Photo, thermal and chemical degradation of riboflavin

• Muhammad Ali Sheraz,
• Sadia Hafeez Kazi,
• Sofia Ahmed,
• Zubair Anwar and
• Iqbal Ahmad

Beilstein J. Org. Chem. 2014, 10, 1999–2012, doi:10.3762/bjoc.10.208

• been identified that affect the stability of RF. These factors include radiation source, its intensity and wavelength, pH, presence of oxygen, buffer concentration and ionic strength, solvent polarity and viscosity, and use of stabilizers and complexing agents. A detailed review of the literature in

• viscosity The rate of RF photolysis is affected by solvent polarity, which causes changes in the conformation of the ribityl side chain to undergo degradation [83]. RF shows higher photostability in less polar solvents [96]. When RF was irradiated anaerobically in alcohols and alcohol/water mixtures, a

• , dioxane and its mixtures with water, ethanol and pyridine [96][97][98]. The photodegradation of RF has been found to be more rapid in organic solvents as compared to aqueous solutions [97][99]. This could be linked to the physical properties of the solvents such as polarity, dielectric constant, viscosity

Efficient CO₂ capture by tertiary amine-functionalized ionic liquids through Li⁺-stabilized zwitterionic adduct formation

• Zhen-Zhen Yang and
• Liang-Nian He

Beilstein J. Org. Chem. 2014, 10, 1959–1966, doi:10.3762/bjoc.10.204

• absorbed per mol of base) had a CO2 capacity below 1:1 stoichiometry expected from the proposed mechanism (Scheme 1c), owing to highly increased viscosity after CO2 absorption (Table 1, entries 12 and 13). Compared on a weight basis, a CO2 capacity of 5.0 wt % to 8.0 wt % was obtained with ILs from neutral

Supercritical carbon dioxide: a solvent like no other

• Jocelyn Peach and
• Julian Eastoe

Beilstein J. Org. Chem. 2014, 10, 1878–1895, doi:10.3762/bjoc.10.196

• of polar and ionic species and attempts to enhance scCO2 viscosity. Keywords: CO2 chemistry; microemulsion; self-assembly; supercritical CO2; surfactant; viscosity; Introduction In this day and age, sustainability and renewability are watchwords. This includes focus within the scientific community

• properties ordinarily required for an effective solvent, with a lower viscosity, dielectric constant [26][27] and surface tension in comparison to other common reference solvents. Also, as CO2 is a linear molecule with no net dipole moment there is significant difficulty dissolving polar and ionic species

• managed and controlled; both of these techniques would be both economically and technically more viable if the viscosity of CO2 used could be increased (leading to a reduction of viscous fingering during EOR and giving generally more overall control in CCS). The physicochemical properties of CO2 have thus

A promising cellulose-based polyzwitterion with pH-sensitive charges

• Thomas Elschner and
• Thomas Heinze

Beilstein J. Org. Chem. 2014, 10, 1549–1556, doi:10.3762/bjoc.10.159

• aqueous solution or the cleavage of carbamate moieties from the polymer backbone during acidic and basic treatment. However, the ratio between amino and carboxylic groups is balanced. In addition, the IP was proofed by rheology. The IP is indicated by a minimum of the relative viscosity of a

• dynamic light scattering (DLS) and obtained by the cumulants method assuming spherical shape. Each measurement was repeated at least two times. Manual potentiometric titrations were performed with a SevenMulti™ pH meter (Mettler Toledo, Gießen, Germany). The viscosity of the polymer solutions was measured

• with a Haake Mars II cone-plate rheometer (Thermo Scientific, Schwerte, Germany) in controlled rate mode at 20 °C. Shear rates were varied from 0.1 to 1000 s−1 in a cycle of increasing and decreasing shear rate over 5 min. The linear range was extrapolated to zero shear viscosity. Syntheses Synthesis

Synthesis and solvodynamic diameter measurements of closely related mannodendrimers for the study of multivalent carbohydrate–protein interactions

