Chemistry is the scientific discipline involved with elements and compounds composed of atoms and ions: their composition, properties and the changes they undergo during a reaction with other substances. In the scope of its subject, chemistry occupies an intermediate position between physics and biology, it is sometimes called the central science because it provides a foundation for understanding both basic and applied scientific disciplines at a fundamental level. For example, chemistry explains aspects of plant chemistry, the formation of igneous rocks, how atmospheric ozone is formed and how environmental pollutants are degraded, the properties of the soil on the moon, how medications work, how to collect DNA evidence at a crime scene. Chemistry addresses topics such as how atoms and molecules interact via chemical bonds to form new chemical compounds. There are four types of chemical bonds: covalent bonds, in which compounds share one or more electron; the word chemistry comes from alchemy, which referred to an earlier set of practices that encompassed elements of chemistry, philosophy, astronomy and medicine.
It is seen as linked to the quest to turn lead or another common starting material into gold, though in ancient times the study encompassed many of the questions of modern chemistry being defined as the study of the composition of waters, growth, disembodying, drawing the spirits from bodies and bonding the spirits within bodies by the early 4th century Greek-Egyptian alchemist Zosimos. An alchemist was called a'chemist' in popular speech, the suffix "-ry" was added to this to describe the art of the chemist as "chemistry"; the modern word alchemy in turn is derived from the Arabic word al-kīmīā. In origin, the term is borrowed from the Greek χημία or χημεία; this may have Egyptian origins since al-kīmīā is derived from the Greek χημία, in turn derived from the word Kemet, the ancient name of Egypt in the Egyptian language. Alternately, al-kīmīā may derive from χημεία, meaning "cast together"; the current model of atomic structure is the quantum mechanical model. Traditional chemistry starts with the study of elementary particles, molecules, metals and other aggregates of matter.
This matter can be studied in isolation or in combination. The interactions and transformations that are studied in chemistry are the result of interactions between atoms, leading to rearrangements of the chemical bonds which hold atoms together; such behaviors are studied in a chemistry laboratory. The chemistry laboratory stereotypically uses various forms of laboratory glassware; however glassware is not central to chemistry, a great deal of experimental chemistry is done without it. A chemical reaction is a transformation of some substances into one or more different substances; the basis of such a chemical transformation is the rearrangement of electrons in the chemical bonds between atoms. It can be symbolically depicted through a chemical equation, which involves atoms as subjects; the number of atoms on the left and the right in the equation for a chemical transformation is equal. The type of chemical reactions a substance may undergo and the energy changes that may accompany it are constrained by certain basic rules, known as chemical laws.
Energy and entropy considerations are invariably important in all chemical studies. Chemical substances are classified in terms of their structure, phase, as well as their chemical compositions, they can be analyzed using the tools of e.g. spectroscopy and chromatography. Scientists engaged in chemical research are known as chemists. Most chemists specialize in one or more sub-disciplines. Several concepts are essential for the study of chemistry; the particles that make up matter have rest mass as well – not all particles have rest mass, such as the photon. Matter can be a mixture of substances; the atom is the basic unit of chemistry. It consists of a dense core called the atomic nucleus surrounded by a space occupied by an electron cloud; the nucleus is made up of positively charged protons and uncharged neutrons, while the electron cloud consists of negatively charged electrons which orbit the nucleus. In a neutral atom, the negatively charged electrons balance out the positive charge of the protons.
The nucleus is dense. The atom is the smallest entity that can be envisaged to retain the chemical properties of the element, such as electronegativity, ionization potential, preferred oxidation state, coordination number, preferred types of bonds to form. A chemical element is a pure substance, composed of a single type of atom, characterized by its particular number of protons in the nuclei of its atoms, known as the atomic number and represented by the symbol Z; the mass number is the sum of the number of neutrons in a nucleus. Although all the nuclei of all atoms belonging to one element will have the same
Ludwig Maximilian University of Munich
Ludwig Maximilian University of Munich is a public research university located in Munich, Germany. The University of Munich is Germany's sixth-oldest university in continuous operation. Established in Ingolstadt in 1472 by Duke Ludwig IX of Bavaria-Landshut, the university was moved in 1800 to Landshut by King Maximilian I of Bavaria when Ingolstadt was threatened by the French, before being relocated to its present-day location in Munich in 1826 by King Ludwig I of Bavaria. In 1802, the university was named Ludwig-Maximilians-Universität by King Maximilian I of Bavaria in his as well as the university's original founder's honour; the University of Munich has since the 19th century, been considered as one of Germany's as well as one of Europe's most prestigious universities. Among these were Wilhelm Röntgen, Max Planck, Werner Heisenberg, Otto Hahn and Thomas Mann. Pope Benedict XVI was a student and professor at the university; the LMU has been conferred the title of "elite university" under the German Universities Excellence Initiative.
