The use of isoxazoline and isoxazole scaffolding in the design of novel thiourea and amide liquid-crystalline compounds

• Itamar L. Gonçalves,
• Rafaela R. da Rosa,
• Vera L. Eifler-Lima and
• Aloir A. Merlo

Beilstein J. Org. Chem. 2020, 16, 175–184, doi:10.3762/bjoc.16.20

• properties Mesomorphic properties of thioureas 17a–c, and 18a–c and amides 19–22 and 24 were investigated by POM and DSC. The DSC results for all compounds are summarized in Table 1. Transition temperatures, as well as the enthalpy and entropy values of each compound were acquired by differential scanning

• temperatures (°C), enthalpy/entropy for thioureas 17a–c, 18a–c and amides 19–22 and 24 upon heating.a Supporting Information Supporting Information File 255: Experimental descriptions for the preparation of compounds and characterization data. Supporting Information File 256: Differential scanning calorimetry

Effect of ring size on photoisomerization properties of stiff stilbene macrocycles

• Sandra Olsson,
• Óscar Benito Pérez,
• Magnus Blom and
• Adolf Gogoll

Beilstein J. Org. Chem. 2019, 15, 2408–2418, doi:10.3762/bjoc.15.233

• conformations. This will add an entropy penalty for the E-isomers. Interatomic distances from NOE buildup rates Interatomic distances, derived from NOE buildup rates, are summarized in Figure 7. Signal overlap prevented an analysis accounting for the presence of an ensemble of conformers such as NAMFIS [39][40

Halide metathesis in overdrive: mechanochemical synthesis of a heterometallic group 1 allyl complex

• Ross F. Koby,
• Nicholas R. Rightmire,
• Nathan D. Schley,
• Timothy P. Hanusa and
• William W. Brennessel

Beilstein J. Org. Chem. 2019, 15, 1856–1863, doi:10.3762/bjoc.15.181

• ]∞, enable an otherwise unfavorable halide metathesis to proceed with mechanochemical assistance. From this result, we demonstrate that ball milling and unexpected solid-state effects can permit seemingly unfavored reactions to occur. Keywords: caesium; entropy; intermolecular forces; mechanochemistry

• additional entropy provided by the two metal ions and the site disorder in the solid. Using a standard formula for the entropy of mixing two species (configurational entropy, ∆Smix = −nR(XA ln XA + XB ln XB) [31], and with 3 atoms distributed randomly over the three crystallographically identified metal

Functional panchromatic BODIPY dyes with near-infrared absorption: design, synthesis, characterization and use in dye-sensitized solar cells

• Quentin Huaulmé,
• Cyril Aumaitre,
• Outi Vilhelmiina Kontkanen,
• David Beljonne,
• Alexandra Sutter,
• Gilles Ulrich,
• Renaud Demadrille and
• Nicolas Leclerc

Beilstein J. Org. Chem. 2019, 15, 1758–1768, doi:10.3762/bjoc.15.169

• 0.15 eV (neglecting entropy changes during the light absorption) is required to efficiently inject photo excited electrons from the LUMO of the dyes in the CB of the oxide [34]. Usually iodine-based liquid electrolytes are comprising additives such as tert-butylpyridine (tBP) which is known to shift

Host–guest interactions in nor-seco-cucurbit[10]uril: novel guest-dependent molecular recognition and stereoisomerism

• Xiaodong Zhang,
• Wei Wu,
• Zhu Tao and
• Xin-Long Ni

Beilstein J. Org. Chem. 2019, 15, 1705–1711, doi:10.3762/bjoc.15.166

• driven by both enthalpy and entropy (ΔH = −30.96 kJ·mol−1 and TΔS = 9.46 kJ·mol−1). Evidently, the high enthalpy gain for host-1 with G1 and G2, host-2 with G1 may be attributed to the strong ion–dipole interactions between the guest and host. However, the host–guest interactions in the case of complexes

The activity of indenylidene derivatives in olefin metathesis catalysts

• Maria Voccia,
• Steven P. Nolan,
• Luigi Cavallo and
• Albert Poater

Beilstein J. Org. Chem. 2018, 14, 2956–2963, doi:10.3762/bjoc.14.275

• , apart from calculating the unscaled zero-point energies (ZPEs) and the thermal corrections and entropy effects at 298 K, and all values at a pressure of 1354 atm using the approach of Martin and co-workers [61], excluding the potential overestimation of the entropy contribution [38][62][63]. Energies

• include energies obtained at the M06/TZVPsdd level of theory corrected with zero-point energies, thermal corrections, and entropy effects evaluated at 298 K, achieved at the BP86/SVPsdd level. This computational approach for olefin metathesis with Ru based catalysts turned out to display errors of less