• Yoann M. Chabre,
• Alex Papadopoulos,
• Alexandre A. Arnold and
• René Roy

Beilstein J. Org. Chem. 2014, 10, 1524–1535, doi:10.3762/bjoc.10.157

• × rs) can be calculated using the Stokes–Einstein equation and the viscosity of pure D2O (Table 1). As expected, nonavalent conjugates 12, 17, and 21 presented solvodynamic diameters in the range of roughly 3 nm when considering the decay of distinctive and common H-5 signals. These values remained

An economical and safe procedure to synthesize 2-hydroxy-4-pentynoic acid: A precursor towards ‘clickable’ biodegradable polylactide

• Quanxuan Zhang,
• Hong Ren and
• Gregory L. Baker

Beilstein J. Org. Chem. 2014, 10, 1365–1371, doi:10.3762/bjoc.10.139

• 5. The alkylation step was optimized and it can be conducted with an enolate concentration of 4 up to 0.25 M in dioxane (Table 1). The attempt with higher enolate concentration was not smooth due to the increased viscosity of the reaction mixture and thus low efficiency of stirring, even with a

The influence of intraannular templates on the liquid crystallinity of shape-persistent macrocycles

• Joscha Vollmeyer,
• Ute Baumeister and
• Sigurd Höger

Beilstein J. Org. Chem. 2014, 10, 910–920, doi:10.3762/bjoc.10.89

• °C (2d), respectively (Figure 3, Table 1). POM investigations indicate that 1a and 1d exhibit lc phases. Above the melting point, the sample of 1a exhibits a fan shaped texture under the POM and shear tests indicate a wax-like viscosity of that phase (Figure 4a). The melt becomes isotropic when

Self-assembly of metallosupramolecular rhombi from chiral concave 9,9’-spirobifluorene-derived bis(pyridine) ligands

• Rainer Hovorka,
• Sophie Hytteballe,
• Torsten Piehler,
• Georg Meyer-Eppler,
• Filip Topić,
• Kari Rissanen,
• Marianne Engeser and
• Arne Lützen

Beilstein J. Org. Chem. 2014, 10, 432–441, doi:10.3762/bjoc.10.40

• relative sizes or ratios of sizes from the DOSY experiments because the spectra were recorded in a 3:1 mixture of dichloromethane and acetonitrile of unknown viscosity which does not allowed us to calculate hydrodynamic radii.) Therefore, these NMR-spectroscopic results nicely complement the results from

Continuous flow nitration in miniaturized devices

• Amol A. Kulkarni

Beilstein J. Org. Chem. 2014, 10, 405–424, doi:10.3762/bjoc.10.38

Concise, stereodivergent and highly stereoselective synthesis of cis- and trans-2-substituted 3-hydroxypiperidines – development of a phosphite-driven cyclodehydration

• Peter H. Huy,
• Julia C. Westphal and
• Ari M. P. Koskinen

Beilstein J. Org. Chem. 2014, 10, 369–383, doi:10.3762/bjoc.10.35

• magnetically stirring, as the viscosity of the reaction mixture increases through ammonium salt precipitation during the preceding reaction. Noteworthy, Et3N is as cheap as common solvents such as THF and CH2Cl2. Furthermore, in THF the yield of 11a decreased to 58% (Table 2, entry 8), whereas in MeCN low

Cyclic phosphonium ionic liquids

• Sharon I. Lall-Ramnarine,
• Joshua A. Mukhlall,
• James F. Wishart,
• Robert R. Engel,
• Alicia R. Romeo,
• Masao Gohdo,
• Sharon Ramati,
• Marc Berman and
• Sophia N. Suarez

Beilstein J. Org. Chem. 2014, 10, 271–275, doi:10.3762/bjoc.10.22

• synthesize ILs with improved properties (such as viscosity, thermal stability, melting point, etc.) to expand their applications into larger scale processes in diverse areas. Along that vein, phosphonium ILs have been observed to have favorable characteristics, including lower costs [2][3][4][5][6], lower