LMU is the second-largest university in Germany in terms of student population. Of these, 8,671 were freshmen while international students totalled 7,812 or 15% of the student population; as for operating budget, the university records in 2015 a total of 660.0 million euros in funding without the university hospital. The University was founded with papal approval in 1472 as the University of Ingolstadt, with faculties of philosophy, medicine and theology, its first rector was Christopher Mendel of Steinfels, who became bishop of Chiemsee. In the period of German humanism, the university's academics included names such as Conrad Celtes and Petrus Apianus; the theologian Johann Eck taught at the university. From 1549 to 1773, the university was influenced by the Jesuits and became one of the centres of the Counter-Reformation; the Jesuit Petrus Canisius served as rector of the university. At the end of the 18th century, the university was influenced by the Enlightenment, which led to a stronger emphasis on natural science.
In 1800, the Prince-Elector Maximilian IV Joseph moved the university to Landshut, due to French aggression that threatened Ingolstadt during the Napoleonic Wars. In 1802, the university was renamed the Ludwig Maximilian University in honour of its two founders, Louis IX, Duke of Bavaria and Maximilian I, Elector of Bavaria; the Minister of Education, Maximilian von Montgelas, initiated a number of reforms that sought to modernize the rather conservative and Jesuit-influenced university. In 1826, it was moved to the capital of the Kingdom of Bavaria; the university was situated in the Old Academy until a new building in the Ludwigstraße was completed. The locals were somewhat critical of the number of Protestant professors Maximilian and Ludwig I invited to Munich, they were dubbed the "Nordlichter" and physician Johann Nepomuk von Ringseis was quite angry about them. In the second half of the 19th century, the university rose to great prominence in the European scientific community, attracting many of the world's leading scientists.
It was a period of great expansion. From 1903, women were allowed to study at Bavarian universities, by 1918, the female proportion of students at LMU had reached 18%. In 1918, Adele Hartmann became the first woman in Germany to earn the Habilitation, at LMU. During the Weimar Republic, the university continued to be one of the world's leading universities, with professors such as Wilhelm Röntgen, Wilhelm Wien, Richard Willstätter, Arnold Sommerfeld and Ferdinand Sauerbruch. During the Third Reich, academic freedom was curtailed. In 1943 the White Rose group of anti-Nazi students conducted their campaign of opposition to the National Socialists at this university; the university has continued to be one of the leading universities of West Germany during the Cold War and in the post-reunification era. In the late 1960s, the university was the scene of protests by radical students. Today the University of Munich is part of 24 Collaborative Research Centers funded by the German Research Foundation and is host university of 13 of them.
It hosts 12 DFG Research Training Groups and three international doctorate programs as part of the Elite Network of Bavaria. It attracts an additional 120 million euros per year in outside funding and is intensively involved in national and international funding initiatives. LMU Munich has a wide range of degree programs, with 150 subjects available in numerous combinations. 15% of the 45,000 students who attend the university come from abroad. In 2005, Germany’s state and federal governments launched the German Universities Excellence Initiative, a contest among its universities. With a total of 1.9 billion euros, 75 percent of which comes from the federal state, its architects aim to strategically promote top-level research and scholarship. The money is given to more than 30 research universities in Germany; the initiative will fund three project-oriented areas: graduate schools to promote the next generation of scholars, clusters of excellence to promote cutting-edge research and "future concepts" for the project-based expansion of academic excellence at universities as a whole.
In order to
Physics is the natural science that studies matter, its motion, behavior through space and time, that studies the related entities of energy and force. Physics is one of the most fundamental scientific disciplines, its main goal is to understand how the universe behaves. Physics is one of the oldest academic disciplines and, through its inclusion of astronomy the oldest. Over much of the past two millennia, chemistry and certain branches of mathematics, were a part of natural philosophy, but during the scientific revolution in the 17th century these natural sciences emerged as unique research endeavors in their own right. Physics intersects with many interdisciplinary areas of research, such as biophysics and quantum chemistry, the boundaries of physics which are not rigidly defined. New ideas in physics explain the fundamental mechanisms studied by other sciences and suggest new avenues of research in academic disciplines such as mathematics and philosophy. Advances in physics enable advances in new technologies.
