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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. * October 1 – Yosemite National Park created in the United States. * Walter Heape successfully breeds rabbits from fertilised 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 Agricultural College isolates the organism responsible for potato scab and develops an effective treatment. Chemistry * Nikolai Menshutkin discovers that a tertiary amine can be converted into a quaternary ammonium salt by reaction with an alkyl halide – the Menshutkin rea ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nikolai Menshutkin
Nikolai Aleksandrovich Menshutkin (russian: Николай Александрович Меншуткин; – ) 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 en ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Glucose
Glucose is a simple sugar with the molecular formula . Glucose is overall the most abundant monosaccharide, a subcategory of carbohydrates. Glucose is mainly made by plants and most algae during photosynthesis from water and carbon dioxide, using energy from sunlight, where it is used to make cellulose in cell walls, the most abundant carbohydrate in the world. 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 starch and amylopectin, and in animals as glycogen. Glucose circulates in the blood of animals as blood sugar. The naturally occurring form of glucose is -glucose, while -glucose is produced synthetically in comparatively small amounts and is less biologically active. Glucose is a monosaccharide containing six carbon atoms and an aldehyde group, and is therefore an aldohexose. The glucose molecule can exist in an open-chain (acyclic) as well as ring (cyclic) form. Gluco ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mannonic
Mannose is a sugar monomer 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 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. 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 commonly exists as two different-sized rings, the pyranose (six-membered) form and the furanose (five-membered) form. Each ring ... [...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)4COOH. It is one of the 16 stereoisomers of 2,3,4,5,6-pentahydroxyhexanoic acid. In aqueous solution at neutral pH, gluconic acid forms the gluconate ion. 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. In aqueous solution, gluconic acid exists in equilibrium with the cyclic ester glucono delta-lactone. Production Gluconic acid preparation was first reported by Hlasiwetz and Habermann in 1870 and involved the chemical oxidation of glucose. In 1880, Boutroux ... [...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, 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 a refined form of 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 food. Some other chemical substances, such as glycerol and sugar alcohols, may have a sweet taste, but are not classified as sugar. Sugars are found in the tissues of most plants. Honey and fruits are abundant natural sources of simple sugars. Suc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Isomer
In chemistry, isomers are molecules or polyatomic ions with identical molecular formulae – that is, same number of atoms of each element – but distinct arrangements of atoms in space. Isomerism is existence or possibility of isomers. Isomers do not necessarily share similar chemical or physical properties. Two main forms of isomerism are structural or constitutional isomerism, in which ''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 isotopologues. The depth of analysis depends on the field of study or the chemical and physical properties of interest. The English word "isomer" () is a back-for ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stereochemistry
Stereochemistry, a subdiscipline of chemistry, involves the study of the relative spatial arrangement of atoms that form the structure of molecules and their manipulation. The study of stereochemistry focuses on the relationships between stereoisomers, which by definition have the same molecular formula and sequence of bonded atoms (constitution), but differ in structural formula (the three-dimensional orientations of their atoms in space). For this reason, it is also known as 3D chemistry—the prefix "stereo-" means "three-dimensionality". Stereochemistry spans the entire spectrum of organic, inorganic, biological, physical and especially supramolecular chemistry. Stereochemistry includes methods for determining and describing these relationships; the effect on the physical or biological properties these relationships impart upon the molecules in question, and the manner in which these relationships influence the reactivity of the molecules in question ( dynamic stereochemis ... [...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 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, and was appointed to a position at the university. After eight ye ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Zeitschrift Für Physikalische Chemie
''Zeitschrift für Physikalische Chemie'' (English: ''Journal of Physical Chemistry'') is a monthly peer-reviewed scientific journal covering physical chemistry that is published by Oldenbourg Wissenschaftsverlag. Its English subtitle is "International Journal of Research in Physical Chemistry and Chemical Physics". It was established in 1887 by Wilhelm Ostwald, Jacobus Henricus van 't Hoff, and Svante August Arrhenius as the first scientific journal for publications specifically in the field of physical chemistry. The editor-in-chief is Klaus Rademann (Humboldt University of Berlin). Abstracting and indexing The journal is abstracted and indexed in: According to the ''Journal Citation Reports'', the journal has a 2020 impact factor The impact factor (IF) or journal impact factor (JIF) of an academic journal is a scientometric index calculated by Clarivate that reflects the yearly mean number of citations of articles published in the last two years in a given journal, a ... [...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 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 relative to the bromides, which in turn are superior to chlorides. As is typical for an SN2 process, benzylic, allylic, and α-carbonylated alkyl halides are excellent reactants. Even though alkyl chlorides are poor alkylating agents (''gem''-dichlorides especially so), amines should not be handled in chlorinated solvents such as dichloromethane and dichlo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
