In organic chemistry, an amide known as an organic amide or a carboxamide, is a compound with the general formula RCNR′R″, where R, R′, R″ represent organic groups or hydrogen atoms. It can be viewed as a derivative of a carboxylic acid RCOH with the hydroxyl group –OH replaced by an amine group –NR′R″. Common examples of amides are acetamide H3C–CONH2, benzamide C6H5–CONH2, dimethylformamide HCON2. Amides are qualified as primary and tertiary according to whether the amine subgroup has the form –NH2, –NHR, or –NRR′, where R and R′ are groups other than hydrogen; the core –CN= of amides is called the amide group. Amides are pervasive in technology. Proteins and important plastics like Nylons, Aramid and Kevlar are polymers whose units are connected by amide groups. Amides include many other important biological compounds, as well as many drugs like paracetamol, penicillin and LSD. Low molecular weight amides, such as dimethylformamide, are common solvents. In the usual nomenclature, one adds the term "amide" to the stem of the parent acid's name.
For instance, the amide derived from acetic acid is named acetamide. IUPAC recommends ethanamide, but this and related formal names are encountered; when the amide is derived from a primary or secondary amine, the substituents on nitrogen are indicated first in the name. Thus, the amide formed from dimethylamine and acetic acid is N,N-dimethylacetamide; this name is simplified to dimethylacetamide. Cyclic amides are called lactams; the term "amide" or. Some chemists use different pronunciations for the two main senses, saying for the carbonyl–nitrogen compound and for the anion. Others replace one of these with; the lone pair of electrons on the nitrogen atom is delocalized into the carbonyl group, thus forming a partial double bond between nitrogen and carbon. In fact the O, C and N atoms have molecular orbitals occupied by delocalized electrons, forming a conjugated system; the three bonds of the nitrogen in amides is not pyramidal but planar. The structure of an amide can be described as a resonance between two alternative structures: It is estimated that acetamide has structure A for 62% of the time, B for 28% of the time.
There is a hydrogen bond present between the active groups hydrogen and nitrogen atoms. Resonance is prevented in the strained quinuclidone. Compared to amines, amides are weak bases. While the conjugate acid of an amine has a pKa of about 9.5, the conjugate acid of an amide has a pKa around −0.5. Therefore, amides don't have as noticeable acid–base properties in water; this relative lack of basicity is explained by the withdrawing of electrons from the amine by the carbonyl. On the other hand, amides are much stronger bases than carboxylic acids, esters and ketones; the proton of a primary or secondary amide does not dissociate under normal conditions. Conversely, under acidic conditions, the carbonyl oxygen can become protonated with a pKa of −1, it is not only because of the positive charge on the nitrogen, but because of the negative charge on the oxygen gained through resonance. Because of the greater electronegativity of oxygen, the carbonyl is a stronger dipole than the N–C dipole; the presence of a C=O dipole and, to a lesser extent a N–C dipole, allows amides to act as H-bond acceptors.
In primary and secondary amides, the presence of N–H dipoles allows amides to function as H-bond donors as well. Thus amides can participate in hydrogen bonding with water and other protic solvents; as a result of interactions such as these, the water solubility of amides is greater than that of corresponding hydrocarbons. These hydrogen bonds are have an important role in the secondary structure of proteins; the solubilities of amides and esters are comparable. Amides are less soluble than comparable amines and carboxylic acids since these compounds can both donate and accept hydrogen bonds. Tertiary amides, with the important exception of N,N-dimethylformamide, exhibit low solubility in water; the presence of the amide group –CN– is easily established, at least in small molecules. It can be distinguished from cyano groups in IR spectra. Amides exhibit a moderately intense νCO band near 1650 cm−1. By 1H NMR spectroscopy, CONHR signals occur at low fields. In X-ray crystallography, the CN center together with the three adjacent atoms characteristically define a plane.
Amides undergo many chemical reactions. Amides hydrolyse in hot alkali as well as in strong acidic conditions. Acidic conditions yield the carboxylic acid and the ammonium ion while basic hydrolysis yield the carboxylate ion and ammonia. Amides are versatile precursors to many other functional groups. Electrophiles attack the carbonyl oxygen; this step precedes hydrolysis, catalyzed by bo
Wang Xiaosong is a Chinese artist and professor. Having studied in Beijing and Berlin from 1983 to 1997, Wang uses a confluence of Chinese and Western art in his works. Wang was born in Wuhan, Hubei in 1964. After the beginning of the Cultural Revolution in 1966, his father was involved, while Wang returned to his hometown in Dalian, Liaoning in 1969. Since childhood, Wang was fond of creating clay figures, his grandfather and grandmother were a housewife, respectively. His mother was a singer in Wuhan. One of his uncles played the piano, another played the flute, his aunt was a dancer. Wang noted in an interview that his "living environment was full of the arts". Wang began to learn calligraphy as a teenager, he attended Wuhan Experimental School, where he "practiced sketching and colors". In 1983, he began his studies at the Central Academy of Arts & Design in Beijing—now known as the Academy of Arts and Design at Tsinghua University. Under the supervision of professors Liu Jude and Yu Binnan, Wang majored in Book Decoration, graduating in 1987.