For example, advances in the understanding of electromagnetism and nuclear physics led directly to the development of new products that have transformed modern-day society, such as television, domestic appliances, nuclear weapons. Astronomy is one of the oldest natural sciences. Early civilizations dating back to beyond 3000 BCE, such as the Sumerians, ancient Egyptians, the Indus Valley Civilization, had a predictive knowledge and a basic understanding of the motions of the Sun and stars; the stars and planets were worshipped, believed to represent gods. While the explanations for the observed positions of the stars were unscientific and lacking in evidence, these early observations laid the foundation for astronomy, as the stars were found to traverse great circles across the sky, which however did not explain the positions of the planets. According to Asger Aaboe, the origins of Western astronomy can be found in Mesopotamia, all Western efforts in the exact sciences are descended from late Babylonian astronomy.
Egyptian astronomers left monuments showing knowledge of the constellations and the motions of the celestial bodies, while Greek poet Homer wrote of various celestial objects in his Iliad and Odyssey. Natural philosophy has its origins in Greece during the Archaic period, when pre-Socratic philosophers like Thales rejected non-naturalistic explanations for natural phenomena and proclaimed that every event had a natural cause, they proposed ideas verified by reason and observation, many of their hypotheses proved successful in experiment. The Western Roman Empire fell in the fifth century, this resulted in a decline in intellectual pursuits in the western part of Europe. By contrast, the Eastern Roman Empire resisted the attacks from the barbarians, continued to advance various fields of learning, including physics. In the sixth century Isidore of Miletus created an important compilation of Archimedes' works that are copied in the Archimedes Palimpsest. In sixth century Europe John Philoponus, a Byzantine scholar, questioned Aristotle's teaching of physics and noting its flaws.
He introduced the theory of impetus. Aristotle's physics was not scrutinized until John Philoponus appeared, unlike Aristotle who based his physics on verbal argument, Philoponus relied on observation. On Aristotle's physics John Philoponus wrote: “But this is erroneous, our view may be corroborated by actual observation more than by any sort of verbal argument. For if you let fall from the same height two weights of which one is many times as heavy as the other, you will see that the ratio of the times required for the motion does not depend on the ratio of the weights, but that the difference in time is a small one, and so, if the difference in the weights is not considerable, that is, of one is, let us say, double the other, there will be no difference, or else an imperceptible difference, in time, though the difference in weight is by no means negligible, with one body weighing twice as much as the other”John Philoponus' criticism of Aristotelian principles of physics served as an inspiration for Galileo Galilei ten centuries during the Scientific Revolution.
Galileo cited Philoponus in his works when arguing that Aristotelian physics was flawed. In the 1300s Jean Buridan, a teacher in the faculty of arts at the University of Paris, developed the concept of impetus, it was a step toward the modern ideas of momentum. Islamic scholarship inherited Aristotelian physics from the Greeks and during the Islamic Golden Age developed it further placing emphasis on observation and a priori reasoning, developing early forms of the scientific method; the most notable innovations were in the field of optics and vision, which came from the works of many scientists like Ibn Sahl, Al-Kindi, Ibn al-Haytham, Al-Farisi and Avicenna. The most notable work was The Book of Optics, written by Ibn al-Haytham, in which he conclusively disproved the ancient Greek idea about vision, but came up with a new theory. In the book, he presented a study of the phenomenon of the camera obscura (his thousand-year-old
A chemist is a scientist trained in the study of chemistry. Chemists study the composition of its properties. Chemists describe the properties they study in terms of quantities, with detail on the level of molecules and their component atoms. Chemists measure substance proportions, reaction rates, other chemical properties; the word'chemist' is used to address Pharmacists in Commonwealth English. Chemists use this knowledge to learn the composition and properties of unfamiliar substances, as well as to reproduce and synthesize large quantities of useful occurring substances and create new artificial substances and useful processes. Chemists may specialize in any number of subdisciplines of chemistry. Materials scientists and metallurgists share skills with chemists; the work of chemists is related to the work of chemical engineers, who are concerned with the proper design and evaluation of the most cost-effective large-scale chemical plants and work with industrial chemists on the development of new processes and methods for the commercial-scale manufacture of chemicals and related products.