• viscosity (by ~50%) [7][8][9][10][11], greater thermal stability (by ~100 °C) [10][11][12], and wider electrochemical windows compared to their ammonium congeners. The family of ILs bearing cyclic cations (pyrrolidinium, piperidinium, and azepanium) [13][14] have been shown to have better transport and

• thermal properties of the phosphonium ILs 5a–d and their ammonium congeners are given in Table 1. Comparison of the five-membered cyclic cation ILs C4mPphol NTf2 5a and C4mPyrr NTf2 (butylmethylpyrrolidinium NTf2) reveals that the viscosity of the phosphonium salt is one third higher than that of the

N,N'-(Hexane-1,6-diyl)bis(4-methyl-N-(oxiran-2-ylmethyl)benzenesulfonamide): Synthesis via cyclodextrin mediated N-alkylation in aqueous solution and further Prilezhaev epoxidation

• Julian Fischer,
• Simon Millan and
• Helmut Ritter

Beilstein J. Org. Chem. 2013, 9, 2834–2840, doi:10.3762/bjoc.9.318

• expected [26][27][28]. As illustrated in Figure 2A, oscillatory measurements display an initial high viscosity for a mixture of 6 and 8, since its complex viscosity (η*), calculated from storage modulus G’ and loss modulus G’’, exhibits low four-digit values at 50 °C. However, η* increases further on time

• protons. Oscillatory rheological measurements of an equimolar mixture of 6 and 8 at 50 °C. Illustrated is the complex viscosity (A), as well as G’ and G’’ (B) in dependence of time. The polymer 9 is displayed as an idealized structure (R = H or polymer network; crosslinking via addition of epoxide

Oligomeric epoxide–amine adducts based on 2-amino-N-isopropylacetamide and α-amino-ε-caprolactam: Solubility in presence of cyclodextrin and curing properties

• Julian Fischer and
• Helmut Ritter

Beilstein J. Org. Chem. 2013, 9, 2803–2811, doi:10.3762/bjoc.9.315

• mixtures were analyzed by oscillatory rheology and differential scanning calorimetry, whereby significant differences in setting time, viscosity, and stiffness were observed. Keywords: amino acids; curing properties; cyclodextrin; epoxide–amine oligomers; LCST; Introduction Many partially hydrophobic

• were evaluated by applying oscillatory rheological measurements. A mixture of 5 and 8 showed a low viscosity before hardening. As illustrated in Figure 4a, the mixture exhibits one-digit values for storage modulus G’ and loss modulus G’’ at first. With continuous reaction time the curves for G‘ and G

• the complex viscosity (η*) calculated from G‘ and G‘‘. As expected, the curves confirm the above described observations. In addition, η* at gel point transition of 10 compared to that of 9 is higher by factor of 2.8 (η* = 74 kPa*s (10), η* = 26 kPa*s (9)). The difference in rigidity of the cured

Flow synthesis of phenylserine using threonine aldolase immobilized on Eupergit support

• Jagdish D. Tibhe,
• Hui Fu,
• Timothy Noël,
• Qi Wang,
• Jan Meuldijk and
• Volker Hessel

Beilstein J. Org. Chem. 2013, 9, 2168–2179, doi:10.3762/bjoc.9.254

• calculate the mass transfer coefficient, porosity (ε) = 0.5 estimated, density (ρ) = 1024 kg/m3, viscosity of fluid (μ) = 0.00134 kg/ms and thermal conductivity (K) = 0.58 (W/m·K). The Reynolds number (Re) for a fluid flow through a bed of approximately spherical particles of diameter D can be calculated

Linkage of α-cyclodextrin-terminated poly(dimethylsiloxanes) by inclusion of quasi bifunctional ferrocene