In 1990, Wang moved to Berlin, where he majored in Visual Communication at the Berlin University of the Arts with professors Spohn and Bernhard Boës. In 1992, he settled in Berlin, working as designer. In 1994, Wang was accepted as a member of the German Artists Society. In 1996, he became a Director and Cultural General Supervisor at the Germany-China Cultural Exchanges Association. From 1997 to 2003, he taught at Victor Gollancz Volkshochschule Steglitz in Berlin. In 2003, he moved back to China and has since served as a doctoral advisor and dean of the Visual Communication Design Department in the Academy of Fine Arts at Zhejiang University. In addition to his activities as an artist and lecturer, Wang, in cooperation with Berlin architect Peter Ruge, maintains an architectural office in Hangzhou, where numerous new buildings and urban designs are conceived and realized. In 2011, Wang's work, Making Life, was shown at the Venice Biennale. Making Life was conceived as an antithesis to the official Chinese pavilion, attracted media attention.
Wang's works are part of various notable collections, such as the National Art Museum of China, the Ludwig Museum Koblenz, the Wiener Künstlerhaus. Wang is represented in Europe by the Schütz Fine Art gallery in Vienna. Wang is an abstractionist, his style has been described as "breaking the boundary between painting and sculpture". Wang's early work occupies an ambivalent middle ground between the figurative. In some of his works, such as Offenes China, cuts similar to those used by Lucio Fontana break the unity of the canvas, giving it a three-dimensional dynamic; the concepts of generation and decease are central in Wang's oeuvre, which becomes political when it addresses overpopulation, mass control, uniformity. In Wang's works, such as Ohne Titel, these themes remain at the center of his oeuvre. However, for the artist, there is no more need to rely on representative symbols of birth and annihilation, such as cuts and people. Art Vienna, Austria, Schütz Fine Art-Chinese Department, 2019 Art & Antique Hofburg Wien, Austria, Schütz Fine Art-Chinese Department, 2018 FAIR FOR ART VIENNA, Austria, Schütz Fine Art-Chinese Department, 2018 Art & Antique Hofburg Wien, Austria, Schütz Fine Art-Chinese Department, 2017 Art & Antique Residenz Salzburg, Austria, Schütz Fine Art-Chinese Department, 2016 Art Salzburg, Austria, Schütz Fine Art-Chinese Department, 2016 WIKAM Fair at the Künstlerhaus Vienna, Austria, Schütz Fine Art-Chinese Department, 2015 Art & Antique Hofburg Wien, Austria, Schütz Fine Art-Chinese Department, 2015 Art & Antique Residenz Salzburg, Austria, Schütz Fine Art-Chinese Department, 2015 Olympia International Art & Antiques Fair, London, UK, Schütz Fine Art-Chinese Department, 2015 Olympia International Art & Antiques Fair, London, UK, Schütz Fine Art-Chinese Department, 2014 LAPADA Art & Antiques Fair, London, UK, Schütz Fine Art, Schütz Fine Art-Chinese Department, 2014 ART.
FAIR Köln, Germany, Schütz Fine Art-Chinese Department, 2014 Art Salzburg, Austria, Schütz Fine Art-Chinese Department, 2014 Art Beijing, Art Solo 14, Taipei, 2014 China Arte Brasil, São Paulo, Brazil, 2014 Wang Xiaosong, Solo Exhibition, Pine's Art Gallery, Taipei, 2013 Unruly Ants, Künstlerhaus Wien, Austria, 2012-2013 Unruly Ants, Pallazzo Medici Riccardi, Italy, 2012-2013 Unruly Ants, Ludwig Museum, Germany, 2012-2013 Unruly Ants, Kunsthalle St. Annen, Lübeck, Germany, 2012-2013 Art & Antique Residenz Salzburg, Austria, Schütz Fine Art-Chinese Department, 2012 54. Biennale dell’Arte 2011, Italy, 2011 Empty Layer: Wang Xiaosong, Shanghai Duolun Museum of Modern Art, China, 2009 Interaction: Exhibition of Contemporary Chinese Oil Paintings, Wuhan Art Museum, China, 2008 Mix & Match Vision: Invitation for 2008, Contemporary Art Communication across Taiwan Straits, Wu Jiao Chao 800 Art Space, China, 2008 Exhibition of HD Schrader & Wang Xiaosong, Art Studio, Germany, 2007 Art Beijing 2007, China, 2007 „Return“.
The Cathedral of Burgo de Osma is a Roman Catholic church located in El Burgo de Osma, central Spain. It is in the Gothic architectural style, was constructed on an area occupied by a Romanesque church, it is one of the best preserved medieval buildings in the country and considered one of the best examples of thirteenth-century gothic architecture in Spain. The building of the church started in 1232, was completed in 1784; the cloister is from 1512. The tower is from 1739; the cathedral is dedicated to the Assumption of Mary. It is the seat of the Bishop of Osma. Among them is a Commentary on the Apocalypse from 1086