scholarly journals ATOMIC STRUCTURES OF GLUCOSE, FRUCTOSE AND SUCROSE AND EXPLANATION OF ANOMERIC CARBON

2014 ◽  
Author(s):  
Raji Heyrovska
Keyword(s):  
Double Bond ◽  
Single Bond ◽  
Open Chain ◽  
Bond Lengths ◽  
Atomic Structures ◽  
Anomeric Carbon ◽  
First Time ◽  
Atomic Radii

Presented here are the structures of three biologically important sweet sugars, based on the additivity of covalent atomic radii in bond lengths. The observed smaller carbon-oxygen distances involving the 'anomeric' carbons of the open chain hexoses are explained here, for the first time, as due to the smaller covalent double bond radii of carbon and oxygen than their single bond radii in the cyclic forms and in sucrose. The atomic structures of all the three carbohydrates, drawn to scale in colour, have been presented here also for the first time.

scholarly journals Crystal structure ofN′′-benzyl-N′′-[3-(benzyldimethylazaniumyl)propyl]-N,N,N′,N′-tetramethylguanidinium bis(tetraphenylborate)

2015 ◽  
Vol 71 (12) ◽  
pp. o1086-o1087
Author(s):  
Ioannis Tiritiris ◽  
Willi Kantlehner
Keyword(s):  
Crystal Structure ◽  
Double Bond ◽  
Positive Charge ◽  
Planar Geometry ◽  
Methyl Groups ◽  
Two Dimensional ◽  
Single Bond ◽  
Double Bond Character ◽  
Bond Lengths ◽  
Bond Character

In the crystal structure of the title salt, C24H38N42+·2C24H20B−, the C—N bond lengths in the central CN3unit of the guanidinium ion are 1.3364 (13), 1.3407 (13) and 1.3539 (13) Å, indicating partial double-bond character. The central C atom is bonded to the three N atoms in a nearly ideal trigonal–planar geometry and the positive charge is delocalized in the CN3plane. The bonds between the N atoms and the terminal methyl groups of the guanidinium moiety and the four C—N bonds to the central N atom of the (benzyldimethylazaniumyl)propyl group have single-bond character. In the crystal, C—H...π interactions between the guanidinium H atoms and the phenyl C atoms of the tetraphenylborate ions are present, leading to the formation of a two-dimensional supramolecular pattern parallel to theacplane.

scholarly journals N,N,N′,N′-Tetramethyl-N′′-[2-(trimethylazaniumyl)ethyl]guanidinium bis(tetraphenylborate) acetone disolvate

IUCrData ◽  
2016 ◽  
Vol 1 (2) ◽  
Author(s):  
Ioannis Tiritiris ◽  
Willi Kantlehner
Keyword(s):  
Double Bond ◽  
Positive Charge ◽  
Planar Geometry ◽  
Two Dimensional ◽  
Single Bond ◽  
Asymmetric Unit ◽  
Bond Lengths ◽  
Phenyl Rings ◽  
Solvent Molecules ◽  
Bond Character

The asymmetric unit of the title solvated salt, C10H26N42+·2C24H20B−·2C3H6O, comprises one cation, two tetraphenylborate ions and two acetone solvent molecules. The N and methyl C atoms of the terminal trimethylammonium group are disordered over two sets of sites, with a refined occupancy ratio of 0.846 (3):0.154 (3). The C—N bond lengths in the central C3N unit of the guanidinium ion range between 1.3308 (16) and 1.3508 (16) Å, indicating a degree of double-bond character. The central C atom is bonded to the three N atoms in a nearly ideal trigonal–planar geometry and the positive charge is delocalized in the CN3plane. The C—N bond lengths in the terminal trimethylammonium group have values close to that of a typical single bond, and the second positive charge is localized there. In the crystal, the guanidinium ion is connected by N—H...O and C—H...O hydrogen bonds with the acetone molecules. C—H...π interactions are present between the guanidinium H atoms and the phenyl rings of the tetraphenylborate ions, leading to the formation of a two-dimensional supramolecular pattern along thebcplane.

scholarly journals Crystal structure of 2-bromo-3-dimethylamino-N,N,N′,N′,4-pentamethyl-4-(trimethylsilyloxy)pent-2-eneamidinium bromide

2015 ◽  
Vol 71 (12) ◽  
pp. o1061-o1062
Author(s):  
Ioannis Tiritiris ◽  
Ralf Kress ◽  
Willi Kantlehner
Keyword(s):  
Crystal Structure ◽  
Double Bond ◽  
Bond Length ◽  
Single Bond ◽  
Charge Delocalization ◽  
Double Bond Character ◽  
Bond Lengths ◽  
Bromide Ions ◽  
Bond Character