The influence of the cationic carbenes on the initiation kinetics of ruthenium-based metathesis catalysts; a DFT study

• Magdalena Jawiczuk,
• Angelika Janaszkiewicz and
• Bartosz Trzaskowski

Beilstein J. Org. Chem. 2018, 14, 2872–2880, doi:10.3762/bjoc.14.266

• -point LACV3P++** calculations), solvation energy, zero-point energy correction, thermal correction to enthalpy, and the negative product of temperature and entropy (at 298 K). All final estimates of Gibbs free energies include the counterpoise correction [69]. To further validate our results we used the

Dynamic light scattering studies of the effects of salts on the diffusivity of cationic and anionic cavitands

• Anthony Wishard and
• Bruce C. Gibb

Beilstein J. Org. Chem. 2018, 14, 2212–2219, doi:10.3762/bjoc.14.195

• therefore LiI should be the greatest aggregator of 2. As Table 1 reveals, this is not the case; it is NaI that has the strongest influence on the host. A straightforward answer for this may be that entropy is a part of the aggregation of 2, whereas the LMWA is purely enthalpically based. Additionally

A conformationally adaptive macrocycle: conformational complexity and host–guest chemistry of zorb[4]arene

• Liu-Pan Yang,
• Song-Bo Lu,
• Arto Valkonen,
• Fangfang Pan,
• Kari Rissanen and
• Wei Jiang

Beilstein J. Org. Chem. 2018, 14, 1570–1577, doi:10.3762/bjoc.14.134

• based on the information obtained from four representative crystal structures. In addition, heat capacity changes (ΔCp) and enthalpy–entropy compensation phenomena both indicate that solvent reorganization is also involved during the binding. This research further deepens our understanding on the

• [12] is crucial for minimizing the entropy cost in molecular recognition. In contrast, bioreceptors often possess flexible backbone structures and even undergo large amplitude conformational changes upon binding substrates [13][14]. This conformational adaptivity is the basis of the allosteric effects

• formation of 18+@ZB4 complex over the temperature range 283–313 K is very small (0.31 kJ mol−1), while the changes in ΔH and −TΔS are much larger (ca. 4–4.3 kJ mol−1). The changes in ΔH and −TΔS are opposite in signs and perfectly compensate each other. The enthalpy–entropy compensation phenomenon may be

[3 + 2]-Cycloaddition reaction of sydnones with alkynes

• Veronika Hladíková,
• Jiří Váňa and
• Jiří Hanusek

Beilstein J. Org. Chem. 2018, 14, 1317–1348, doi:10.3762/bjoc.14.113

• -phenylsydnone and DMAD was first studied by Huisgen and Gotthardt [54] in p-cymene at 90–110 °C. They found the cycloaddition to be overall second order and its activation entropy ΔS≠ = −130 J·mol−1·K−1 showed association character of the rate-limiting step with a relatively tight transition state. Moreover

• ≈ +0.3 to +0.4) was described [55] for reactions of 3-(4-substituted phenyl)sydnones with more reactive DMAD while the activation entropy (ΔS≠ = −106 to −121 J·mol−1·K−1) remained similar. The reaction mechanism (Scheme 5) consistent with these kinetic measurements involves rate-limiting formation of a

Crystal structure of the inclusion complex of cholesterol in β-cyclodextrin and molecular dynamics studies

• Elias Christoforides,
• Andreas Papaioannou and
• Kostas Bethanis

Beilstein J. Org. Chem. 2018, 14, 838–848, doi:10.3762/bjoc.14.69

• calculated by GB model and nonpolar contribution to the solvation free energy calculated using 'LCPO' surface areas) ΔGGB = ΔGgas + ΔGsolv as described by Miller et al. [50]. The entropy term T∙ΔS was also calculated from normal mode analysis with constant temperature using the respective module of the Amber

• 12 suite and added to the ΔGGB term according to: ΔGbind = ΔGGB − T∙ΔS. The entropy term was calculated by taking snapshots every 100 frames for as long as the equilibrated system of the inclusion complex was subjected to MD simulations. However, it should be noted that the estimation of the entropy

• term is often problematic as the normal mode lacks information of the conformational entropy and alternative methods do not give converged results [51]. Thus, this term is usually omitted and the comparison between similar complexes is based on the ΔGGB solely. Schematic representation of (a) the

Binding abilities of polyaminocyclodextrins: polarimetric investigations and biological assays

• Marco Russo,
• Daniele La Corte,
• Annalisa Pisciotta,
• Serena Riela,
• Rosa Alduina and
• Paolo Lo Meo

Beilstein J. Org. Chem. 2017, 13, 2751–2763, doi:10.3762/bjoc.13.271

• consequent unfavourable effect on the complex formation entropy [43][50]. A further unfavourable contribution may also come from the increasingly difficult desolvation of the charged host. These combined effects cause the observed decrease of K values for the neutral guest 1. By contrast, for the anionic

