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Ascorbic Acid (molecular Aspects)
Ascorbic acid is an organic compound with formula , originally called hexuronic acid. It is a white solid, but impure samples can appear yellowish. It dissolves well in water to give mildly acidic solutions. It is a mild reducing agent. Ascorbic acid exists as two enantiomers (mirror-image isomers), commonly denoted "" (for "levo") and "" (for "dextro"). The isomer is the one most often encountered: it occurs naturally in many foods, and is one form ("vitamer") of vitamin C, an essential nutrient for humans and many animals. Deficiency of vitamin C causes scurvy, formerly a major disease of sailors in long sea voyages. It is used as a food additive and a dietary supplement for its antioxidant properties. The "" form can be made via chemical synthesis but has no significant biological role. History The antiscorbutic properties of certain foods were demonstrated in the 18th century by James Lind. In 1907, Axel Holst and Theodor Frølich discovered that the antiscorbutic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diethyl Ether
Diethyl ether, or simply ether, is an organic compound in the ether class with the formula , sometimes abbreviated as (see Pseudoelement symbols). It is a colourless, highly volatile, sweet-smelling ("ethereal odour"), extremely flammable liquid. It is commonly used as a solvent in laboratories and as a starting fluid for some engines. It was formerly used as a general anesthetic, until non-flammable drugs were developed, such as halothane. It has been used as a recreational drug to cause intoxication. Production Most diethyl ether is produced as a byproduct of the vapor-phase hydration of ethylene to make ethanol. This process uses solid-supported phosphoric acid catalysts and can be adjusted to make more ether if the need arises. Vapor-phase dehydration of ethanol over some alumina catalysts can give diethyl ether yields of up to 95%. Diethyl ether can be prepared both in laboratories and on an industrial scale by the acid ether synthesis. Ethanol is mixed with a stro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Axel Holst
Axel Holst (6 September 1860 – 26 April 1931) was a Norwegian Professor of Hygiene and Bacteriology at the University of Oslo. He was most known for his contributions to the study of the treatment of Beriberi and Scurvy. Biography Holst was born in Christiania (now Oslo), Norway. He was the son of Axel Holst (1826–80) and Anna Mathilde Charlotte Flemming (1832–97). He was the brother of the linguist Clara Holst and grandson of Frederik Holst. Both his father and grandfather were physicians. Holst attended Christiania Cathedral School (1877). He studied at Royal Frederick University (now University of Oslo) gaining his cand.med. in 1884. In 1887, he was awarded the Crown Prince's gold medal (''Kronprinsens gullmedalje''). He was granted his doctorate in 1892 involving the bacterium streptococcus. He was an assistant at the National Institute of Pathological Anatomy from 1885-89. During 1890-1892, he studied at various European laboratories including visits a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Enediol
In organic chemistry, alkenols (shortened to enols) are a type of reactive structure or intermediate in organic chemistry that is represented as an alkene (olefin) with a hydroxyl group attached to one end of the alkene double bond (). The terms ''enol'' and ''alkenol'' are portmanteaus deriving from "-ene"/"alkene" and the "-ol" suffix indicating the hydroxyl group of alcohols, dropping the terminal "-e" of the first term. Generation of enols often involves removal of a hydrogen adjacent (α-) to the carbonyl group—i.e., deprotonation, its removal as a proton, . When this proton is not returned at the end of the stepwise process, the result is an anion termed an enolate (see images at right). The enolate structures shown are schematic; a more modern representation considers the molecular orbitals that are formed and occupied by electrons in the enolate. Similarly, generation of the enol often is accompanied by "trapping" or masking of the hydroxy group as an ether, such as a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lactone
Lactones are cyclic carboxylic esters, containing a 1-oxacycloalkan-2-one structure (), or analogues having unsaturation or heteroatoms replacing one or more carbon atoms of the ring. Lactones are formed by intramolecular esterification of the corresponding hydroxycarboxylic acids, which takes place spontaneously when the ring that is formed is five- or six-membered. Lactones with three- or four-membered rings (α-lactones and β-lactones) are very reactive, making their isolation difficult. Special methods are normally required for the laboratory synthesis of small-ring lactones as well as those that contain rings larger than six-membered. Nomenclature Lactones are usually named according to the precursor acid molecule (''aceto'' = 2 carbon atoms, ''propio'' = 3, ''butyro'' = 4, ''valero'' = 5, ''capro'' = 6, etc.), with a ''-lactone'' suffix and a Greek letter prefix that specifies the number of carbon atoms in the heterocycle — that is, the distance between the relevant -OH ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Furan
Furan is a heterocyclic organic compound, consisting of a five-membered aromatic ring with four carbon atoms and one oxygen atom. Chemical compounds containing such rings are also referred to as furans. Furan is a colorless, flammable, highly volatile liquid with a boiling point close to room temperature. It is soluble in common organic solvents, including alcohol, ether, and acetone, and is slightly soluble in water. Its odor is "strong, ethereal; chloroform-like". It is toxic and may be carcinogenic in humans. Furan is used as a starting point for other speciality chemicals. History The name "furan" comes from the Latin ''furfur'', which means bran. ( Furfural is produced from bran.) The first furan derivative to be described was 2-furoic acid, by Carl Wilhelm Scheele in 1780. Another important derivative, furfural, was reported by Johann Wolfgang Döbereiner in 1831 and characterised nine years later by John Stenhouse. Furan itself was first prepared by Heinrich Lim ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tadeusz Reichstein