• Helmut Ritter,
• Berit Knudsen and
• Valerij Durnev

Beilstein J. Org. Chem. 2013, 9, 1278–1284, doi:10.3762/bjoc.9.144

• . Certainly, the viscosity of the poly(dimethylsiloxane) educts and the complexed systems is of great interest. However, a significant increase of the viscosity in solution could not be detected under the applied conditions, probably due to the relatively high shear forces, which cause the decomplexation of

• significantly shifts from 343 nm to 615 and 5489 nm. The hydrodynamic diameter of 615 nm can be explained by the formation of some macrocycles and oligomers by noncovalent interactions of the host and guest molecules. This phenomenon might also explain the almost unchanged viscosity increase of the complex in

• relatively poor with respect to shear forces during viscosity measurements. Experimental Materials and methods Commercial reagents and solvents were purchased from ABCR and Sigma Aldrich and used as received. When necessary, solvents were dried and purified by appropriate standard procedures. Mono-(6-(p

C–C Bond formation catalyzed by natural gelatin and collagen proteins

• Dennis Kühbeck,
• Basab Bijayi Dhar,
• Eva-Maria Schön,
• Carlos Cativiela,
• Vicente Gotor-Fernández and
• David Díaz Díaz

Beilstein J. Org. Chem. 2013, 9, 1111–1118, doi:10.3762/bjoc.9.123

• ; Lot No. 051M0012V; CAS 9000-70-8; Type B, derived from lime-cured tissue; ~225 Bloom; 73% protein content by Biuret) and gelatin from cold water fish skin (Cat. No. G7041-100G; Lot No. 071M0258V; CAS 9000-70-8; ash content 0.3%; heavy metals content 1 ppm; viscosity 8.9 CS, 10% solution, 30 °C) were

Synthesis of guanidinium–sulfonimide ion pairs: towards novel ionic liquid crystals

• Martin Butschies,
• Manuel M. Neidhardt,
• Markus Mansueto,
• Sabine Laschat and
• Stefan Tussetschläger

Beilstein J. Org. Chem. 2013, 9, 1093–1101, doi:10.3762/bjoc.9.121

• Seddon and Bruce [13]. Regarding ionic liquids, sulfonimides have been used in various ways. Particularly interesting is the symmetrical bistriflimide anion [14], which leads to desirable properties such as hydrolytic stability, low viscosity or low melting points in the ionic liquids [1][4][15][16][17

Camera-enabled techniques for organic synthesis

• Steven V. Ley,
• Richard J. Ingham,
• Matthew O’Brien and
• Duncan L. Browne

Beilstein J. Org. Chem. 2013, 9, 1051–1072, doi:10.3762/bjoc.9.118

• chemistry experimentation where one may wish to record colour changes, crystallisation, precipitation, viscosity and other phase changes, or detect the onset of polymerisation and gas evolution. Indeed, there are many examples in the literature whereby this basic level of monitoring and recording can be

A new family of four-ring bent-core nematic liquid crystals with highly polar transverse and end groups

• Kalpana Upadhyaya,
• Venkatesh Gude,
• Golam Mohiuddin and
• Rao V. S. Nandiraju

Beilstein J. Org. Chem. 2013, 9, 26–35, doi:10.3762/bjoc.9.4

• range of stable bent-core mesogens exhibiting a wide spectrum of physical properties, further experimental studies, i.e., examining birefringence, elastic constants, viscosity, and electro-optical characteristics, are in progress in fundamental and applied research. Attempts to realize the enantiotropic

Influence of cyclodextrin on the solubility and the polymerization of (meth)acrylated Triton^® X-100

• Melanie Kemnitz and
• Helmut Ritter

Beilstein J. Org. Chem. 2012, 8, 2176–2183, doi:10.3762/bjoc.8.245

• , matrix-assisted laser desorption ionization mass spectrometry (MALDI-TOF MS), dynamic light scattering (DLS), gel-permeation chromatography (GPC) and turbidity measurements. Additionally, the viscosity change of the methacrylic homopolymer with RAMEB-CD was evaluated. Keywords: (meth)acrylated Triton