The roots of chemistry can be traced to the phenomenon of burning. Fire was a mystical force that transformed one substance into another and thus was of primary interest to mankind, it was fire. After gold was discovered and became a precious metal, many people were interested to find a method that could convert other substances into gold; this led to the protoscience called alchemy. The word chemist is derived from an abbreviation of alchimista. Alchemists discovered many chemical processes. Chemistry as we know it today, was invented by Antoine Lavoisier with his law of conservation of mass in 1783; the discoveries of the chemical elements has a long history culminating in the creation of the periodic table by Dmitri Mendeleev. The Nobel Prize in Chemistry created in 1901 gives an excellent overview of chemical discovery since the start of the 20th century. Jobs for chemists require at least a bachelor's degree, but many positions those in research, require a Master of Science or a Doctor of Philosophy.
Most undergraduate programs emphasize mathematics and physics as well as chemistry because chemistry is known as "the central science", thus chemists ought to have a well-rounded knowledge about science. At the Master's level and higher, students tend to specialize in a particular field. Fields of specialization include biochemistry, nuclear chemistry, organic chemistry, inorganic chemistry, polymer chemistry, analytical chemistry, physical chemistry, theoretical chemistry, quantum chemistry, environmental chemistry, thermochemistry. Postdoctoral experience may be required for certain positions. Workers whose work involves chemistry, but not at a complexity requiring an education with a chemistry degree, are referred to as chemical technicians; such technicians do such work as simpler, routine analyses for quality control or in clinical laboratories, having an associate degree. A chemical technologist has more education or experience than a chemical technician but less than a chemist having a bachelor's degree in a different field of science with an associate degree in chemistry or having the same education as a chemical technician but more experience.
There are degrees specific to become a chemical technologist, which are somewhat distinct from those required when a student is interested in becoming a professional chemist. A Chemical technologist is more involved in the management and operation of the equipment and instrumentation necessary to perform chemical analyzes than a chemical technician, they are part of the team of a chemical laboratory in which the quality of the raw material, intermediate products and finished products is analyzed. They perform functions in the areas of environmental quality control and the operational phase of a chemical plant. In addition to all the training given to chemical technologists in their respective degree, a chemist is trained to understand more details related to chemical phenomena so that the chemist can be capable of more planning on the steps to achieve a distinct goal via a chemistry-related endeavor; the higher the competency level achieved in the field of chemistry, the higher the responsibility given to that chemist and the more complicated the task might be.
Chemistry, as a field, have so many applications that different tasks and objectives can be given to workers or scientists with these different levels of education or experience. The specific title of each job varies from position to position, depending on factors such as the kind of industry, the routine level of the task, the current needs of a particular enterprise, the size of the enterprise or hiring firm, the philosophy and management principles of the hiring firm, the visibility of the competency and individual achievements of the one seeking employment, economic factors such as recession or economic depression, among other factors, so this makes it difficult to categorize the exact roles of these chemistry-related workers as standard for that given level of education; because of these factors affecting exact job titles with distinct responsibilities, some chemists might begin doing technician tasks while other chemists might begin doing more complicated tasks than those of a technician, such as tasks th
The German Confederation was an association of 39 German-speaking states in Central Europe, created by the Congress of Vienna in 1815 to coordinate the economies of separate German-speaking countries and to replace the former Holy Roman Empire, dissolved in 1806. The German Confederation excluded German-speaking lands in the eastern portion of the Kingdom of Prussia, the German cantons of Switzerland, Alsace within France, majority German speaking; the Confederation was weakened by rivalry between the Kingdom of Prussia and the Austrian Empire and the inability of the multiple members to compromise. In 1848, revolutions by liberals and nationalists attempted to establish a unified German state with a progressive liberal constitution under the Frankfurt Convention; the ruling body, the Confederate Diet, was dissolved on 12 July 1848, but was re-established in 1850 after failed efforts to replace it. The Confederation was dissolved after the Prussian victory in the Seven Weeks' War over Austria in 1866.
The dispute over which had the inherent right to rule German lands ended in favour of Prussia, leading to the creation of the North German Confederation under Prussian leadership in 1867, to which the eastern portions of the Kingdom of Prussia were added. A number of South German states remained independent until they joined the North German Confederation, renamed and proclaimed as the "German Empire" in 1871 for the now unified Germany with the Prussian king as emperor after the victory over French Emperor Napoleon III in the Franco-Prussian War of 1870. Most historians have judged the Confederation to have been weak and ineffective, as well as an obstacle to the creation of a German nation-state. However, the Confederation was designed to be weak, as it served the interests of the European Great Powers member states Austria and Prussia; the War of the Third Coalition lasted from about 1803 to 1806. Following defeat at the Battle of Austerlitz by the French under Napoleon in December 1805, Holy Roman Emperor Francis II abdicated, the Empire was dissolved on 6 August 1806.
