Investigation using13C and15N CP MAS NMR of potential solid state tautomerism of some indolinones

A¹³C and¹⁵N CP MAS NMR study is reported for seven molecules and the results are compared with those previously obtained from solution NMR. The close agreement between the two sets of results show that the tautomeric equilibria found in solution and the solid state are the same for the compounds investigated. In all cases formA is found to be essentially the only one present. An X-ray diffraction study is presented for a molecule which is a model for formA.     

Nitrogen and carbon NMR of some benzofuroxans

¹⁵N and ¹⁴N NMR spectra show that there is no valence tautomerism involving the nitro group in nitro derivatives of benzofuroxan systems and that the N-oxide function has a fixed position in the furoxan ring. Carbon chemical shifts of molecules with one, two or three furoxan rings attached to a benzene ring reveal additivity of effects which makes possible a complete and unambiguous assignment of the shifts.     

An aromatic iodination method, with iodic acid used as the only iodinating reagent

Benzene, halobenzenes, and a number of more or less deactivated arenes,including nitrobenzene, readily reacted in anhydrous HIO3/AcOH/Ac2O/conc. H2SO4 mixtures to probably give ArIO2 intermediates or other hypervalent species (not isolated). The final reaction mixtures were poured into excess aq. Na2SO3 solution (a reductant) to give the purified iodinated products in 39-83% yields.     

Structural studies on some 1,3,5,7-tetraazabicyclo-[3.3.1]-nonane derivatives

From a study of the ¹H NMR spectra of a number of 3,7-disubstituted derivatives of 1,3,5,7-tetraazabicycio - [3.3.1] - nonane it is concluded that these molecules exist in either chair-chair or flattened chair-chair conformations. The derivatives containing COCH₃ and NO substitutents have room temperature spectra consistent with restricted rotation about their NC and NN bonds respectively. High temperature spectra reveal an activation energy, for the rotational barrier of the NC bond in the diacetyl derivative, of 23±2K.Cal/mol.     

15N NMR spectroscopy of some azines

¹⁵N NMR shielding data are presented for 56 cyclic azines in 0.5 M dimethyl sulfoxide solutions with 0.01 M increments of Cr(acac)₃ added for each nitrogen atom in the molecules. For the polyazines, the ¹⁵N signal assignments were based on ²J(NH) interactions and some INDO/S-SOS shielding calculations. The effects of α-, β- and γ-methyl and conjugated ring substitution on nitrogen shielding are presented and discussed, as are the influences arising from fusion with alicyclic and aromatic rings at various positions. The effects of a second nitrogen atom on the shielding of the first one are shown to be critically dependent on both their relative positions and on the position of fusion of conjugated ring systems.     

Lp + Lq and Lp ∩ Lq are not isomorphic for all 1 ≤ p,q ≤ ∞, p ≠ q

We prove that if $1\le p,q\le \infty$, then the spaces $L_p+L_q$ and $L_p\cap L_q$ are isomorphic if and only if $p=q$. In particular, $L_2+L_{\infty }$ and $L_2\cap L_{\infty }$ are not isomorphic, which is an answer to a question formulated in [2].