Rapid rotation about carbon-carbon bonds in alkyldiradicals. Mixtures of singlet and triplet methylene

Singlet methylene in the photolysis of mercury-ketene-butene systems

“…The major path (87 ± 2%) is diverted by 02 to the recently demonstrated oxidation pathways of triplet methylene shown in eq 6a and 6b.14 In the absence of 02, and after correction for the stereospecific 3CH2 + 802 -'(CHA) -* CO + H + OH (6a) \ C02 + H2 (6b) formation of DMC by eq 5, the ratio of ¿rans-DMC: cis-DMC is approximately 2.9, in agreement with the results for triplet reaction from direct ketene photolysis. 13 The ratio of frans-2-pentene: m-2-pentene, similarly corrected, is about 2.2, again in agreement with the direct-photolysis results.…”

“…cis-and írans-2-butene with ketene,9 the suggestion was made that 20-30% of the DMC formed in such reactions was actually the result of the stereospecific addition of singlet CH2 to 2-butene, as in eq 5. 13 We >CH2 + X*=\ (or \==/) -* \A^( or VV) (5) now report experimental results confirming the existence of two separate methylene reaction paths in the photolysis of mercury-ketene-butene systems. The lesser path (13 d= 2%) is stereospecific and not sensitive to 02 scavenger, consistent with the reactions of singlet methylene.…”

“…with methylene from the direct photoljrsis of ketene have led us to conclude that the addition of 8CH2 to 2-butene, as in eq 3 and 4, produces the same equilibrium ratio of 1,2-dimethylcyclopropanes (trans-DMC: cts-DMC =* 2.9) whether formed from cisor trans-2-butene. 13 The attainment of an equilibrium t)MC ratio requires that rotation about the single…”

Carbon-13 Fourier-transform nuclear magnetic resonance. I. Comparison of a simple spin-echo procedure with other methods

“…(9) I. Salmeen and . P. Klein, presented in part at the 11th Experimental Nmr Conference, Pittsburgh, Pa.,April 1970.…”

Oxidation of cerium(III) in sulfuric acid solutions induced by cobalt-60 .gamma.-radiation

“…with methylene from the direct photoljrsis of ketene have led us to conclude that the addition of 8CH2 to 2-butene, as in eq 3 and 4, produces the same equilibrium ratio of 1,2-dimethylcyclopropanes (trans-DMC: cts-DMC =* 2.9) whether formed from cisor trans-2-butene. 13 The attainment of an equilibrium t)MC ratio requires that rotation about the single 8CH2 + cis-or irans-CH8CH=CHCH3 -> CH3CHCHCH3 (3) <?H2 CH3CHQHCH3 -> QH2 CIS-or Zrans-CHgCHCHCHa (4) \/ CH2 bond in the diradical of eq 3 is much faster than the ring closure of eq '4 and further implies that gaseous systems in which such equilibrium is not found do not involve solely the reactions of triplet methylene. Since different ratios of the DMC products were measured in the mercury-photosensitized reactions of mixtures of…”