• that the ancillary chain of 3 is unable to give multiple hydrogen bonding with the host cavity, due to the methyl group placed on the amino N atom. According to literature, this peculiar structural feature is able to enhance largely the outcome of entropy-unfavourable stiffening effects [50][52]. On

Binding abilities of a chiral calix[4]resorcinarene: a polarimetric investigation on a complex case of study

• Marco Russo and
• Paolo Lo Meo

Beilstein J. Org. Chem. 2017, 13, 2698–2709, doi:10.3762/bjoc.13.268

• interactions, π–π interactions, desolvation effects and entropy-unfavorable conformational dynamic restraints. Polarimetry is confirmed as a very useful and versatile tool for the investigation of supramolecular interactions with chiral hosts, even in complex systems involving multiple equilibria. Keywords

What contributes to an effective mannose recognition domain?

• Christoph P. Sager,
• Deniz Eriş,
• Martin Smieško,
• Rachel Hevey and
• Beat Ernst

Beilstein J. Org. Chem. 2017, 13, 2584–2595, doi:10.3762/bjoc.13.255

• water molecule does not lead to an additional entropy penalty upon H-bonding to the ligand. As a result, the interaction benefits from an enthalpic gain without suffering from an entropic penalty [58]. Examples of such highly conserved water molecules are found in both, L-arabinose binding protein (ABP

• ). With the entropically driven sLex interaction, surface waters are displaced to the bulk and penalized by a positive enthalpy term resulting from a desolvation penalty that is not compensated by the newly formed electrostatic interactions (Figure 6) [67]. According to Dunitz [68], the entropy that can

• overall enthalpic benefit by forming additional interactions at a reduced cost. In addition, the entropy gained by releasing three water molecules into bulk, as compared to only two, should also be taken into account. The formation of multiple H-bonds in rigid, buried binding sites is an alternative way

One-pot three-component route for the synthesis of S-trifluoromethyl dithiocarbamates using Togni’s reagent

• Azim Ziyaei Halimehjani,
• Martin Dračínský and
• Petr Beier

Beilstein J. Org. Chem. 2017, 13, 2502–2508, doi:10.3762/bjoc.13.247

• ) provided the rates of rotation around the N–C bond at all temperatures and the Eyring plot (Figure 2) allowed to determine the enthalpy and entropy of activation. The entropy of activation is small (−4.2 cal/K) and the free energy of activation (15.8 kcal/mol at 300 K) is dominated by the enthalpic term

β-Cyclodextrin- and adamantyl-substituted poly(acrylate) self-assembling aqueous networks designed for controlled complexation and release of small molecules

• Liang Yan,
• Duc-Truc Pham,
• Philip Clements,
• Stephen F. Lincoln,
• Jie Wang,
• Xuhong Guo and
• Christopher J. Easton

Beilstein J. Org. Chem. 2017, 13, 1879–1892, doi:10.3762/bjoc.13.183

• adamantyl group and its dodecyl tether as is discussed below. The large K for the PAAβ-CDen/PAAADen and PAAβ-CDen/PAAADhn systems are mainly due to substantial ΔH contributions (Table 1). The negative TΔS for the PAAβ-CDen/PAAADen system is attributable to the entropy loss arising from the combination of

• the β-CDen and ADen substituents into a single complex and network formation outweighing the entropy gain [49][50] anticipated for the displacement of water from the β-CDen annulus by the ADen substituent. This offset is smaller for the PAAβ-CDen/PAAADhn system possibly because the ADhn substituent

• hexyl tether allows more network flexibility. The K for the PAAβ-CDen/PAAADddn system is the largest observed as a consequence of a smaller ΔH being offset by a positive TΔS. This probably arises from the entropy loss expected for complexation of the adamantyl group and the dodecyl tether of the ADddn

Grip on complexity in chemical reaction networks

• Albert S. Y. Wong and
• Wilhelm T. S. Huck

Beilstein J. Org. Chem. 2017, 13, 1486–1497, doi:10.3762/bjoc.13.147

• equilibrium (i.e., in a thermodynamically open system), the implementation of CRNs often suffices with the assumption of an excess of a source (S) combined with a product (P) that acts as a sink. In such dissipative conditions, reactions do not necessarily settle for the state with the highest entropy but

Towards open-ended evolution in self-replicating molecular systems

• Herman Duim and
• Sijbren Otto

Beilstein J. Org. Chem. 2017, 13, 1189–1203, doi:10.3762/bjoc.13.118

• defying the second law of thermodynamics, as the system as a whole still evolves towards increasing entropy. With replicator complexification having been made feasible, it then only depends on evolutionary possibilities and benefits whether complexification also actually occurs. In order for the

