Photoinduced rearrangement of aromatic N-chloroamides to chloroaromatic amides in the solid state: inverted Π(N)-Σ(N) occupational stability of amidyl radicals

We report a solid-state photochemical rearrangement reaction by which aromatic N-chloroamides exposed to UV light or sunlight are rapidly and efficiently converted to chloroaromatic amides. The course, the intermediate (nascent chlorine vs dichlorine) and the outcome of the reaction depend on the excitation (exposure time, wavelength, and intensity) and on inherent structural factors (the directing role of the substituents and, as demonstrated by the different reactivity of two polymorphs of N-chlorobenzanilide, the supramolecular structure). The photolysis of the chloroamides provides facile photochemical access to arylamidyl radicals as intermediates, which in the absence of strong hydrogen bond donors are stabilized in the reactant crystals by C-H/N-Cl···π interactions, thus, providing insight into their structure and chemistry. Thorough theoretical modeling of the factors determinant to the stability and the nature of the spin-hosting orbital evidenced that although the trans-Π(||) state (Np spin) of the amidyls is normally preferred over the trans-Σ(⊥) configuration (Nsp(2) spin), stabilization by aromatic conjugation, steric and geometry factors, as well as by electronic effects from the substituents can decrease the Π-Σ gap in these intermediates significantly, resulting in similar and, in the case of the orthogonal amide-phenyl disposition, even reversed population of the unpaired electron in the two orbitals. Quantitative correlation established that the inverted occupational spin stability and the Π(N)-Σ(N) crossover are collectively facilitated by the conformation, valence angle, and disposition of the amide group relative to the aromatic system. The stabilization and detection of a trans-Σ(⊥) radical was experimentally accomplished by steric locking of the orthogonal trans-amide conformation with double ortho-tert-butyl substitution at the phenyl ring. The effects of the single para-phenyl substituents on the relative occupational stability of the arylamidyl radical states point out to non-Hammett behavior. By including cumulative electronic effects from multiple substitutions, four distinct families of the aromatic amidyl radicals were identified. The Π(∥) state is the most stable structure of the N-phenylacetamidyl radical and of most of the substituted arylamidyls, although the Σ(⊥) and Π(⊥) states can also be stabilized by introducing tert-butyl and nitro groups, respectively.     

On Homotopy Groups of Real Algebraic Varieties and their Complexifications

Let X ₀ be a topological component of a nonsingular real algebraic variety and i:X → X _C is a nonsingular projective complexification of X. In this paper, we will study the homomorphism on homotopy groups induced by the inclusion map i:X ₀ → X _C and obtain several results using rational homotopy theory and other standard tools of homotopy theory.     

trans‐Bis(diethanolamine‐N,O)bis(saccharinato‐N)cadmium(II)

The structure of the title complex consists of isolated [Cd(C₇H₄NO₃S)₂(C₄H₁₁NO₂)₂] units. The Cd²⁺ cation lies on an inversion centre and is octahedrally coordinated by two N,O‐bidentate diethanol­amine (dea) and two N‐bonded saccharinate (sac) ligands [saccharin is 1,2‐benziso­thia­zol‐3(2H)‐one 1,1‐dioxide]. The dea ligands constitute the equatorial plane of the octahedron, forming two five‐membered chelate rings around the Cd^II ion, while the sac ligands are localized at the axial positions. The Cd—N_sac, Cd—N_dea and Cd—O_dea bond distances are 2.3879 (12), 2.3544 (14) and 2.3702 (13) Å, respectively. The H atoms of the free and coordinated hydroxyl groups of the dea ligands are involved in hydrogen bonding with the carbonyl and sulfonyl O atoms of the neighbouring sac ions, while the amine H atom forms a hydrogen bond with the free hydroxyl O atom. The individual mol­ecules are held together by strong hydrogen bonds, forming an infinite three‐dimensional network.     

Phytochemical Analysis of Some Sideritis Species of Turkey

Linearol, foliol, epicandicandiol, siderol and ent-7,18-dihydroxy-15,16-epoxykaurane have been investigated for antibacterial activity test. Highest activity of epicandicandiol has been determined against E-coli.     

Synthesis and Structure of Trans‐bis(ethanolamine)bis(saccharinato)mercury(II)

Trans‐bis(ethanolamine)bis(saccharinato)mercury(II), [Hg(ea)₂(sac)₂], where ea and sac denote the ethanolamine molecule and the saccharinate anion, respectively, crystallizes in the triclinic space group P (No. 2) with a = 9.4651 (5), b = 10.4365 (5), c = 11.9314 (6) Å, α = 84.402 (1)° β = 78.313 (1)°, γ = 75.307 (1)°, Z = 2, V = 1115.11 (10) ų. The structure consists of isolated [Hg(ea)₂(sac)₂] units in which the Hg(II) ion is octahedrally coordinated by two nitrogen and two oxygen atoms of two neutral ea ligands, and two nitrogen atoms of two sac ligands. The ea acts as a bidentate N‐ and O‐donor ligand and occupies the trans positions of the equatorial plane of the coordination octahedron forming a fivemembered chelate ring, while sac behaves as a monodentate N‐donor ligand occupying the axial positions. The average Hg‐N_sac and Hg‐N_ea bond distances are 2.739 (3) and 2.114 (7) Å, respectively. The crystal exhibits extensive hydrogen bonds between the hydroxyl and amine hydrogen atoms of the ea ligands and the sulfonyl, carbonyl and amine groups of the sac ligands.