The Chemistry of Singlet and Triplet Methylene

Abstract

Results are reported for the photolysis of small, fixed amounts of diazomethane and cisbutene-2 in the presence of increasing pressures of the inert gases He, Ar, Xe, Nz, and CFa.The variation in the percentage yield of the trans-din~ethylcyclopropane a s a function of the inert gas pressure indicates that two basic mechanisms, with opposite dependencies on the inert gas pressure, are responsible for its formation. An initial decrease in the percentage yield of this trans isomer with increasing pressure indicates that a source is an isomerization of energized molecules. These excited molecules result from the addition of methylene in a singlet state t o cis-butene-2. A subsequent rise in t h e yield of t h e trans isomer with further increases in the pressure indicates that another mechanism, one whose rate is increased by a n increase in pressure, must be present. This is attributed to a mechanism involving triplet methylene. ?'he pressure regions for the observation of the singlet or triplet behavior of methylene are thus ltnown and the inodes of formation of the other C6 products may be determined.

Wavelength dependency of the relative proportions of singlet/triplet methylenes from the photolysis of diazomethane

“…Found: C, 67.44; H, 7.39. Tl~ymoquinol Diacetate (6) This conlpound was obtained by reductive acetylation of thymoquinone (2) in an acetic anhydride -zinc dusthydrochloric acid mixture by a modification of a standard procedure (3). The product was obtained as a white solid (79% yield) n1.p.…”

Intramolecular comparison of the insertion into the carbon-hydrogen bonds of alkanes by singlet methylene radicals

“…^Ri^r/' V >/RiWk11/2 -yPjWp/^/ %77 , /2Í ( Ri*Rt Pi ) (8) where reactant Ri has been selected as a reference species and T is the temperature of the gas surrounding the particle. The sum over 4) the products, is understood to include only those species which leave the particle surface.…”

Addition to Alkenes

“…Obviously, the intermediate(s) involved in the pyrolysis of [13] are not on the reaction coordinate in the addition of singlet methylene to eis-and r?my-2-butene. It is important, therefore, to see whether two substituents on carbon atoms 1 and 2 retain their relative configuration during ring closure.…”