On the Hydrogen Bonding of Succinimide Derivatives: Crystal Structure of 3(4-Pyridil-methyl)amino-pyrrolidine-2,5-dione

The structure of 3(4-pyridil-methyl)amino-pyrrolidine-2,5-dione has been established by X-ray crystallography from diffractometer data with an F2 refinement to R = 0.0526 for 1999 observed reflections. The close packing of orthorhombic crystals space group Pbca (No. 61) with a = 11.595(4), b = 8.325(1), c = 20.452(4) Å, V = 1974.2(8) Å3, Z = 8, Dc = 1.381 Mg/m3, m = 0.824 mm–1 is built of herringbone-like molecular layers folded along the c axis and fused together by infinite chains of NH⋅⋅⋅O and NH⋅⋅⋅N hydrogen bonds perpendicular to one another. This prompted us to review and characterize the hydrogen bond networks formed by succinimides possessing an unsubstituted >NH group by the use of the Cambridge Structural Database (CSD), and our own earlier structure determinations. The common motifs of the hydrogen bond systems are analyzed using graph descriptions suggested by M. C. Etter. The influence of the hydrogen bonds on molecular close packing is also discussed

Obilježja procesa obrade na horizontalnoj tračnoj pili trupčari pri piljenju zamrznute bukovine

The paper presents the research results of process characteristics during cutting beech prisms on horizontal log band saw type Mebor HTZ–1000. The band saw blades were equipped with swaged teeth and stellited teeth. The power consumption, tool wear resistance, surface roughness and variation of board thickness during 6000 m sawn prism length were studied. All studied parameters were monitored during the tool life-circle (from sharpening to loosing its sawing capability). Wearing process was monitored as a function of cutting length. The cutting edge modifi cation, i.e. its wearing affecting energetic demands during sawing process as well as the surface quality and dimension accuracy of produced work piece was monitored, too. Based on cutting edge wear process and its effect on the above mentioned sawing process parameters, the optimal period of saw band replacement with a new or sharpened one was determined. Based on measured parameters, it was possible to determine which type of band saw tooth is recommended for cutting frozen beech.U radu se iznose rezultati istraživanja obilježja procesa piljenja bukovih prizmi na horizontalnoj tračnoj pili trupčari proizvođača Mebor, model HTZ-1000. Za piljenje su primijenjeni listovi pila sa stlačenim i stelitiranim zubima. Proučavana je snaga potrebna za piljenje, postojanost alata, hrapavost obrađene plohe i odstupanje debljine piljenica od nominalne dimenzije, i to tijekom piljenja prizmi ukupne duljine 6000 m. Svi proučavani parametri praćeni su tijekom vremena postojanosti pojedinog lista pile. Proces trošenja zubi lista pile promatran je kao funkcija duljine puta zahvata tijekom piljenja. Također je analiziran utjecaj postupnog zatupljivanja zubi lista pile na energiju potrebnu za piljenje, na kvalitetu obrađene plohe i na odstupanje dimenzija piljenica s obzirom na nominalne vrijednosti. Uzimajući u obzir proces zatupljivanja zubi lista pile i utjecaj na promatrane parametre obrade, određeno je optimalno vrijeme zamjene lista pile. Na temelju izmjerenih parametara zaključeno je koji je način pripreme zubi pile preporučljiv za piljenje zamrznute bukovine

PartiaI Syntheses of 21,27 -Bisnordemissidine from Epiandrosterone and Dehydroepiandrosterone Acetates. Crystal and Molecular Structure of 21,27 -Bisnordemissidine Hydrobromide

Stereoselective syntheses of 21,27-bisnordemissidine from epiandrosterone acetate (1) and dehydroepiandrosterone acetate (la) are described in this work. These syntheses involve in sequence: a) stereospecific addition of «-picolyl-Iithium to the C-17 carbonyl group of 1 (la); b) regio- and chemoselective 17,20-dehydration of the formed diol 2 (2a) leading to 3~-acetoxy-17-picolinylidene- -5a-androstane (3) or the corresponding derivative 3a; c) regiospecific allylic oxidation of C-16 in 3 (3a) by Se02 to 4 and chromic acid oxidation to the crucial intermediates (5a-5d); d) stereospecific intramolecular reductive cyclization reaction of 5a-5d, under carefully chosen reaction conditions, leading to 3~-acetoxy- -21,27-bisnor-5a-solanidane (6); e) hydrolysis of 6 with conc. aq. HBr to the target molecule of 21,27-bisnordemissidine hydrobromide (7); and f) alkaline treatment of 6 and 7 with KOH in MeOH affording 21,27-bisnordemissidine (11). The structure of 7 has been unambiguously proved by the appropriate X-ray structural analysis. Detection and isolation of some intermediates and by-products (8, 9 and 10) during catalytic hydrogenation of 5c and 5d pointed to a possible mechanism of the last and crucial step of the synthesis of 21,27-bisnordemissidine

Crystal and Molecular Structure of 3B-Hydroxy-14,15B-epoxy- 5\u27B,14B-card-20,22-enolide (Digirezigenin)