Glycoscience@Synchrotron: Synchrotron radiation applied to structural glycoscience

• Serge Pérez and
• Daniele de Sanctis

Beilstein J. Org. Chem. 2017, 13, 1145–1167, doi:10.3762/bjoc.13.114

• surface entropy and hinder crystal packing. For this reason, it is sometime necessary to manipulate the glycoform to facilitate the crystallization. In the case of the human IgE-FcεRIα [31], Man5-GlcNAc-GlcNAc-Asp-linked glycoforms produced better crystals than in the case where only the Man-GlcNAc-GlcNAc

From chemical metabolism to life: the origin of the genetic coding process

• Antoine Danchin

Beilstein J. Org. Chem. 2017, 13, 1119–1135, doi:10.3762/bjoc.13.111

• function associated to this view is that the cell separates between an inside and an outside. In 1935, James Danielli proposed with Hugh Davson that this embodiment was achieved by formation of a bilayer made of amphiphilic lipid molecules [11]. This process is entropy-driven (life belongs to physics, it

• water by an entropy increase, if a selection process retains the macromolecules in a specific compartment. Surface metabolism at the origin of life is perhaps the simplest way to harness this ubiquitous property of thermodynamics. Samuel Granick, very early on, remarked the important role of transition

• recently proposed by the same author and his colleagues [24]. However, while these syntheses may operate under relatively mild conditions with compounds from volcanic emanations, they still need to be complemented by an entropy-driven process favouring polymerisation. Alternating dry and wet episodes might

How and why kinetics, thermodynamics, and chemistry induce the logic of biological evolution

• Addy Pross and
• Robert Pascal

Beilstein J. Org. Chem. 2017, 13, 665–674, doi:10.3762/bjoc.13.66

• develops these lines of thought and argues against the validity of a thermodynamic approach in which the maximisation of the rate of energy dissipation/entropy production is considered to direct the evolutionary process. More generally, our analysis reaffirms the predominant role of kinetics in the self

• living state? (2) If so, by what mechanistic means can a chemical system self-organise to yield the living state, consistent with the constraints of the Second Law. These considerations infer that an overall spontaneous decrease in entropy is statistically highly unlikely, and for macroscopic systems

• production of entropy in the environment. The identification of such a driving force would make it possible to determine the parameters influencing change, even though no historical information regarding its early expression is available. Furthermore, identification of that driving force could serve as a

Dimerization reactions of aryl selenophen-2-yl-substituted thiocarbonyl S-methanides as diradical processes: a computational study

• Michael L. McKee,
• Grzegorz Mlostoń,
• Katarzyna Urbaniak and
• Heinz Heimgartner

Beilstein J. Org. Chem. 2017, 13, 410–416, doi:10.3762/bjoc.13.44

• with solvation effects (assuming ∆H(solv) = ∆G(solv)) to obtain enthalpies at 298 K in THF (Equation 1). The calculated entropy was used to determine the –T∆S term to form free energies at 298 K in THF (Equation 2). Structures of the reactive intermediates as a diradical 6 or a zwitterion 7 in the

Interactions between cyclodextrins and cellular components: Towards greener medical applications?

• Loïc Leclercq

Beilstein J. Org. Chem. 2016, 12, 2644–2662, doi:10.3762/bjoc.12.261

• of HP-β- and ME-β-CD is endothermic and entropy driven. As native and modified CDs are able to complex some amino acids which constitute peptides and proteins, these molecules can be useful for their separation by capillary zone electrophoresis. In this context, Rathore and Horváth reported that

Diels–Alder reactions in confined spaces: the influence of catalyst structure and the nature of active sites for the retro-Diels–Alder reaction

• Ángel Cantín,
• M. Victoria Gomez and
• Antonio de la Hoz

Beilstein J. Org. Chem. 2016, 12, 2181–2188, doi:10.3762/bjoc.12.208

• . The effect of confinement of the reactant within the pores of the catalyst can decrease the entropy of the activated complex [17][18][19][20][21][22][23][24][25][26][29][30] producing not only an increase of the reaction rate but also a modification of the selectivity. To study this effect, we have

Experimental and theoretical investigations on the high-electron donor character of pyrido-annelated N-heterocyclic carbenes

• Michael Nonnenmacher,
• Dominik M. Buck and
• Doris Kunz

Beilstein J. Org. Chem. 2016, 12, 1884–1896, doi:10.3762/bjoc.12.178

• preferred exchange of the cis-CO ligand (Scheme 2). This is in accordance with the experimental observation of the 13CO exchange. Although the formation of 3a NHC/COapic from 2a and CO is exothermic (ΔH298K,1bar = −11.4 kJ/mol), considering the entropy leads to an endergonic reaction (ΔG298K,1bar = 29.4 kJ