Editorial [Português], v. 6, n. 2

Editorial note Volume 6 Issue 2

editorial note volume 6 issue 2

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4-Bromo-N 2,N 2,N 6,N 6-tetra­ethyl­pyridine-2,6-dicarboxamide

The title compound, C(15)H(22)BrN(3)O(2), consists of a pyridine ring with a bromine atom in the para position and two diethyl-amide groups in the ortho positions of the ring. Despite the positions of the three substituents on the pyridine ring, the mol-ecule does not exhibit either local or crystallographic twofold symmetry as the two diethyl-amido units exhibit significantly different N(py)-C...

N 2,N 2,N 6,N 6-Tetra­kis(2,3,4,5,6-penta­fluoro­benzo­yl)pyridine-2,6-diamine

The title compound, C(33)H(3)F(20)N(3)O(4), is a highly fluorinated organic imide that was isolated as an unexpected product from the reaction of 2,6-diamino-pyridine with 2,3,4,5,6-penta-fluoro-benzoyl chloride in a 1:2 molar ratio. The mol-ecule is located on a twofold axis and one of its symmetry-independent 2,3,4,5,6-penta-fluoro-benzoyl groups is disordered over two sets of sites, the occu...

$n$-cocoherent rings‎, ‎$n$-cosemihereditary rings and $n$-V-rings

 Let $R$ be a ring‎, ‎and let $n‎, ‎d$ be non-negative integers‎. ‎A right $R$-module $M$ is called $(n‎, ‎d)$-projective if $Ext^{d+1}_R(M‎, ‎A)=0$ for every $n$-copresented right $R$-module $A$‎. ‎$R$ is called right $n$-cocoherent if every $n$-copresented right $R$-module is $(n+1)$-coprese-nted‎, ‎it is called a right co-$(n,d)$-ring if every right $R$-module is $(n‎, ‎d)$-projective‎. ‎$R$...