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Nucleophiles
In chemistry, a nucleophile is a chemical species that forms bonds by donating an electron pair. All molecules and ions with a free pair of electrons or at least one pi bond can act as nucleophiles. Because nucleophiles donate electrons, they are Lewis bases. ''Nucleophilic'' describes the affinity of a nucleophile to bond with positively charged atomic nuclei. Nucleophilicity, sometimes referred to as nucleophile strength, refers to a substance's nucleophilic character and is often used to compare the affinity of atoms. Neutral nucleophilic reactions with solvents such as alcohols and water are named solvolysis. Nucleophiles may take part in nucleophilic substitution, whereby a nucleophile becomes attracted to a full or partial positive charge, and nucleophilic addition. Nucleophilicity is closely related to basicity. The difference between the two is, that basicity is a thermodynamic property (i.e. relates to an equilibrium state), but nucleophilicity is a kinetic property, whic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alpha Effect
The alpha effect refers to the increased Nucleophile, nucleophilicity of an atom due to the presence of an adjacent (alpha) atom with lone pair electrons. This first atom does not necessarily exhibit increased basicity compared with a similar atom without an adjacent electron-donating atom, resulting in a deviation from the classical Brønsted-type reactivity-basicity relationship. In other words, the alpha effect refers to nucleophiles presenting higher nucleophilicity than the predicted value obtained from the Brønsted basicity. The representative examples would be high nucleophilicities of hydroperoxide (HO2−) and hydrazine (N2H4). The effect is now well established with numerous examples and became an important concept in mechanistic chemistry and biochemistry. However, the origin of the effect is still controversial without a clear winner. Background Experiment The effect was first observed by Jencks and Carriuolo in 1960 in a series of chemical kinetics experiments in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nucleophilic Substitution
In chemistry, a nucleophilic substitution (SN) is a class of chemical reactions in which an electron-rich chemical species (known as a nucleophile) replaces a functional group within another electron-deficient molecule (known as the electrophile). The molecule that contains the electrophile and the leaving functional group is called the substrate. The most general form of the reaction may be given as the following: :\text\mathbf + \ce + \text\mathbf The electron pair (:) from the nucleophile (Nuc) attacks the substrate () and bonds with it. Simultaneously, the leaving group (LG) departs with an electron pair. The principal product in this case is . The nucleophile may be electrically neutral or negatively charged, whereas the substrate is typically neutral or positively charged. An example of nucleophilic substitution is the hydrolysis of an alkyl bromide, R-Br under basic conditions, where the attacking nucleophile is hydroxyl () and the leaving group is bromide (). :O ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electrophile
In chemistry, an electrophile is a chemical species that forms bonds with nucleophiles by accepting an electron pair. Because electrophiles accept electrons, they are Lewis acids. Most electrophiles are positively Electric charge, charged, have an atom that carries a partial positive charge, or have an atom that does not have an octet of electrons. Electrophiles mainly interact with nucleophiles through Addition reaction, addition and Substitution reaction, substitution reactions. Frequently seen electrophiles in Organic synthesis, organic syntheses include cations such as Hydrogen ion, H+ and nitrosonium, NO+, polarized neutral molecules such as hydrogen chloride, HCl, alkyl halides, acyl halides, and carbonyl compounds, polarizable neutral molecules such as chlorine, Cl2 and bromine, Br2, oxidizing agents such as organic peracids, chemical species that do not satisfy the octet rule such as carbenes and Radical (chemistry), radicals, and some Lewis acids such as Borane, BH3 and Di ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nucleophilic Addition
In organic chemistry, a nucleophilic addition (AN) reaction is an addition reaction where a chemical compound with an electrophilic double or triple bond reacts with a nucleophile, such that the double or triple bond is broken. Nucleophilic additions differ from electrophilic additions in that the former reactions involve the group to which atoms are added accepting electron pairs, whereas the latter reactions involve the group donating electron pairs. Addition to carbon–heteroatom double bonds Nucleophilic addition reactions of nucleophiles with electrophilic double or triple bond (π bonds) create a new carbon center with two additional single, or σ, bonds.March Jerry; (1985). Advanced Organic Chemistry reactions, mechanisms and structure (3rd ed.). New York: John Wiley & Sons, inc. Addition of a nucleophile to carbon–heteroatom double or triple bonds such as >C=O or -C≡N show great variety. These types of bonds are polar (have a large difference in electronegativit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Christopher Kelk Ingold
Sir Christopher Kelk Ingold (28 October 1893 – 8 December 1970) was a British chemist based in Leeds and London. His groundbreaking work in the 1920s and 1930s on reaction mechanisms and the electronic structure of organic compounds was responsible for the introduction into mainstream chemistry of concepts such as nucleophile, electrophile, inductive and resonance effects, and such descriptors as SN1, SN2, E1, and E2. He also was a co-author of the Cahn–Ingold–Prelog priority rules. Ingold is regarded as one of the chief pioneers of physical organic chemistry. Early life and education Born in London to a silk merchant who died of tuberculosis when Ingold was five years old, Ingold began his scientific studies at Hartley University College at Southampton (now Southampton University) taking an external BSc in 1913 with the University of London. He then joined the laboratory of Jocelyn Field Thorpe at Imperial College, London, with a brief hiatus from 1918–1920 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Solvolysis