The reaction of the orthoamide 1,1,1-tris(dimethylamino)-4-methyl-4-(trimethylsilyloxy)pent-2-yne with bromine in benzene, yields the title salt, C15H33BrN3OSi+·Br−. The C—N bond lengths in the amidinium unit are 1.319 (6) and 1.333 (6) Å, indicating double-bond character, pointing towards charge delocalization within the NCN plane. The C—Br bond length of 1.926 (5) Å is characteristic for a C—Br single bond. Additionally, there is a bromine–bromine interaction [3.229 (3) Å] present involving the anion and cation. In the crystal, weak C—H...Br interactions between the methyl H atoms of the cation and the bromide ions are present.

scholarly journals Identification, synthesis and mass spectrometry of a macrolide from the African reed frog Hyperolius cinnamomeoventris

2016 ◽  
Vol 12 ◽  
pp. 2731-2738 ◽  
Author(s):  
Markus Menke ◽  
Pardha Saradhi Peram ◽  
Iris Starnberger ◽  
Walter Hödl ◽  
Gregory FM Jongsma ◽  
...  
Keyword(s):  
Mass Spectrum ◽  
Double Bond ◽  
Fragmentation Pathway ◽  
Ring Closing Metathesis ◽  
Grubbs Catalyst ◽  
Open Chain ◽  
Naturally Occurring ◽  
Products Analysis ◽  
First Time ◽  
Gular Glands

The contents of the gular glands of the male African reed frog Hyperolius cinnamomeoventris consist of a mixture of aliphatic macrolides and sesquiterpenes. While the known macrolide gephyromantolide A was readily identified, the structure of another major component was suggested to be a tetradecen-13-olide. The synthesis of the two candidate compounds (Z)-5- and (Z)-9-tetradecen-13-olide revealed the former to be the naturally occurring compound. The synthesis used ring-closing metathesis as key step. While the Hoveyda–Grubbs catalyst furnished a broad range of isomeric products, the (Z)-selective Grubbs catalyst lead to pure (Z)-products. Analysis by chiral GC revealed the natural frog compound to be (5Z,13S)-5-tetradecen-13-olide (1). This compound is also present in the secretion of other hyperoliid frogs as well as in femoral glands of male mantellid frogs such as Spinomantis aglavei. The mass spectra of the synthesized macrolides as well as their rearranged isomers obtained during ring-closing metathesis showed that it is possible to assign the location of the double bond in an unsaturated macrolide on the basis of its EI mass spectrum. The occurrence of characteristic ions can be explained by the fragmentation pathway proposed in the article. In contrast, the localization of a double bond in many aliphatic open-chain compounds like alkenes, alcohols or acetates, important structural classes of pheromones, is usually not possible from an EI mass spectrum. In the article, we present the synthesis and for the first time elucidate the structure of macrolides from the frog family Hyperoliidae.

scholarly journals 3-Methyl-4,5-dihydrooxazolium tetraphenylborate

2014 ◽  
Vol 70 (3) ◽  
pp. o325-o325
Author(s):  
Ioannis Tiritiris ◽  
Stefan Saur ◽  
Willi Kantlehner
Keyword(s):  
Double Bond ◽  
Bond Length ◽  
Phenyl Ring ◽  
Single Bond ◽  
Charge Delocalization ◽  
Double Bond Character ◽  
Bond Lengths ◽  
Bond Character

In the cation of the title salt, C4H8NO+·C24H20B−, the C—N bond lengths are 1.272 (2), 1.4557 (19) and 1.4638 (19) Å, indicating double- and single-bond character, respectively. The C—O bond length of 1.3098 (19) Å shows that double-bond character and charge delocalization occurs within the NCO plane of the cation. In the crystal, a C—H...π interaction is present between the methylene H atom of the cation and one phenyl ring of the tetraphenylborate ion. The latter forms an aromatic pocket in which the cation is embedded.

scholarly journals N,N,N′,N′,N′′-Pentamethyl-N′′-[3-(trimethylazaniumyl)propyl]guanidinium bis(tetraphenylborate)

2013 ◽  
Vol 69 (2) ◽  
pp. o292-o292 ◽  
Author(s):  
Ioannis Tiritiris
Keyword(s):  
Crystal Structure ◽  
Double Bond ◽  
Positive Charge ◽  
Planar Geometry ◽  
Methyl Groups ◽  
Single Bond ◽  
Double Bond Character ◽  
Bond Lengths ◽  
Phenyl Rings ◽  
Bond Character

In the crystal structure of the title salt, C12H30N42+·2C24H20B−, the C—N bond lengths in the central CN3unit of the guanidinium ion are 1.3388 (17), 1.3390 (16) and 1.3540 (17) Å, indicating partial double-bond character in each. The central C atom is bonded to the three N atoms in a nearly ideal trigonal-planar geometry and the positive charge is delocalized in the CN3plane. The bonds between the N atoms and the terminalC-methyl groups of the guanidinium moiety, all have values close to a typical single bond [1.4630 (16)–1.4697 (17) Å]. C—H...π interactions are present between the guanidinium H atoms and the phenyl C atoms of one tetraphenylborate ion. The phenyl rings form a kind of aromatic pocket, in which the guanidinium ion is embedded.

scholarly journals 3,3′-[(2-Bromo-1,3-phenylene)bis(methylene)]bis(1-butyl-2,3-dihydro-1H-imidazole-2-selone)