The title compound C23H3204 and its methyl-suberate ester were discovered in Ch\u27an Su, the dried venom of the Chinese toad. Its crystals are orthorhombic, space group P21212i, and quasi- isostructural with those of the related compound digitoxigenin (C23H340 4) . The structure was solved by direct methods and refined by least squares technique to a conventional R index of 0.059 for 2271 unique diffractometer observations. The presence of the rigid 14, 15~-epoxy ring alters considerably the shape of ring D (17E) relative to that in digitoxigenin (14E). However, it has little effect upon the general features of the 14-iso-aethiocholane skeleton and the conformation of the y-lactone ring. The amount of rotation about the C(l 7)-C(20) bond is hardly changed while the distance between the position of the carbonyl O relative to digitoxigenin is only 33.2 pm. The conformation of the title compound is also compared with that of a bufa-20, 22-dienolide (cinobufagin) which also possesses a 14, 15~-oxirane ring

PartiaI Syntheses of 21,27 -Bisnordemissidine from Epiandrosterone and Dehydroepiandrosterone Acetates. Crystal and Molecular Structure of 21,27 -Bisnordemissidine Hydrobromide

Stereoselective syntheses of 21,27-bisnordemissidine from epiandrosterone acetate (1) and dehydroepiandrosterone acetate (la) are described in this work. These syntheses involve in sequence: a) stereospecific addition of «-picolyl-Iithium to the C-17 carbonyl group of 1 (la); b) regio- and chemoselective 17,20-dehydration of the formed diol 2 (2a) leading to 3~-acetoxy-17-picolinylidene- -5a-androstane (3) or the corresponding derivative 3a; c) regiospecific allylic oxidation of C-16 in 3 (3a) by Se02 to 4 and chromic acid oxidation to the crucial intermediates (5a-5d); d) stereospecific intramolecular reductive cyclization reaction of 5a-5d, under carefully chosen reaction conditions, leading to 3~-acetoxy- -21,27-bisnor-5a-solanidane (6); e) hydrolysis of 6 with conc. aq. HBr to the target molecule of 21,27-bisnordemissidine hydrobromide (7); and f) alkaline treatment of 6 and 7 with KOH in MeOH affording 21,27-bisnordemissidine (11). The structure of 7 has been unambiguously proved by the appropriate X-ray structural analysis. Detection and isolation of some intermediates and by-products (8, 9 and 10) during catalytic hydrogenation of 5c and 5d pointed to a possible mechanism of the last and crucial step of the synthesis of 21,27-bisnordemissidine

Šuplji drveni stupovi i njihovo spajanje metalnim okovima

Wood is a competitive material to metal and concrete in the production of bearing members. These wooden bearing members are increasingly applied in building constructions. By reason of its natural character and properties, this material improves the architectural look of the structure, and hence it is suitable for use in different constructions. Design feature – hollow wooden post is produced by gluing 12 lamellas with trapezoidal cross-section, furnished with slip feather and groove. Each lamella side is cut at an angle of 15° in order to achieve a closed circle in its cross-section. Hollow wooden post is especially made of spruce timber. Wood–steel structural joints between individual structural members have a very important role in wooden structural constructions.U proizvodnji nosivih elemenata u graditeljstvu drvo je konkurentan materijal metalu i betonu. Uporaba drvenih nosača je u porastu. Radi njihova prirodnog izgleda i svojstava drva kao materijala, drvni nosači oplemenjuju arhitektonske konstrukcije i zbog toga se sve češće upotrebljavaju u raznim nosivim konstrukcijama. Šuplji drveni stup proizvodi se sljepljivanjem 12 lamela trapezoidnog presjeka, pri čemu je spajanje izvedeno utorom i perom. Svaka stranica lamele odrezana je pod kutom od 15°, a njihovim se spajanjem dobiva gotovo kružni poprečni presjek stupa. Takvi se stupovi izrađuju od smrekova drva. U drvenim nosivim konstrukcijama važnu ulogu imaju metalni okovi koji služe za povezivanje drvenih nosivih elemenata

On the Hydrogen Bonding of Succinimide Derivatives: Crystal Structure of 3(4-Pyridil-methyl)amino-pyrrolidine-2,5-dione

The structure of 3(4-pyridil-methyl)amino-pyrrolidine-2,5-dione has been established by X-ray crystallography from diffractometer data with an F2 refinement to R = 0.0526 for 1999 observed reflections. The close packing of orthorhombic crystals space group Pbca (No. 61) with a = 11.595(4), b = 8.325(1), c = 20.452(4) Å, V = 1974.2(8) Å3, Z = 8, Dc = 1.381 Mg/m3, m = 0.824 mm–1 is built of herringbone-like molecular layers folded along the c axis and fused together by infinite chains of NH⋅⋅⋅O and NH⋅⋅⋅N hydrogen bonds perpendicular to one another. This prompted us to review and characterize the hydrogen bond networks formed by succinimides possessing an unsubstituted >NH group by the use of the Cambridge Structural Database (CSD), and our own earlier structure determinations. The common motifs of the hydrogen bond systems are analyzed using graph descriptions suggested by M. C. Etter. The influence of the hydrogen bonds on molecular close packing is also discussed

Dicyclo­hexyl­ammonium 3-[(hy­droxy­meth­yl)carbamo­yl]propano­ate

The title compound, C12H24N+·C5H8NO4 −, contains one dicyclo­hexyl­ammonium cation and one 3-[(hy­droxy­meth­yl)carbamo­yl]propano­ate anion in the asymmetric unit. In the crystal, the ions are linked by inter­molecular N—H⋯O and O—H⋯O hydrogen bonds, forming chains propagating along [100]