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1890 In Science
The year 1890 in science and technology involved some significant events, listed below. Biology * September 25 – Sequoia National Park created in the United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 .... * October 1 – Yosemite National Park created in the United States. * Walter Heape successfully breeds rabbits from fertilised ovum, ova transferred from the biological mother to the uterus of an animal of a different breed. * Francis Galton announces a statistical demonstration of the uniqueness and classifiability of individual human fingerprints. * Jacques Loeb publishes his first major work on tropism, ''Der Heliotropismus der Thiere und seine Uebereinstimmung mit dem Heliotropismus der Pflanzen''. * Henry Luke Bolley at the new North Dakota State University, N ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nikolai Menshutkin
Nikolai Aleksandrovich Menshutkin (; – ) was a Russian chemist who discovered the process of converting a tertiary amine to a quaternary ammonium salt via the reaction with an alkyl halide, now known as the Menshutkin reaction. Biography Menshutkin was born in a merchant family as the sixth son of Alexander Nikolaevitch Menshutkin. He graduated with honors from gymnasium in December 1857, but only by autumn 1858 managed to enroll to the Saint Petersburg State University, as he was still under the prescribed age of 16. He studied at the faculty of physics and mathematics and was nearly expelled in the autumn of 1861 due to some political disturbances. Nevertheless, by the spring of 1862 he attained the master's degree. During the last years he became interested in chemistry, which he studied under Dmitri Mendeleev. While he acquired a sufficient knowledge of theory he was lacking practice, as at that time the entire laboratory of the university consisted of only two small rooms. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Glucose
Glucose is a sugar with the Chemical formula#Molecular formula, molecular formula , which is often abbreviated as Glc. It is overall the most abundant monosaccharide, a subcategory of carbohydrates. It is mainly made by plants and most algae during photosynthesis from water and carbon dioxide, using energy from sunlight. It is used by plants to make cellulose, the most abundant carbohydrate in the world, for use in cell walls, and by all living Organism, organisms to make adenosine triphosphate (ATP), which is used by the cell as energy. In energy metabolism, glucose is the most important source of energy in all organisms. Glucose for metabolism is stored as a polymer, in plants mainly as amylose and amylopectin, and in animals as glycogen. Glucose circulates in the blood of animals as blood sugar. The naturally occurring form is -glucose, while its Stereoisomerism, stereoisomer L-glucose, -glucose is produced synthetically in comparatively small amounts and is less biologicall ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mannonic
Mannose is a sugar with the formula , which sometimes is abbreviated Man. It is one of the monomers of the aldohexose series of carbohydrates. It is a C-2 epimer of glucose. Mannose is important in human metabolism, especially in the glycosylation of certain proteins. Several Congenital disorder of glycosylation, congenital disorders of glycosylation are associated with mutations in enzymes involved in mannose metabolism. Mannose is not an essential nutrient; it can be produced in the human body from glucose, or converted into glucose. Mannose provides 2–5 kcal/g. It is partially excreted in the urine. Etymology The root of both "mannose" and "mannitol" is manna, which the Bible describes as the food supplied to the Israelites during their journey in the region of Sinai Peninsula, Sinai. Several trees and shrubs can produce a substance called manna, such as the "manna tree" (''Fraxinus ornus'') from whose secretions mannitol was originally isolated. Structure Mannose comm ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gluconic Acid
Gluconic acid is an organic compound with molecular formula C6H12O7 and condensed structural formula HOCH2(CHOH)4CO2H. A white solid, it forms the gluconate anion in neutral aqueous solution. The salts of gluconic acid are known as "gluconates". Gluconic acid, gluconate salts, and gluconate esters occur widely in nature because such species arise from the oxidation of glucose. Some drugs are injected in the form of gluconates. Chemical structure The chemical structure of gluconic acid consists of a six-carbon chain, with five hydroxyl groups positioned in the same way as in the open-chained form of glucose, terminating in a carboxylic acid group. It is one of the 16 stereoisomers of 2,3,4,5,6-pentahydroxyhexanoic acid. Production Gluconic acid is typically produced by the aerobic oxidation of glucose in the presence of the enzyme glucose oxidase. The conversion produces gluconolactone and hydrogen peroxide. The lactone spontaneously hydrolyzes to gluconic acid in water. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Epimer
In stereochemistry, an epimer is one of a pair of diastereomers. The two epimers have opposite configuration at only one stereogenic center out of at least two. All other stereogenic centers in the molecules are the same in each. Epimerization is the interconversion of one epimer to the other epimer. Doxorubicin and epirubicin are two epimers that are used as drugs. Examples The stereoisomers β-D- glucopyranose and β-D- mannopyranose are epimers because they differ only in the stereochemistry at the C-2 position. The hydroxy group in β-D-glucopyranose is equatorial (in the "plane" of the ring), while in β-D-mannopyranose the C-2 hydroxy group is axial (up from the "plane" of the ring). These two molecules are epimers but, because they are not mirror images of each other, are not enantiomers. (Enantiomers have the same name, but differ in D and L classification.) They are also not sugar anomers, since it is not the anomeric carbon involved in the stereochemistry. Simila ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sugar
