Pseudopolymorphism: occurrences of hydrogen bonding organic solvents in molecular crystals

Multi-point recognition with strong and weak hydrogen bonds between solvent and solute molecules facilitates the retention of organic solvents in crystals

Efektivitas Weblog dan Facebook Terintegrasi untuk Pembelajaran Virtual

Saat ini, banyak mahasiswa menghabiskan waktu mereka di internet. Mereka melakukan kegiatan seperti membuat blog, mengunduh, mengunggah, chatting, dan berinteraksi melalui facebook. Mahasiswa sekarang ini hidup dengan teknologi. Penelitian menunjukkan bahwa weblog dan facebook berpotensi mendukung belajar dan mengajar. Guru dan pendidik menggunakan kegiatan tersebut untuk meningkatkan kualitas belajar. Penelitian ini bertujuan untuk mengetahui efektivitas weblog dan facebook ketika digunakan secara integratif untuk melengkapi pembelajaran. Penelitian ini menggunakan metode kuantitatif deskriptif. Data dikumpulkan dari halaman-halaman facebook yang diamati dari responden yang mengambil mata kuliah Introduction of Second Language Acquisition (SLA). Data kemudian dideskripsikan dan dianalisis. Temuan penelitian menunjukkan bahwa weblog dan facebook dapat digunakan secara efektif untuk melengkapi kegiatan belajar

Expeditious synthetic route to B-ring functionalised 2-oxa-steroids: Synthesis of 17-ethylenedioxy-6a-hydroxy-2-oxa-4-androsten-3-one as key synthon

1113-111

Isostructurality in crystalline oxa-androgens: a case of C-O-···O and C-H···O interaction mimicry and solid solution formation

A C-H···O interaction in 2-oxa-4-androstene-3,17-dione is replaced by a C-O-H···O hydrogen bond in the isostructural 6a-hydroxy analogue, and these compounds form a binary solid solution, showing the similarity of these two crystal structures

Odessa's Intellectuals In the 1920s: the activities of the All-Ukrainian Committee for the Promotion of Scientists

У статті аналізуються усі сфери суспільного життя в Україні у перше десятиліття більшовицького режиму. Досліджується основні напрямків діяльності Всеукраїнського комітету сприяння вченим у 1920 рр. у великому науковому центрі України – Одесі.В статье анализируются все сферы общественной жизни в Украине в первое десятилетие большевистского режима. Исследуется основные направления деятельности Всеукраинского комитета содействия ученым в 1920 в большом научном центре Украины - Одессе.The article analyzes all spheres of public life in Ukraine in the first decade of the Bolshevik regime. The main directions of activity of the All-Ukrainian Committee for the Facilitation of Scientists in 1920 in the large scientific center of Ukraine - Odessa were investigated

Multiple molecules in the crystallographic asymmetric unit. Self host-guest and doubly interpenetrated hydrogen bond networks in a pair of keto-bisphenols

The presence of two molecules in the crystallographic asymmetric unit in a pair of closely related keto-bisphenols that differ by a methyl substituent only, leads to open frameworks that fill space through self-inclusion in one case, and through interpenetration in the other

Evidence for the characterisation of the C-H …∏ interaction as a weak hydrogen bond: toluene and chlorobenzene solvates of 2,3,7,8-tetraphenyl-1,9,10-anthyridine

The crystal structures of the toluene and chlorobenzene solvates of 2,3,7,8-tetraphenyl-1,9,10-anthyridine are nearly identical save for differences in the mode of solvent inclusion; these differences have an important bearing on the nature of the C-H … ∏ interactions in these structures

Engineering of an octupolar non-linear optical crystal: tribenzyl isocyanurate

The title compound has a C-H···O hydrogen bond-mediated trigonal network structure that leads to octupolar NLO behaviour in the solid state

Interplay of strong and weak hydrogen bonding in molecular complexes of some 4,4'-disubstituted biphenyls with urea, thiourea and water

The crystal chemistry and engineering of a new family of host-guest complexes is described. 4,4'-Dicyanobiphenyl (DCBP) forms a 1:1 complex, 1 with urea wherein the DCBP host forms large hexagonal channels via C-H···N hydrogen bonds and the urea guest molecules are arranged in N-H···O ribbons which fit completely within the host channels. By analogy, 4,4'-bipyridine N,N'-dioxide (BPNO) was selected as a molecule that can form a corresponding C-H…O based channel. BPNO forms complexes with urea (2), thiourea (3) and water (4). Structures 2 and 3 provide some points of comparison with the structure of 1 but are not fully equivalent to it. In structure 4, the smaller guest water is able to fit neatly within the smaller hexagonal channel of BPNO and in this sense, the degree of structural predictability is satisfactory. To obtain another structure similar to that of 1, 4,4'-dinitrobiphenyl (DNBP) was identified as an alternative host compound. This choice was justified by the structure of its 1:1 complex, 5 with urea. In all cases, the guest molecules interact with each other via strong hydrogen bonds and form an essential template for the weak hydrogen bonded assembly of the host network structure but the latter is still of some significance. One finds consequently, in complexes 1-5, a constructive interplay of strong and weak hydrogen bonds

2,6-dibenzoyl-1,4-benzoquinone

Publisher's version/PDFIn contrast to the stacking characteristic of quinones, the title compound, C[subscript 20]H[subscript 12]O[subscript 4], forms a two-dimensional network of C--H...O hydrogen bonds. The molecule has an unsymmetrical butterfly shape with the two benzoyl O atoms lying out of the plane of the quinonoid ring. The unusual conformation is a result of the crystal packing and the numerous weak hydrogen bonds