The intrinsic advantage proffered by coupled three-proton spin systems in the quantitative study of conformational equilibria and equilibrations, as elaborated and exemplified in the preceding publication, is exploited for the determination of precise thermodynamic and dynamic parameters for octadeuteriocyclohexanes containing a cyano, chloro, bromo or deuteriomethoxy substituent and hydrogen atoms on the substituted and on one contiguous carbon. Dynamic quantities for the ring reversal of cyclohexane-1,1,2,2,3,3,4,4-4, obtained by bandshape analysis of the deuterium-decoupled proton NMR spectra broadened by mutual four-spin exchange, are also reported. The measured standard entropy differences between the axial and equatorial conformational isomers of the monosubstituted cyclohexanes show that, in addition to the rotational entropy, there must be a significant contribution from the vibrational partition functions. The experimental activation entropies for the cyclohexane chair-to-twist-boat conversion are at variance with conclusions drawn from naive symmetry considerations, but agree with the more sophisticated treatment of Pickett and Strauss; the data establish that there is virtually free pseudorotation in the transition states of the ring reversal for cyclohexane itself as well as for the monosubstituted derivatives studied in this investigation.
The diene adduct of 2-chloroacrylonitrile and abietic acid (1) can be converted to tetracyclic ketone 2. Oxidation of 1 and 2 with ozone, KMnO 4 , OsO 4 , and tert-butylchromate are described. Three products have been further oxidized by Baeyer-Villiger reactions.
Addition of acetylene dicarboxylic acid dimethylester to abietic acid is an en-reaction. The structure of the resulting product was determined. Compounds formally derived from addition of acetylene to levopimaric acid have been synthesized. By a retro-Diels-Alder reaction, the B-ring is cleaved and an aromatic system is formed. Diels-Alder addition of 2-chloroacrylonitrile to abietic acid gives a tetracyclic -chloronitrile (10). Further transformations of this product are described.
Eine friiher beschriebene6) Nebenreaktion beim Zerfall des N-Nitrosoacetanilids in Athanol/ Kaliumacetat, die zur Bildung eines Salzes K[C8H8N303] fuhrte, wurde erneut untersucht. Es ist wahrscheinlich, daD diese Verbindung durch radikalische Addition von N O an die Nitrosogruppe des N-Nitrosoacetanilids und anschlieDende Reduktion entsteht. Das Kaliumsalz und ein entsprechendes Silbersalz werden in fjbereinstimmung mit spektroskopischen Daten als Salze des N-Nitroso-N-(N-phenylacetamido)hydroxylamins (7) formuliert. Die NMR-Linienformanalyse gestattet die Messung einer Rotationsschwelle mit AGf = 16.0 und AGO = 0.6 kcal/mol. Aromatic Diazonium Salts, VI"; Nitrosoacylamines and Diazoesters. XIV'' A New Reaction Mode of N-NitrosoacetanilideA side reaction in the decomposition of N-nitrosoacetanilide in ethanol/potassium acetate, which has been described to produce a salt K[C8H8N3O3l6), was reinvestigated. It is probable that this compound is formed by a free radical addition of NO to the nitroso group of N-nitrosoacetanilide and subsequent reduction. The potassium salt and the corresponding silver salt are considered to be derived from N-nitroso-N-(N-pheny1acetamido)hydroxylamine (7) in agreement with spectroscopic data. Dynamic n. m. r. allows to measure a rotation process with AGf = 16.0 and AG" = 0.6 kcal/mole. N-Nitrosoacetanilid (1) hat seit seiner erstmaligen Herstellung im Jahre 1876 bis zum heutigen Tag durch die Vielfalt seiner Reaktivitat zahlreiche Untersuchungen angeregt 3* ' ).
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