Tadeusz Reichstein (20 July 1897 – 1 August 1996) was a Polish-Swiss chemist and the Nobel Prize in Physiology or Medicine laureate (1950), which was awarded for his work on the isolation of cortisone. Early life Reichstein was born into a Polish-Jewish family at Włocławek, Russian Empire. His parents were Gastawa (Brockmann) and Izydor Reichstein. He spent his early childhood at Kiev, where his father was an engineer. He began his education at boarding-school in Jena, Germany and arrived in Basel, Switzerland at the age of 8. Career Reichstein studied under Hermann Staudinger during the latter's brief stint at the Technical University of Karlsruhe. It was here that he met Leopold Ruzicka, also a doctoral student. In 1933, working in Zürich, Switzerland, at the ETHZ chemical laboratories of Ruzicka, Reichstein succeeded, independently of Sir Norman Haworth and his collaborators in the United Kingdom, in synthesizing vitamin C (ascorbic acid) in what is now called the Reichs ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nobel Prize
The Nobel Prizes ( ; sv, Nobelpriset ; no, Nobelprisen ) are five separate prizes that, according to Alfred Nobel's will of 1895, are awarded to "those who, during the preceding year, have conferred the greatest benefit to humankind." Alfred Nobel was a Swedish chemist, engineer, and industrialist most famously known for the invention of dynamite. He died in 1896. In his will, he bequeathed all of his "remaining realisable assets" to be used to establish five prizes which became known as "Nobel Prizes." Nobel Prizes were first awarded in 1901. Nobel Prizes are awarded in the fields of Physics, Chemistry, Physiology or Medicine, Literature, and Peace (Nobel characterized the Peace Prize as "to the person who has done the most or best to advance fellowship among nations, the abolition or reduction of standing armies, and the establishment and promotion of peace congresses"). In 1968, Sveriges Riksbank (Sweden's central bank) funded the establishment of the Prize in Economi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
National Library Of Medicine
The United States National Library of Medicine (NLM), operated by the United States federal government, is the world's largest medical library. Located in Bethesda, Maryland, the NLM is an institute within the National Institutes of Health. Its collections include more than seven million books, journals, technical reports, manuscripts, microfilms, photographs, and images on medicine and related sciences, including some of the world's oldest and rarest works. The current director of the NLM is Patricia Flatley Brennan.National Library of Medicine Welcomes New Director Dr. Patricia Flatley Brennan . ''National Library of Medicine''. August 15, 2016. History The precursor o ...[...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paprika
Paprika ( US , ; UK , ) is a spice made from dried and ground red peppers. It is traditionally made from ''Capsicum annuum'' varietals in the Longum group, which also includes chili peppers, but the peppers used for paprika tend to be milder and have thinner flesh. In some languages, but not English, the word ''paprika'' also refers to the plant and the fruit from which the spice is made, as well as to peppers in the Grossum group (e.g. bell peppers). All capsicum varieties are descended from wild ancestors in North America, in particular Central Mexico, where they have been cultivated for centuries. The peppers were subsequently introduced to the Old World, when peppers were brought to Spain in the 16th century. The seasoning is used to add color and flavor to many types of dishes in diverse cuisines. The trade in paprika expanded from the Iberian Peninsula to Africa and Asia and ultimately reached Central Europe through the Balkans, which was then under Ottoman rule. This he ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Norman Haworth
Sir Walter Norman Haworth FRS (19 March 1883 – 19 March 1950) was a British chemist best known for his groundbreaking work on ascorbic acid (vitamin C) while working at the University of Birmingham. He received the 1937 Nobel Prize in Chemistry "for his investigations on carbohydrates and vitamin C". The prize was shared with Swiss chemist Paul Karrer for his work on other vitamins. Haworth worked out the correct structure of a number of sugars, and is known among organic chemists for his development of the Haworth projection that translates three-dimensional sugar structures into convenient two-dimensional graphical form. Academic career Having worked for some time from the age of fourteen in the local Ryland's linoleum factory managed by his father, he studied for and successfully passed the entrance examination to the University of Manchester in 1903 to study chemistry. He made this pursuit in spite of active discouragement by his parents. He gained his first-class hono ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Charles Glen King
Charles Glen King (October 22, 1896 – January 23, 1988) was an American biochemist who was a pioneer in the field of nutrition research and who isolated vitamin C at the same time as Albert Szent-Györgyi. A biography of King states that many feel he deserves equal credit with Szent-Györgyi for the discovery of this vitamin. Life King was born in Entiat, Washington to Charles Clement King and Mary Jane Bookwalter.http://jn.nutrition.org/content/118/11/1272.full.pdf He entered Washington State University early, as his local one-room school did not have a twelfth grade. He was a Member of Lambda Chi Alpha. World War I interrupted his college studies, where he served in the 12th Infantry, a machine gun company. He did not receive his B.S. in chemistry until 1918. He immediately departed for the University of Pittsburgh, earning his M.S. in 1920 and Ph.D. in 1923. From the outset of his graduate studies, the nascent field of vitamins interested him. He remained in Pittsburgh ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
