow a trace of the logic. Reading of the initial data base takes no more than 6 s and then decisions are made in less than 1 s per line.     

Preparation and photoelectron spectrum of the glycine molecular anion: assignment to a dipole-bound electron species with a high-dipole moment, non-zwitterionic form of the neutral core

We report the gas-phase preparation of negatively charged glycine as well as the Gly(H(2)O)(1,2) (-) complexes by entrainment of the neutral precursor into an ionized supersonic expansion tuned to optimize the (H(2)O)(n) (-)Ar(m) clusters. The photoelectron spectrum of Gly(-) displays the signature of a dipole-bound species, with sufficient vibrational fine structure to characterize the core neutral as a higher energy, non-zwitterionic isomer of the amino acid.