The resulting Treaty of Pressburg established the Confederation of the Rhine in July 1806, joining together sixteen of France's allies among the German states. After the Battle of Jena–Auerstedt of October 1806 in the War of the Fourth Coalition, various other German states, including Saxony and Westphalia joined the Confederation. Only Austria, Danish Holstein, Swedish Pomerania, the French-occupied Principality of Erfurt stayed outside the Confederation of the Rhine; the War of the Sixth Coalition from 1812 to winter 1814 saw the defeat of Napoleon and the liberation of Germany. In June 1814, the famous German patriot Heinrich vom Stein created the Central Managing Authority for Germany in Frankfurt to replace the defunct Confederation of the Rhine. However, plenipotentiaries gathered at the Congress of Vienna were determined to create a weaker union of German states than envisaged by Stein; the German Confederation was created by the 9th Act of the Congress of Vienna on 8 June 1815 after being alluded to in Article 6 of the 1814 Treaty of Paris, ending the War of the Sixth Coalition.
The Confederation was formally created by a second treaty, the Final Act of the Ministerial Conference to Complete and Consolidate the Organization of the German Confederation. This treaty was not concluded and signed by the parties until 15 May 1820. States joined the German Confederation by becoming parties to the second treaty; the states designated for inclusion in the Confederation were: Anhalt-Bernburg Anhalt-Dessau Anhalt-Köthen Austrian Empire Baden Bavaria Brunswick Hanover Electorate of Hesse Grand Duchy of Hesse Hohenzollern-Hechingen Hohenzollern-Sigmaringen Holstein and Lauenburg, held by Denmark Holstein-Oldenburg Liechtenstein Lippe-Detmold Luxembourg, held by the Netherlands Mecklenburg-Schwerin Mecklenburg-Strelitz Nassau Prussia Reuss, elder line Reuss, younger line Saxony Saxe-Weimar-Eisenach Saxe-Coburg Saxe-Gotha Saxe-Hildburghausen Saxe-Meiningen Schaumburg-Lippe Schwarzburg-Rudolstadt Schwarzburg-Sondershausen Waldeck Württemberg Hesse-Homburg Lübeck Frankfurt Bremen Hamburg In 1839, as compensation for the loss of the province of Luxemburg to Belgium, the Duchy of Limburg was created and it was a member of the German Confederation until its dissolution in 1866.
The cities of Maastricht and Venlo were not included in the Confederation. The Austrian Empire and the Kingdom of Prussia were the largest and by far the most powerful members of the Confederation. Large parts of both countries were not included in the Confederation, because they had not been part of the former Holy Roman Empire, nor had the greater parts of their armed forces been incorporated in the federal army. Austria and Prussia each had one vote in the Federal Assembly. Six other major states had one vote each in the Federal Ass
Ghent University is a public research university located in Ghent, Belgium. It was established in 1817 by King William I of the Netherlands. After the Belgian revolution of 1830, the newly formed Belgian state began to administer the university. In 1930, the university became the first Dutch-speaking university in Belgium, whereas French had been the standard academic language. In 1991,it was granted major autonomy and changed its name accordingly from State University of Ghent to its current designation. In contrast to the Catholic University of Leuven or the Free University of Brussels, UGent considers itself a pluralist university in a special sense, i.e. not connected to any particular religion or political ideology. Its motto Inter Utrumque, on the coat of arms, suggests the acquisition of wisdom and science comes only in an atmosphere of peace, when the institution is supported by the monarchy and fatherland. Ghent University is one of the biggest Flemish universities, consisting of 41,000 students and 9,000 staff members.
The University supports the University Library and the University Hospital, one of the largest hospitals in Belgium. It is one of the greatest beneficiaries of funding from the Research Foundation - Flanders. Ghent University rates among the top universities in the world; the university in Ghent was opened on October 9, 1817, with JC van Rotterdam serving as the first rector. In the first year, it had 16 professors; the original four faculties consisted of Humanities, Law and Science, the language of instruction was Latin. The university was founded by King William I as part of a policy to stem the intellectual and academic lag in the southern part of the United Kingdom of the Netherlands to become Belgium. After peaking at a student population of 414, the number of students declined following the Belgian Revolution. At this time, the Faculties of Humanities and Science were broken from the university, but they were restored five years in 1835. Ghent University played a big role in the foundation of modern organic chemistry.
