Hydrogen-atom Attack on Phenol and Toluene is \u3cem\u3eortho\u3c/em\u3e-directed

The reaction of H + phenol and H/D + toluene has been studied in a supersonic expansion after electric discharge. The (1 + 1′) resonance-enhanced multiphoton ionization (REMPI) spectra of the reaction products, at m/z = parent + 1, or parent + 2 amu, were measured by scanning the first (resonance) laser. The resulting spectra are highly structured. Ionization energies were measured by scanning the second (ionization) laser, while the first laser was tuned to a specific transition. Theoretical calculations, benchmarked to the well-studied H + benzene → cyclohexadienyl radical reaction, were performed. The spectrum arising from the reaction of H + phenol is attributed solely to the ortho-hydroxy-cyclohexadienyl radical, which was found in two conformers (syn and anti). Similarly, the reaction of H/D + toluene formed solely the ortho isomer. The preference for the ortho isomer at 100–200 K in the molecular beam is attributed to kinetic, not thermodynamic effects, caused by an entrance channel barrier that is ∼5 kJ mol−1 lower for ortho than for other isomers. Based on these results, we predict that the reaction of H + phenol and H + toluene should still favour the ortho isomer under elevated temperature conditions in the early stages of combustion (200–400 °C)

The optical spectrum of a large isolated polycyclic aromatic hydrocarbon: hexa-peri-hexabenzocoronene, C42H18

The first optical spectrum of an isolated polycyclic aromatic hydrocarbon large enough to survive the photophysical conditions of the interstellar medium is reported. Vibronic bands of the first electronic transition of the all benzenoid polycyclic aromatic hydrocarbon hexa-peri-hexabenzocoronene were observed in the 4080-4530 Angstrom range by resonant 2-color 2-photon ionization spectroscopy. The strongest feature at 4264 Angstrom is estimated to have an oscillator strength of f=1.4x10^-3, placing an upper limit on the interstellar abundance of this polycyclic aromatic hydrocarbon at 4x10^12 cm^-2, accounting for a maximum of ~0.02% of interstellar carbon. This study opens up the possibility to rigorously test neutral polycyclic aromatic hydrocarbons as carriers of the diffuse interstellar bands in the near future.Comment: 9 pages, 1 figure. Fixed a typo on the frequency of the 'b' ban

FULLY STATE-RESOLVED PHOTODISSOCIATION OF FORMALDEHYDE: H2_2CO\,→\rightarrow\,H\,+\,HCO. KK-CONSERVATION AND A RIGOROUS TEST OF STATISTICAL THEORIES

Author Institution: School of Chemistry, University of Sydney, NSW, 2006, AustraliaThe photodissociation dynamics of the reaction H$_2$CO + $h\nu$ $\rightarrow$ H + HCO have been investigated in the range 60-400\,cm$^{-1}$ above the reaction threshold. Supersonically-cooled formaldehyde was excited into 15 specific $J$, $K_a$, $K_c$ rotational states in two vibrational levels $2^14^16^1$ and $2^24^1$ in the $\tilde{\textrm{A}}$($^1A_2$) state. The laser induced fluorescence spectra of the nascent HCO fragment provided detailed product state distributions (PSDs), resolved by $N$, $K_a$, $K_c$ and $J$. When just the overall molecular rotation, $N$, is considered the PSDs are in remarkable agreement with calculations based on phase space theory (PST). However, when the projection of $N$ onto the molecular frame ($K_a$, $K_c$) is included the distributions show consistent deviations from PST. In particular, there is a tendency to preserve the initial parent rotational motion about the $a$ and $b$ axes. The effect is that states with higher initial $K_a$ in H$_2$CO produce higher final $K_a$ in the HCO fragment. There is also a tendency for the upper/lower members of the asymmetry doublets in H$_2$CO to map onto the same upper/lower set of product state asymmetry doublets. Finally, there are oscillations in some of the detailed PSDs that remain unexplained

Ondervoeding door een extreem gezondheidsdieet: EEN NIEUWE EETSTOORNIS?

A 71-year-old male was admitted to our hospital with heart failure, cachexia and biochemical disturbances due to a diet consisting of exclusively vegetables, oil and water. Our investigations showed that this diet was a consequence of an excessive preoccupation with health. The patient did not meet criteria for an eating disorder or other DSM-IV psychiatric disorder. We conclude that malnutrition due to health fad diets may be an underestimated medical problem. There is no specific psychopathological disorder that covers this behaviour, and there is no knowledge of its epidemiology. Popular literature is paying a great deal attention to orthorexia nervosa, an alleged eating disorder that describes a pathological obsession with healthy food. In medical literature this concept has been largely neglected, although eating disorder specialists frequently observe this behaviour in their practice. More clinical and scientific attention for this phenomenon is necessary to determine its epidemiology, validity and clinical picture

METAL CLUSTER FORMATION IN HELIUM NANODROPLETS

Author Institution: Dept. of Chemistry, University of North Carolina; Department of Chemistry, University of North CarolinaWe will discuss the formation of HCN-$Mg_{n}$ complexes in superfluid helium nanodroplets. The magnesium clusters are first formed in the helium droplets by sequential pick-up of gas phase atoms. The HCN is then added to the droplets and an F-center laser is used to excite the free C-H stretch. To aid in the search for the spectra of these metal complexes, we make use of the pendular method to collapse the ro-vibrational spectrum into a single peak. The dependence of the spectra on HCN pressure, Mg vapor pressure, droplet size and field strength provided assignments of HCN-$Mg_{n} (n = 1 - 6)$

STRUCTURE OF NAPHTHALENE DIMER INFERRED FROM SPECTRA OF NAPHTHALENE DIMER - ARGON VAN DER WAALS COMPLEXES

Author Institution: School of Chemistry, University of Sydney, NSW 2006, AustraliaWe have obtained resonant 2-colour 2-photon ionization spectra of Np$_n$Ar$_m$ (Np = naphthalene). While most spectra are broad and unresolved, those of Np$_2$Ar$_m$ arouse particular attention as they appear to consist of two independent and shifted electronic spectra. We consider our experimental data in the light of proposed structures for the naphthalene dimer and offer an alternative explanation for the observed broadening of the spectrum of Np$_2$ in terms of fragmentation of higher clusters