Summary. Secondary deactivated aliphatic diazo compounds (diazo-ketones R-CO-CN,-R'; diazo-esters ROOC-CN,-R'; 1,1, I-trifluoro-2-diazopropane) are hydrolyscd by the A -S E~ mechanism comprising rate determining protonation of the substrate, followed by decomposition. Product analysis shows that the dccomposition of the secondary diazonium ions is monomolccular, without intervention of a nucleophile.The corresponding primary diazo compounds (R-CO-CHN,, ROOC-CHN, and CF,-CHN,) are hydrolysed by the A-2 mechanism comprising preequilibrium protonation; the primary diazonium ion reacts with a nucleophilc in a bimolecular displaccmcnt step .The only exception observcd is found in p-nitrophenyl-diazomethane, which follows A -S E~ mechanism.The observations are discussed in terms of the stability of the corrcsponding secondary resp. primary cc-keto-carbonium ions.Primare Diazoketone R-CO-CHN, werden bei der sauren Hydrolyse rasch und reversibel protoniert, worauf das gebildete Diazonium-Ion im geschwindigkeitsbestimmenden Schritt zu den Produkten zersetzt wird Wir fanden, dass auch anderweitig desaktivierte Diazoalkane wie 2,2,2-Trifluordiazoathan CF3-CHN, rasch und reversibel protoniert werden. Der Nachweis der Reversibilitat erfolgte wie in anderen Fallen [a]

On the basis of our results we can draw the conclusion that silicon and germanium differ from carbon by the possibility of using the vacant d-orbitals, and by lower electronegativity and higher polarizability. The difference between germanium and silicon is relatively small, as far as electronegativity is concerned, and it is somewhat more important in the case of polarizability. As far as the differences in ability to form bonds of the ( p + d) z type are concerned, no general comparison can be made: while, from this point of view, there is no substantial difference between the Si-C,H, and Ge-C,H, bonds, in the case of other bond types (e. g. bonds with oxygen) these differences are very marked.

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Dedicated to Prof. Tino Giiumann on the occasion of his 6OCh birthday (25.V11.85) ~~ 4-Aryl-2,3-dioxobutyrdmide hydrates 1 undergo the benzil-benzilic acid rearrangement to form (substituted) benzyltartronate monoamides 2. For compound l a (Ar = Ph), it is demonstrated by isotopic labelling that the reaction occurs exclusively by migration of the CONH, group. Kinetic measurements with la-c and with the cyclic amide quinisatine 6 show that the rearrangement of the carboxamide group, proceeding via an alkali-catalysed step, can reach a plateau in the kOb,./[OH-] diagram (cf: the Fig.), due to complete formation of a mono-anion, and a further increase of rate attributable to the rearrangement of a bis-anion. Comparisons suggest that rearrangements involving an amide group are slower than those involving an ester group, and that, for this effect (as for others), the pre-equilibrium deprotonation of the hydrate is more important than a specific migration tendency.