Electron-impact investigation of excited singlet states in 1,3-butadiene

Electron-impact energy-loss spectra of 1,3-butadiene have been obtained at impact energies from 35 eV to 90 eV, at a scattering angle of 0°, and at a     

The Reaction of P2I4 and N,N-dimethylformamide

P₂I₄ readily reacts with DME to give dimethyl-dodomethy leneammonium iodide, a compound of limited utility as a formylating agent.

Although diphosphorus tetraiodide (P₂I₄) has been known for many years, it has only recently sparked interest among organic chemists for use as a synthetic reagent. We initially became interested in P₂I₄ from a report that it cleanly reduced sulfoxides to sulfides.¹     

Methyl reorientation in solid 3-ethylchrysene and 3-isopropylchrysene

We have measured the proton spin-lattice relaxation rate as a function of temperature in polycrystalline 3-ethylchrysene at nuclear magnetic resonance Larmor frequencies of 53.0 and 22.5 MHz and in polycrystalline 3-isopropylchrysene at 53.0, 22.5 and 8.50 MHz. The syntheses of these new compounds are presented. The relatively large chrysene backbone creates an ideal and unique environment for the alkyl groups such that methyl group rotation is the only motion on the nuclear magnetic resonance Larmor frequency timescale over a large temperature range. The relaxation rate data are interpreted in terms of the simplest possible dynamical model; that of random hopping for the methyl group(s), all of which are equivalent in the solid state. The barriers of 11–12 kJ mol⁻¹ are typical for methyl groups in ‘isolated' ethyl and isopropyl groups.     

Investigation of routes to indeno[2,1-f] -2H-1,2,4-triazepinediones

The synthesis of a number of 3-(substituted thiosemiearbazido)-2-(a]koxycarbonyl)indones (1) from 2-alkoxycarbonyl-1, 3-indandiones and substituted thiosemicarbazides is described. Cyeliza-tion of compounds 1 in the presence of a variety of catalysts gave substituted Δ²-1,2,4-triazoline-5-thiones (³) and (⁴), instead of the expected substituted 3(4H)-thioxoindeno[2,1-f]-2H-1,2,4-triazepine-5(5aH),6-diones (2). The preparation of 4-(2-methyl-1,3-dioxo-2-indanylmethyl)semi-carbazide ( 9 ) is reported. Cyelization of 9 gave 5,5a-dihydro-5a-methylindeno[2,1-f]-2H-1,2,4-triazepine-3(4H),6-dione ( 10 ). Structure assignments of these compounds are discussed.     

5-Bromomethyl-4,5-dihydroisoxazoles

The preparation of substituted 4,5-dihydroisoxazoles can be accomplished via the treatment of β,γ-unsaturated oximes with liquid bromine. The reaction provides a convenient route to the highly functionalized title compounds.     

CIRCADIAN PHASE OF SPARROWS: CONTROL BY LIGHT AND DARK

Abstract— Sparrows ( Passer domesticus ) are day-active birds which exhibit circadian rhythms of perch-hopping activity. The phases of sparrow's circadian rhythms were studied following single 4 h light pulses, single 4 h dark pulses, doublet treatments of light and dark pulses, and a 10 h light pulse.
The sparrows exhibited a phase response curve to 4 h light pulses with maximum phase advances (3.8 h) at CT20 and maximum phase delays(–1.3 h) at CT16. The sparrows also displayed a phase response curve to dark pulses with maximum phase advances (2.2 h) at CT16 and maximum phase delays at CTO(–0.7 h).
The remaining pulses were imposed during the subjective dark-time. The 10 h pulse beginning 1 h after lights-out produced a 2.2 h phase shift. The doublet of 2 h pulses that were the "skeleton" of the 10 h pulse produced a 2.5 h phase shift. The early 2 h pulse, applied by itself resulted in a -0.4 h delay; the late 2 h pulse applied singly produced a 3.1 h advance. When an early 3 h dark pulse was imposed together with a late light pulse, the phase was advanced 3.6 h; singly the pulses produced 1.8 h and 2.7 h advances.     

Triplet states in 1,3-butadiene

The electron impact excitation spectrum 0f 1,3-butadiene has been studied at 20, 35 and 55 eV impact energies and scattering angles of 10° to 80°. Two low lying states are observed with maxima at 3.2 and 4.9 eV, and are identified as the ³B_u state and ³A_g state respectively     

Syn and Anti Isomer Preference in Oximes: An Undergraduate Organic Chemistry Experiment

An experiment is described that links a nucleophilic carbonyl addition reaction to a study of structure–activity relationships. Students prepare a series of oximes (from readily available ketones and aldehydes) and, with the use of NMR, define the ratio of syn and anti isomers formed in the reaction. From these data, a quantitative assessment of the steric hindrance of hydrogen, methyl, ethyl, isopropyl, and t–butyl can be obtained.