IUCrData ◽  
2017 ◽  
Vol 2 (12) ◽  
Author(s):  
Varsha Rani ◽  
Harkesh B. Singh ◽  
Ray J. Butcher
Keyword(s):  
Double Bond ◽  
Benzene Ring ◽  
Intermolecular Interactions ◽  
Title Compound ◽  
Zigzag Chain ◽  
Side Chains ◽  
Single Bond ◽  
Axis Direction ◽  
Bond Lengths ◽  
Compound C

In the title compound, C22H29BrN4Se2, the two Se atoms are directed in opposite directions with respect to the central benzene ring. The C=Se bond lengths at 1.848 (5) and 1.851 (5) Å are on the long side for a double bond but shorter than expected for a C—Se single bond. In the crystal, Br...Br intermolecular interactions [3.4685 (12) Å] link the molecules into a zigzag chain propagating along theb-axis direction. In addition, there are C—H...Se intermolecular interactions present, linking the chains to form slabs parallel to theabplane. One of the two butyl side chains is disordered over two conformations with occupancies of 0.777 (9) and 0.223 (9).

A Novel Scheme for the Synthesis of 21-Acetoxypregna-1,4,9(11)-triene- 17α,21-diol-3,20-dione from 9α-Hydroxyandrostenedione

2020 ◽  
Vol 16 (5) ◽  
pp. 606-610
Author(s):  
Nguyen T. Diep ◽  
Luu D. Huy
Keyword(s):  
Double Bond ◽  
Chemical Synthesis ◽  
Economic Efficiency ◽  
Final Stage ◽  
Side Chain ◽  
Entire Process ◽  
Drug Synthesis ◽  
First Time

Background: Vietnam currently imports up to 90% of the pharmaceuticals it consumes and 100% of the steroid-based pharmaceuticals. The ability for efficient chemical synthesis of the steroids could create commercial opportunities to address this issue. Synthesis of 21-acetoxypregna-1,4,9(11)- triene-17α,21-diol-3,20-dione is considered a key intermediate in the scheme of steroidal drug synthesis. Previous synthesis attempts of such steroids (corticoids) introduce a double bond at C-1(2) in the final stage of synthesis, which delivers a poor yield and reduces the economic efficiency of the process. Objective: To study and develop a novel and effective method for the synthesis of 21-acetoxypregna- 1,4,9(11)-triene-17α,21-diol-3,20-dione. Methods: Using 9α-hydroxyandrostenedione as a substrate chemical synthesis was performed as follows: pregnane side chain construction at C-17 (acetylene method), introduction of C-1(2) double bond (using SeO2), epimerization of C-17 (via 17-ONO2 ester) and Stork’s iodination. Results: 21-acetoxypregna-1,4,9(11)-triene-17α,21-diol-3,20-dione was prepared from 9α- hydroxyandrostenedione with an improved yield compared to previous attempts. Conclusion: Here, 21-acetoxypregna-1,4,9(11)-triene-17α,21-diol-3,20-dione has been synthesized from 9α-hydroxyandrostenedione based on a novel, effective and commercially feasible scheme. The introduction of the C-1(2) double bond at an earlier stage of the synthesis has increased the economic efficiency of the entire process. For the first time, the indirect epimerization mechanism has been clarified along with the configuration of the C-17 stereo-center which has been confirmed using NOESY data.

The Change in the Raman Spectra of Chloroprene and Isoprene in the Polymerization Process

1943 ◽  
Vol 16 (4) ◽  
pp. 841-847
Author(s):  
A. Gantmacher ◽  
S. Medvedev
Keyword(s):  
Raman Spectrum ◽  
Double Bond ◽  
Raman Spectra ◽  
Polymer Molecule ◽  
Polymerization Process ◽  
High Polymer ◽  
Single Bond ◽  
Double Bonds ◽  
Continuous Background ◽  
Single Bonds

Abstract 1. When chloroprene and isoprene polymerize, besides the frequency characterizing the conjugate double bond in the monomer, there appears a higher frequency corresponding to the isolated double bond in the polymer. In the polymerization process, the intensity of the frequency of the conjugate double bond decreases and the intensity of the frequency of the isolated double bond increases. Because of the increase in the number of single bonds in the polymer, the intensity of the frequency of the single bond 1005 in the polymer is considerably greater than in the monomer. 2. Even in the case of the samples with high polymer contents (greater than 50 per cent), the intensity of the frequency of the conjugate double bond is considerably greater than the intensity of the frequency of the isolated double bond. This is attributable to the fact that part of double bonds disappear during polymerization. 3. The Raman spectra of the chloroprene and isoprene polymers differ essentially from those of the monomers. To characterize the frequencies of vibration in the polymer molecule, it is essential to investigate its Raman spectrum in a medium free of the monomer. 4. The formation of highly polymeric molecules on polymerization does not result in an increase in the intensity of the continuous background in spectrograms.

Sign in / Sign up

Export Citation Format

Share Document