Sugar is the generic name for sweet-tasting, soluble carbohydrates, many of which are used in food. Simple sugars, also called monosaccharides, include glucose Glucose is a sugar with the Chemical formula#Molecular formula, molecular formula , which is often abbreviated as Glc. It is overall the most abundant monosaccharide, a subcategory of carbohydrates. It is mainly made by plants and most algae d ..., fructose, and galactose. Compound sugars, also called disaccharides or double sugars, are molecules made of two bonded monosaccharides; common examples are sucrose (glucose + fructose), lactose (glucose + galactose), and maltose (two molecules of glucose). White sugar is almost pure sucrose. In the body, compound sugars are hydrolysed into simple sugars. Longer chains of monosaccharides (>2) are not regarded as sugars and are called oligosaccharides or polysaccharides. Starch is a glucose polymer found in plants, the most abundant source of energy in human foo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Isomer
In chemistry, isomers are molecules or polyatomic ions with identical molecular formula – that is, the same number of atoms of each element (chemistry), element – but distinct arrangements of atoms in space. ''Isomerism'' refers to the existence or possibility of isomers. Isomers do not necessarily share similar chemical property, chemical or physical property, physical properties. Two main forms of isomerism are structural isomerism, structural (or constitutional) isomerism, in which ''chemical bond, bonds'' between the atoms differ; and stereoisomerism (or spatial isomerism), in which the bonds are the same but the ''relative positions'' of the atoms differ. Isomeric relationships form a hierarchy. Two chemicals might be the same constitutional isomer, but upon deeper analysis be stereoisomers of each other. Two molecules that are the same stereoisomer as each other might be in different conformational forms or be different Isotopologue, isotopologues. The depth of analy ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stereochemistry
Stereochemistry, a subdiscipline of chemistry, studies the spatial arrangement of atoms that form the structure of molecules and their manipulation. The study of stereochemistry focuses on the relationships between stereoisomers, which are defined as having the same molecular formula and sequence of bonded atoms (constitution) but differing in the geometric positioning of the atoms in space. For this reason, it is also known as Three-dimensional space, 3D chemistry—the prefix "stereo-" means "three-dimensionality". Stereochemistry applies to all kinds of compounds and ions, Organic chemistry, organic and Inorganic chemistry, inorganic species alike. Stereochemistry affects Biochemistry, biological, Physical chemistry, physical, and supramolecular chemistry. Stereochemistry reactivity (chemistry), reactivity of the molecules in question (dynamic stereochemistry). History In 1815, Jean-Baptiste Biot's observation of optical activity marked the beginning of organic stereochemistr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Emil Fischer
Hermann Emil Louis Fischer (; 9 October 1852 – 15 July 1919) was a German chemist and List of Nobel laureates in Chemistry, 1902 recipient of the Nobel Prize in Chemistry. He discovered the Fischer esterification. He also developed the Fischer projection, a symbolic way of drawing asymmetric carbon atoms. He also hypothesized lock and key mechanism of enzyme action. He never used his first given name, and was known throughout his life simply as Emil Fischer. Early years and career Fischer was born in Euskirchen, near Cologne, the son of Laurenz Fischer, a businessman, and his wife Julie Poensgen. After graduating he wished to study natural sciences, but his father compelled him to work in the family business until determining that his son was unsuitable. Fischer then attended the University of Bonn in 1871, but switched to the University of Strasbourg in 1872. He earned his doctorate in 1874 under Adolf von Baeyer with his study of phthaleins. Fischer remained with Baeyer i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Zeitschrift Für Physikalische Chemie
A magazine is a periodical literature, periodical publication, print or digital, produced on a regular schedule, that contains any of a variety of subject-oriented textual and visual content (media), content forms. Magazines are generally financed by advertising, newsagent's shop, purchase price, prepaid subscription business model, subscriptions, or by a combination of the three. They are categorised by their frequency of publication (i.e., as weeklies, monthlies, quarterlies, etc.), their target audiences (e.g., women's and trade magazines), their subjects of focus (e.g., popular science and religious), and their tones or approach (e.g., works of satire or humor). Appearance on the cover of print magazines has historically been understood to convey a place of honor or distinction to an individual or event. Term origin and definition Origin The etymology of the word "magazine" suggests derivation from the Arabic language, Arabic (), the broken plural of () meaning "depot, s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Menshutkin Reaction
In organic chemistry, the Menshutkin reaction converts a tertiary amine into a quaternary ammonium salt by reaction with an alkyl halide. Similar reactions occur when tertiary phosphines are treated with alkyl halides. The reaction is the method of choice for the preparation of quaternary ammonium salts. Some phase transfer catalysts (PTC) can be prepared according to the Menshutkin reaction, for instance the synthesis of triethyl benzyl ammonium chloride (TEBA) from triethylamine and benzyl chloride: Scope Reactions are typically conducted in polar solvents such as alcohols. Alkyl iodides are superior alkylating agents Alkylation is a chemical reaction that entails transfer of an alkyl group. The alkyl group may be transferred as an alkyl carbocation, a free radical, a carbanion, or a carbene (or their equivalents). Alkylating agents are reagents for effectin ... relative to the bromides, which in turn are superior to chlorides. As is typical for an SN2 proces ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
