Reviews of books

Abstract

This well known collection of molecular absorption spectra, which now includes 2461 spectra housed in 14 volumes, becomes-as it grows-ever more valuable. Volume XIV includes many heterocyclic compounds displaying aromaticity.

Very low‐pressure pyrolysis (VLPP) of but‐1‐yne the heat of formation and stabilization energy of the propargyl radical

“…The value of 8 kcal/mol for SE"(HCCCH2) from the recent electronimpact study by Sen Sharma and Franklin [8] is in good agreement with the conclusions reached here, but the value of 4.1 kcal/mol obtained by Walsh [5] from the iodine-catalyzed isomerization of methylacetylene is surprisingly far because kinetic studies of the gas-phase reactions of iodine with organic species have generally yielded reliable C-H bond dissociation energies [27]. There may be some as yet unexplained errors in Walsh's work.…”

“…Thus the kinetic parameters for C-C fission adjacent to the acetylenic group in alkynes will lead to heats of formation of propargylic radicals which are particularly interesting because they are resonance stabilized [1,4-61. From his study of 4-methylpent-1-yne, Tsang obtained log kl(sec-') = 15.56 -69.4/8, from which he derived AHi,300(HCCCH2) = 80.7 kcal/mol, which is lower than the value of 86 kcal/mol obtained by Walsh [5] from a study of the iodine-catalyzed isomerization of methylacetylene. Electron impact studies by Collin and Lossing [7] and Sen Sharma and Franklin [8] have yielded values of 75 and 82 kcal/mol, respectively.…”

Thermal stability of intermediate sized acetylenic compounds and the heats of formation of propargyl radicals

“…The specific results of interest are evidence for both molecular and bond-breaking channels for decomposition with rate ex-International Journal of Chemical Kinetics, Vol. X, 687-711 (1978) When this is combined with [a] h~(2-methylpentanen -propyl + isopropyl) = 1ol6.l exp(-39,400/T) sec-1 one obtains for the propargyl resonance energy D(nC3H7-H) -D(C3H3-H) = 37.9 kJ (1100°K) and 38.9 kJ (300°K) Subsequently Walsh [3] carried out a study on the iodine catalyzed isomerization of methylacetylene and concluded that the propargyl resonance energy is 16.8 kJ using a value of D(nC3H7-H) = 410 kJ. This is an enormous discrepancy and is far larger than can be expected on the basis of the assumptions inherent in both methods.…”

Very low‐pressure pyrolysis (VLPP) of 3,3‐dimethylbut‐1‐yne (tert‐butyl acetylene). The heat of formation and stabilization energy of the dimethylpropargyl radical

“…The combined results indicate that propargylic radicals are more stable than acyanoalkyl radicals [l-31 but less stable than allylic radicals [20,22]. The value obtained by Walsh [6] for the propargyl stabilization energy may be too low.…”

“…An early electron-impact study by Collin and Lossing [4] yielded aHj(CH2CCH) = 75 kcal/mol, while a more recent investigation by Sen Sharma and Franklin [5] yielded a value of 82 kcalfmol. Walsh [6] obtained a value of 86 from a study of the iodinecatalyzed isomerization of methylacetylene, and Tsang [7] obtained a value of 80.7 from a study of the shock-tube pyrolysis of 4-methylpent-l-yne. These data lead to values for the propargyl stabilization energy of 15.3,8,4.1, and 9.6 kcal /mol, respectively.…”