CO2-Laserinduzierte Isomerisierung von Methylisocyanid

Ohne Zusammenfassung     

Versuche zur Isomerisierung von o-Hydroxyazobenzolen durch UV-Strahlen

Zusammenfassung Es wird der Versuch einercis-trans-Isomerisierung an o-Hydroxyazobenzolen mittels UV-Licht beschrieben.

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The attempedcis-trans-isomerisation of o-hydroxyazobenzenes with UV-light has been described.

     

Isomerisierung von Methoxy- und Carbomethoxysubstituierten Cycloalkyl- und Alken-radikalkationen

The very complex isomerization patterns of methoxy and carbomethoxy substituted cycloalkanes (3- to 7-membered rings) have been investigated using collisional activation, metastable ion characteristics and field ionization kinetics. The extent of isomerization depends on both the ring size and the substituent. Irrespective of the electronic properties of the substituent, ring opening involves exclusively the C-1? C-2 bond whereby linear alkene radical cations are formed. In the case of OCH₃- and COOCH₃ substituents the position of the resulting double bond (terminal or α,β-unsaturated) is determined more by the ring size of the precursor molecules and less by the electronic properties of the substituents. Contrary to these findings alklyl substituted cycloalkanes (3- to 5-membered rings) rearrange exclusively to terminal alkene radical cations. The barrier for double bond isomerization seems to be substantially influenced by substituents.     

Isomerisierung und Ringinversion von Tribenzaspiro[5.5]undecaphanen

For the two possible ring inversions in tribenzaspiro[5.5]undecaphanes—corresponding to the isomerizations79 and97 resp.—no mutual influence is found. Thus the degenerate isomerizations (topomerizations)77 and99 can proceedvia two consecutive (non-concerted) reversals. A ring inversion path similar to that for [2.2]metacyclophane (1) is postulated. The considerable ease of the isomerization of9 as compared to1 can be understood on the basis of thermodynamic arguments.Moreover it is confirmed that the free enthalpy difference G ₃₆₀=3.84 kcal/mol of7 and9 at equilibrium originates almost entirely from the different stabilities of boat and chair shaped benzene rings.These conclusions are drawn from a kinetic study of the thermal isomerization of9 and equilibration experiments in comparison with the corresponding data of1. The activation parameters for the process97 are: G _360isom ^A =26.52 kcal/mole, H _isom ^A =25.35 kcal/mole, S _isom ^A =–3.28 cal/deg·mole (isomerization) and G _360inv ^A =27.03 kcal/mole, H _inv ^A =25.35 kcal/mole, S _inv ^A =–4.67 cal/deg·mol (ring reversal); the corresponding data for the degenerate isomerizations of7 and9—identical with those for the ring reversal in7—were deduced to be G _360inv ^B =30.87 kcal/mole, H _inv ^B =27.50 kcal/mole and S _inv ^B =–9.5 cal/deg·mole.

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Mit 7 Abbildungen

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Herrn Prof.H. Nowotny mit besten Wünschen zum 65. Geburtstag gewidmet.

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7. Mitt.:H. Keller, E. Langer undH. Lehner, Mh. Chem.107, 949 (1976).     

Nickel-katalysierte Isomerisierung von Butadien-Hydrazon-Misch-Oligomeren. Vorläufige Mitteilung

Nickel-catalysed Isomerization of Unsaturated Azocompounds Unsaturated azocompounds, produced by the nickel-catalysed reaction of butadiene with hydrazones, can be isomerized in presence of the same nickel catalyst. The influence of nickel concentration, temperature and structure of the azocompound on this rearrangement is described.     

Copolymerisation von CO2 und Athylenimin

Ohne Zusammenfassung     

Formamidinoylisothiocyanate—II : Isomerisierung,dimerisierung und kondensations-reaktionen von formamidinoylisothiocyanaten

Formamidinoylisothiocyanates isomerize easy and give 3 H-chinazolinthiones-(4). The dimerization of formamidinoylisothiocyanates yields derivatives of s-triazines by 1.4-1′.2′-cycloaddition. Further cycloadditions are possible with phenylisocyanate and hydrogen thiocyanate.Formamidinoylisothiocyanates undergo intermolecular elimination of hydrogen thiocyanate yielding derivatives of chinazolin, which are substituted with amidino-groups.     

Zur molekularen Packung von Acetonitril, Methylisocyanid und Propin in ihren nicht isotypen Kristallstrukturen

Ohne Zusammenfassung

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On the molecular packing of acetonitrile, methylisocyanide and propine in their non-isotypic crystal structures