• -complex was monitored by viscosity measurements. Results and Discussion Complexation study of Triton® X-100 with RAMEB-CD The complexation behavior of Triton® X-100 (1) with RAMEB-CD was investigated by means of an ITC experiment (Supporting Information File 1, Figure S1). Assuming the sequential-binding

• behavior of the RAMEB-CD-double-complexed methacrylic homopolymer (8) The rheological experiments were performed in a temperature range of 25 to 85 °C for constant shear rates. Below 30 °C the viscosity of an aqueous polymer solution decreases with increasing temperature (Figure 3, I). Surprisingly, above

Flow photochemistry: Old light through new windows

• Jonathan P. Knowles,
• Luke D. Elliott and
• Kevin I. Booker-Milburn

Beilstein J. Org. Chem. 2012, 8, 2025–2052, doi:10.3762/bjoc.8.229

Influence of intramolecular hydrogen bonds on the binding potential of methylated β-cyclodextrin derivatives

• Gerhard Wenz

Beilstein J. Org. Chem. 2012, 8, 1890–1895, doi:10.3762/bjoc.8.218

• already applied industrially on a large scale, e.g., for switching the viscosity of polymeric thickeners [22], for decontamination of soil [23][24], or for cosmetic formulations [25]. High binding potentials of the methylated CDs are essential for their specific functions in these applications. Therefore

Polysiloxane ionic liquids as good solvents for β-cyclodextrin-polydimethylsiloxane polyrotaxane structures

• Narcisa Marangoci,
• Rodinel Ardeleanu,
• Laura Ursu,
• Constanta Ibanescu,
• Maricel Danu,
• Mariana Pinteala and
• Bogdan C. Simionescu

Beilstein J. Org. Chem. 2012, 8, 1610–1618, doi:10.3762/bjoc.8.184

• wt % PRot with PDMS-Im/Br turned into a viscous clear solution, suggesting a complete dissolution. Cooling the sample to room temperature in a dry box caused an increase in the apparent viscosity; it should also be mentioned that the mixture remained clear for the next five weeks (Figure 1). This

• increased. Rotational measurements were also carried out for a better understanding of the rheological behavior of the analyzed samples. The flow curves were recorded both in terms of the shear stress (τ) and viscosity (η) (Figure 6). The ionic liquid exhibits Newtonian behavior for almost the entire

• measurement domain, with a viscosity that is independent of the shear rate. A deviation from linearity appears only for high shear rates. An important increase, both in terms of viscosity and shear stress, is noticed when rotaxane is added to the ionic liquid. The first Newtonian domain is obvious as well as

Supramolecular hydrogels formed from poly(viologen) cross-linked with cyclodextrin dimers and their physical properties

• Yoshinori Takashima,
• Yang Yuting,
• Miyuki Otsubo,
• Hiroyasu Yamaguchi and
• Akira Harada

Beilstein J. Org. Chem. 2012, 8, 1594–1600, doi:10.3762/bjoc.8.182

• . Hydrogelation between the CD dimer and viologen polymer Mixing the α,α-CD dimer and VP in aqueous solutions at room temperature slightly increases the viscosity of the α,α-CD dimer/VP, but hydrogels are not formed. On the other hand, after heating at 100 °C for 7 h, an aqueous solution of the α,α-CD dimer/VP

Synthesis of conformationally restricted glutamate and glutamine derivatives from carbonylation of orthopalladated phenylglycine derivatives

• Esteban P. Urriolabeitia,
• Eduardo Laga and
• Carlos Cativiela

Beilstein J. Org. Chem. 2012, 8, 1569–1575, doi:10.3762/bjoc.8.179

• ) usually comes from the reaction solvent (an alcohol). This fact guarantees the full displacement of the reaction, but sometimes hampers the purification of the target products, mainly when alcohols of high boiling point and/or viscosity are involved. However, in our method, CH2Cl2 is used as the solvent