(endo)-5-(2-haloethyl)-2-norbornene. A new radical probe.

(endo)-5-(2-haloethyl)-2-norbornenes have been synthesized, and their corresponding radicals generated by reaction with sodium, magnesium, sodium naphthalenide and tri-n-butyltin hydride in the presence of AIBN to produce both straight chain and cyclized products. This probe cyclizes substantially faster than the often used 5-hexenyl halide probes.     

EPR evidence for a single electron transfer mechanism in reactions of aromatic ketones with lithium amides

Direct spectroscopic evidence (EPR) supporting a single electron transfer mechanism in the reaction of lithium amides with aromatic ketones is presented.     

Evidence for single electron transfer in the reaction of a lithium enolate with a primary alkyl iodide

Evidence for a radical process in the reaction of the lithium enolate of propiophenone with a primary alkyl iodide was obtained by the observation of cyclization of an appropriate radical probe, by the trapping of the radical intermediate and by the comparison of the relative rates of reactions of the probe alkyl iodide with the corresponding bromide and tosylate.     

The NMR spectra of some substituted dibenzothiophenes

In order to use the NMR spectra of dibenzothiophenes to determine the position of substitution, a series of compounds has been prepared, most of which are new while some represent an improved method of preparation of previously reported compounds. With the exception of one, the structures of the compounds prepared were not in doubt, however the splitting patterns and chemical shifts presented here will facilitate future structure determinations of dibenzothiophenes.     

Discontinuum between a thiolate and a thiol ligand

The effect of H-bond donation to the thiolate ligand of (eta(5)-C(5)H(5))Fe(CO)(2)SR (1) to give H-bond adducts (1 small middle dotHX) and eventually protonation to give [(eta(5)-C(5)H(5))Fe(CO)(2)(HSR)](+) (1H(+)()) has been investigated experimentally and computationally. The electronic structures of 1(R = Me), several derivatives of 1(R = Me) small middle dotHX, and 1(R = Me)H(+)() have been investigated using DFT (density functional theory) computational methods. As previously suggested, these calculations indicate the HOMO of 1 is Fedpi-Sppi antibonding and largely sulfur in character. The calculations indicate the electronic structure of 1 is not altered markedly by H-bond donation to the S center, but protonation results in a reorganization of the electronic structure of 1H(+)() and a HOMO that is largely metal in character. The reduction of Fe-S distances upon protonation of 1(R = Ph) to give 1(R = Ph)H(+)() small middle dotBF(4)()(-)() (2.282(2) and 2.258(2) A, respectively), as determined by single-crystal X-ray crystallography, also indicates diminished Fedpi-Sppi antibonding. Using the carbonyl stretching frequencies as a gauge of the donor ability of the thiolate ligand, we conclude that H-bonding has a continuous effect on the donor properties of the thiolate ligand of 1 (i.e., is a function of the pK(a) of the H-bond donor). A discontinuous effect results when the pK(b) of 1 is reached and the complex is protonated. For our study of 1, the maximal effect of H-bonding is about 30% of protonation. Because the position of acid-base equilibrium depends on the relative basicities of the thiolate ligand and the conjugate base of the H-bond donor (and the relative heats of solvation of the acids and their conjugate bases), a true continuum of effects can be anticipated only for systems that are pK-matched in their given environments. Thus, when the conjugate base of the H-bond donor is a stronger base than the thiolate ligand (as in the present case), H-bond donation has a relatively small effect, but protonation triggers a large, discontinuous effect on the electronic structure of 1.     

The link between nanoscale feature development in a negative resist and the Hansen solubility sphere

By systematically studying development of a high resolution, negative electron beam resist, hexa‐methyl acetoxy calix(6)arene, we have elicited a more general understanding of the underlying development mechanisms for negative resists. Using the three dimensional Hansen solubility parameters for more than 40 solvents, we have constructed a Hansen solubility sphere (HSS). From this sphere, we have estimated the Flory Huggins interaction parameter for solvents with hexa‐methyl acetoxy calix(6)arene and found a correlation between resist development contrast, nanoscale patterned feature quality, and the polymer‐solvent solubility. Conducting Atomic Force Microscopy (AFM) in a liquid cell, we have measured swelling for hexa‐methyl acetoxy calix(6)arene in four solvents. The swelling measurements indicate that the HSS gives an indication of the Flory‐Huggins interaction parameter. These measurements provide new insights into the development behavior of nanoscale features – necessary for obtaining the ultimate lithographic resolution. In addition, it demonstrates a methodology for choosing appropriate polymer‐solvent combinations for nanoscience applications. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 2091–2105, 2009     

Effects of Testosterone Replacement on a Male Professional Singer

Testosterone has been known to play an important role in the development of the postpubertal male voice for many centuries. In fact, the prevention of pubertal development of the voice by castrating young male singers was a well-known practice, especially in Italy beginning in the sixteenth century. The “castrati” were well known for their clear, high-pitched voices. Because of the resulting small larynx and vocal folds, castrati apparently produced a distinctive resonance as well as the high pitch, which cannot be matched even by the counter tenors of today. Busy voice labs occasionally see males with sex hormone deficiencies secondary to chromosomal or gonadal problems. This is a presentation of an unusual patient who was a trained tenor singer and was found to have hypogonadism on a premarital health examination. Administration of replacement testosterone resulted in significant vocal register and voice quality changes.     

Measurement of isotope shifts,fine and hyperfine structure splittings of the lithium D lines

The lithium D lines were studied using a diode laser that was frequency modulated by an electro-optic modulator, to excite an atomic beam. The transmission of part of the laser beam through an etalon was monitored to correct for the nonlinearity of the laser scan. The results for the ^6,7Li 2 S _1/2 and 2 P _1/2 hyperfine splittings agree very well with the best existing data while those for the D1 isotope shift and ^6,7Li fine structure splittings disagree significantly from data obtained by a previous laser atomic beam experiment. Our result for the D1 isotope shift is very close to the latest value computed using Hylleraas variational theory. Received 8 April 2002 / Received in final form 26 June 2002 Published online 21 January 2003 RID="a" ID="a"e-mail: wvw@yorku.ca     

Evidence supporting a single electron transfer pathway in the reduction of aromatic ketones by metal alkoxides. Lithium isopropoxide,an excellent reducing agent for aromatic ketones.

Reactions of various metal alkoxides with aromatic ketones have been shown to produce radical intermediate. Lithium isopropoxide has been found to be an excellent reducing agent for aromatic ketones and reduces benzophenone at a faster rate than does aluminum isopropoxide.     

Evidence for single electron transfer in the reduction of alcoholswith lithium aluminum hydride

EPR evidence supporting a single electron transfer mechanism in the reduction of secondary and tertiary alcohols to hydrocarbons with LiAlH₄ is presented.