Search results for "Reactivity"

Thiol-Stabilized Atomically Precise, Superatomic Silver Nanoparticles for Catalyzing Cycloisomerization of Alkynyl Amines

2018

Abstract Both the electronic and surface structures of metal nanomaterials play critical roles in determining their chemical properties. However, the non-molecular nature of conventional nanoparticles makes it extremely challenging to understand the molecular mechanism behind many of their unique electronic and surface properties. In this work, we report the synthesis, molecular and electronic structures of an atomically precise nanoparticle, [Ag206L72]q (L = thiolate, halide; q = charge). With a four-shell Ag7@Ag32@Ag77@Ag90 Ino-decahedral structure having a nearly perfect D5h symmetry, the metal core of the nanoparticle is co-stabilized by 68 thiolate and 4 halide ligands. Both electroche…

Structural Motifs of Alkali Metal Superbases in Non‐coordinating Solvents

2020

Abstract Lochmann–Schlosser superbases (LSB) are a standard reagent in synthetic chemistry to achieve an exchange of a proton on an organic framework with an alkali metal cation, which in turn can be replaced by a wide range of electrophilic groups. In standard examples, the deprotonating reagent consists of an equimolar mixture of n‐butyllithium and potassium t‐butoxide. However, the nature of the reactive species could not be pinned down either for this composition or for similar mixtures with comparable high reactivity. Despite the poor solubility and the fierce reactivity, some insights into this mixture were achieved by some indirect results, comparison with chemically related systems,…

Reaction of polyamines with diethyloxalate: a convenient route for the synthesis of tetraazacycloalkanes

2006

International audience; The reactivity of various polyamines with diethyloxalate has been investigated. It appears that, in similar experimental conditions, primary diamines give predominantly [2+2] adducts while the use of secondary benzylated polyamines results in [1+1] condensation. Although the intermediate tetraamides formed in the first case are extremely poorly soluble and show very slow reactivity towards reducing agents, cyclam has been obtained by using ultrasounds during the reaction of the corresponding tetraoxomacrocycle with BH 3 /THF. The [1+1] cyclization reaction of diversely N-benzylated linear tetraamines, whose selective syntheses have been devised herein, gives access t…

Systematic conformational search analysis of the SRR and RRR epimers of 7-hydroxymatairesinol

2010

An extensive and systematic conformational search was performed on the two epimers of the natural lignan 7-hydroxymatairesinol (HMR), by means of a home-made Systematic Conformational Search Analysis (SCSA) code, designed to select more and more stable conformers through sequential geometry optimization of trial structures at increasing levels of calculation theory. In the present case, the starting molecular structures were selected by the semi-empirical AM1 method and filtered – i.e. decreased in number by choosing the more stable species – on the basis of their energy calculated by the HF method and the 6-31G(d) basis set. The geometries obtained were further refined by performing densit…

Force Distribution Analysis of Mechanochemically Reactive Dimethylcyclobutene

2013

Internal molecular forces can guide chemical reactions, yet are not straightforwardly accessible within a quantum mechanical description of the reacting molecules. Here, we present a force-matching force distribution analysis (FM-FDA) to analyze internal forces in molecules. We simulated the ring opening of trans-3,4-dimethylcyclobutene (tDCB) with on-the-fly semiempirical molecular dynamics. The self-consistent density functional tight binding (SCC-DFTB) method accurately described the force-dependent ring-opening kinetics of tDCB, showing quantitative agreement with both experimental and computational data at higher levels. Mechanical force was applied in two different ways, namely, exter…

Task-Specific Organic Salts and Ionic Liquids Binary Mixtures: A Combination to Obtain 5-Hydroxymethylfurfural From Carbohydrates

2019

The increase in energy demand and depletion of fossil fuels are among major issues of modern society. Valorization and transformation of raw materials in products of industrial value represents a challenge. This justifies the growing interest of scientific research towards the identification of suitable media and methodologies able to pursue above goals, paying attention to matter of sustainability. On this subject, we studied sulfonic-acid functionalized diimidazolium salts as catalysts for the conversion of fructose and sucrose to 5-hydroxymethylfurfural (5-HMF) in an ionic liquid mixture. In general, using these salts allowed us to obtain 5-HMF in good yields from both substrates in mild…

Chemosensory reactivity and food neophobia in preschool children: impact of smell, but not of taste

2014

Context and objective: Recent studies suggested that sensory sensitivity could be linked to food neophobia, described as the reluctance to eat, or the avoidance of, new foods. The objective of the present study was twofold. Firstly, this study aimed at assessing the links between smell reactivity and taste reactivity in children. Secondly, this study assessed the links between children’s smell/taste reactivity and food neophobia. The hypothesis was that the higher the chemosensory reactivity of the child, the more the child is neophobic. Method: One hundred and three dyads of mother-child, from the Opaline cohort, were involved. The child’s food neophobia was assessed using a validated pare…

Smell but not taste reactivity is related to food neophobia in toddlers: results from the Opaline cohort

2014

National audience; Context and objective: Research has previously identified relationships between chemosensory reactivity and food neophobia in toddlers. However, most studies have addressed this question using declarative data, and without analyzing separately smell and taste. The objective of the present study was twofold. The first objective was to assess the relationships between olfactory reactivity and taste reactivity in toddlers, using experimental designs with different tastants and odorants. The second objective was to determine the relationships between olfactory /taste reactivity and food neophobia in toddlers. The hypothesis was that the higher the chemosensory reactivity of t…

A survey of tubercolin reactivity in school children and Palermo University medícal school students

1995

ETHANOL DRINKING PATTERN DIFFERENTLY AFFECTS NOVELTY-RELATED BEHAVIOUR DURING ABSTINENCE IN FEMALE RATS

2014

Withdrawal from chronic ethanol leads to a multifaceted syndrome, characterized by negative affective state. Novelty seeking and motivation, closely related to affective state, can be assessed in rodents exploring behavioural response to novelty. This study aims at assessing novelty-related behaviour in female rats during ethanol withdrawal following different self-administration patterns. Female rats underwent 9-week-, 2-bottle choice-, continuous or intermittent (3 days/week) access to 20% ethanol; they were named CARs and IARs respectively. After 12h from last ethanol access, they were tested for locomotor activity induced by a novel environment; time spent in the central area of an open…