In chemistry, solvolysis is a type of nucleophilic substitution (S1/S2) or elimination reaction, elimination where the nucleophile is a solvent molecule. Characteristic of S1 reactions, solvolysis of a chirality (chemistry), chiral reactant affords the racemate. Sometimes however, the stereochemical course is complicated by intimate ion pairs, whereby the leaving anion remains close to the carbocation, effectively shielding it from an attack by the nucleophile. Particularly fast reactions can occur by neighbour group participation, with nonclassical ions as intermediates or transition states. Examples For certain nucleophiles, solvolysis reactions are classified. Solvolysis involving water (molecule), water is called hydrolysis. Related terms are alcoholysis (Alcohol (chemistry), alcohols) and specifically methanolysis (methanol), acetolysis, ammonolysis (ammonia), and aminolysis (alkyl amines). Glycolysis is however an older term for the multistep conversion of glucose to pyruvat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
-phil-
The Greek root ''-phil-'' originates from the Greek word meaning "love". For example, philosophy (along with the Greek root ''-soph-'' meaning "wisdom") is the study of human customs and the significance of life. One of the most common uses of the root ''-phil-'' is with philias. A philia is the love or obsession with a particular thing or subject. The suffix ''-philia'' is used to specify the love or obsession with something more specific. It is somewhat antonymic to '' -phobia''. Philias can be biological (e.g. rhizophilia, preference for living on roots) or chemical (e.g. chromophilous, materials that stain easily), or can be a hobby/liking (e.g. icthyophilia, love for fish). ' () as a Greek word for love refers to brotherly love, including friendship and affection. This contrasts to the Greek terms Eros, or sexual/romantic love, and agape, or detached, spiritual love. However, English usage differs in some cases from the etymological use, and several of these words ref ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pseudo First Order Reaction
In chemistry, the rate equation (also known as the rate law or empirical differential rate equation) is an empirical differential mathematical expression for the reaction rate of a given reaction in terms of concentrations of chemical species and constant parameters (normally rate coefficients and partial orders of reaction) only. For many reactions, the initial rate is given by a power law such as :v_0\; =\; k mathrmx mathrmy where and are the molar concentrations of the species and usually in moles per liter (molarity, ). The exponents and are the partial ''orders of reaction'' for and , respectively, and the ''overall'' reaction order is the sum of the exponents. These are often positive integers, but they may also be zero, fractional, or negative. The order of reaction is a number which quantifies the degree to which the rate of a chemical reaction depends on concentrations of the reactants. In other words, the order of reaction is the exponent to which the concentrati ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alcohol (chemistry)
In chemistry, an alcohol (), is a type of organic compound that carries at least one hydroxyl () functional group bound to a Saturated and unsaturated compounds, saturated carbon atom. Alcohols range from the simple, like methanol and ethanol, to complex, like sugar alcohols and cholesterol. The presence of an OH group strongly modifies the properties of Hydrocarbon, hydrocarbons, conferring Hydrophile, hydrophilic (water-loving) properties. The OH group provides a site at which many reactions can occur. History The flammable nature of the exhalations of wine was already known to ancient natural philosophers such as Aristotle (384–322 BCE), Theophrastus (–287 BCE), and Pliny the Elder (23/24–79 CE). However, this did not immediately lead to the isolation of alcohol, even despite the development of more advanced distillation techniques in second- and third-century Roman Egypt. An important recognition, first found in one of the writings attributed to Jabir ibn Hayyan, J� ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Atomic Nucleus
The atomic nucleus is the small, dense region consisting of protons and neutrons at the center of an atom, discovered in 1911 by Ernest Rutherford at the Department_of_Physics_and_Astronomy,_University_of_Manchester , University of Manchester based on the 1909 Geiger–Marsden experiments, Geiger–Marsden gold foil experiment. After the discovery of the neutron in 1932, models for a nucleus composed of protons and neutrons were quickly developed by Dmitri Ivanenko and Werner Heisenberg. An atom is composed of a positively charged nucleus, with a cloud of negatively charged electrons surrounding it, bound together by electrostatic force. Almost all of the mass of an atom is located in the nucleus, with a very small contribution from the electron cloud. Protons and neutrons are bound together to form a nucleus by the nuclear force. The diameter of the nucleus is in the range of () for hydrogen (the diameter of a single proton) to about for uranium. These dimensions are much ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Empirical
Empirical evidence is evidence obtained through sense experience or experimental procedure. It is of central importance to the sciences and plays a role in various other fields, like epistemology and law. There is no general agreement on how the terms ''evidence'' and ''empirical'' are to be defined. Often different fields work with quite different conceptions. In epistemology, evidence is what justifies beliefs or what determines whether holding a certain belief is rational. This is only possible if the evidence is possessed by the person, which has prompted various epistemologists to conceive evidence as private mental states like experiences or other beliefs. In philosophy of science, on the other hand, evidence is understood as that which '' confirms'' or ''disconfirms'' scientific hypotheses and arbitrates between competing theories. For this role, evidence must be public and uncontroversial, like observable physical objects or events and unlike private mental states, so ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydrox Subst
Hydrox is a creme-filled chocolate sandwich cookie currently owned and manufactured by Leaf Brands. It debuted in the United States in 1908, and was manufactured by Sunshine Biscuits for over 90 years. Hydrox was largely discontinued in 1999, three years after Sunshine was acquired by Keebler Company, Keebler, which was later acquired by Kellogg's which in turn sold the cookie line and the rights to the Keebler name to Ferrero SpA. In September 2015, the product was reintroduced by Leaf Brands. Oreo was created in 1912 as an imitation of Hydrox. Oreo eventually surpassed Hydrox in popularity, which resulted in the Hydrox cookies being perceived by many as an imitation of Oreo, despite the opposite being the case. Compared to Oreos, Hydrox cookies have a less sweet filling and a crunchier cookie shell that is less soggy when dipped in milk. History In 1908, the cookie's creation was inspired by "purity and goodness", with a name derived from the hydrogen and oxygen elements wit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