Friedrich August Kekulé unraveled the structure of benzene at Ghent and Adolf von Baeyer, a student of August Kekulé, made seminal contributions to organic chemistry. In 1882, Sidonie Verhelst became the first female student at the university. French became the language of instruction, after the 1830 Revolution. In 1903, the Flemish politician Lodewijk De Raet led a successful campaign to begin instruction in Dutch, the first courses were begun in 1906. During World War I, the occupying German administration conducted Flamenpolitik and turned Ghent University into the first Dutch-speaking university in Belgium. A Flemish Institute known as Von Bissing University, was founded in 1916 but was disestablished after the war and French language was reinstated. In 1923, Cabinet Minister Pierre Nolf put forward a motion to definitively establish the university as a Dutch-speaking university, this was realized in 1930. August Vermeylen served as the first rector of a Dutch-language university in Belgium.
In the Second World War, the German administration of the university attempted to create a German orientation, removing faculty members and installing loyal activists. However, the university became the focal point for many resistance members. After the war, the university became a much larger institution, following government policy of democratizing higher education in Flanders during the 1950s and 1960s. By 1953, there were more than 3,000 students, by 1969 more than 11,500; the number of faculties increased to eleven, starting with Applied Sciences in 1957. It was followed by Economics and Veterinary Medicine in 1968, Psychology and Pedagogy, as well as Bioengineering, in 1969, Pharmaceutical Sciences; the faculty of Politics and Social Sciences is the most recent addition, in 1992. In the 1960s to 1980s, there were several student demonstrations at Ghent University, notably around the Blandijn site, which houses the Faculty of Arts & Philosophy; the severest demonstrations took place in 1969 in the wake of May 1968.
In 1991, the university changed its name from Rijksuniversiteit Gent to Universiteit Gent, following an increased grant of autonomy by the government of the Flemish Community. Ghent University consists of eleven Faculties with over 130 individual departments. In addition, the university maintains the Zwijnaarde science park and Greenbridge science park. Faculty of Arts and Philosophy Faculty of Bio-science Engineering Faculty of Law Faculty of Sciences Faculty of Medicine and Health Sciences Faculty of Engineering and Architecture Faculty of Economics and Business Administration Faculty of Veterinary Medicine Faculty of Psychology and Educational Sciences Faculty of Pharmaceutical Sciences Faculty of Political and Social Sciences Standing on the Blandijnberg, the Boekentoren houses the Ghent University Library, which contains nearly 3 million volumes; the University Library has joined the Google Books Library Project. Among other notable collections, it preserves Papyrus 30, an early manuscript of the Greek New Testament.
Ghent University ranks among the best universities in the world. Most in 2017, it was ranked, globally, 69th by the Academic Ranking of World Universities and 125th by QS World University Rankings. For 2018, Ghent University has been ranked, worldwide, 88th by U. S. News & World Report and 107th by Times Higher Education
Friedrich August Kekulé Friedrich August Kekule von Stradonitz, was a German organic chemist. From the 1850s until his death, Kekulé was one of the most prominent chemists in Europe in theoretical chemistry, he was the principal founder of the theory of chemical structure. Kekulé never used his first given name. After he was ennobled by the Kaiser in 1895, he adopted the name August Kekule von Stradonitz, without the French acute accent over the second "e"; the French accent had been added to the name by Kekulé's father during the Napoleonic occupation of Hesse by France, to ensure that French-speaking people pronounced the third syllable. The son of a civil servant, Kekulé was born in the capital of the Grand Duchy of Hesse. After graduating from secondary school, in the fall of 1847 he entered the University of Giessen, with the intention of studying architecture. After hearing the lectures of Justus von Liebig in his first semester, he decided to study chemistry. Following four years of study in Giessen and a brief compulsory military service, he took temporary assistantships in Paris, in Chur, in London, where he was decisively influenced by Alexander Williamson.
His Giessen doctoral degree was awarded in the summer of 1852. In 1856 Kekulé became Privatdozent at the University of Heidelberg. In 1858 he was hired as full professor at the University of Ghent in 1867 he was called to Bonn, where he remained for the rest of his career. Basing his ideas on those of predecessors such as Williamson, Edward Frankland, William Odling, Auguste Laurent, Charles-Adolphe Wurtz and others, Kekulé was the principal formulator of the theory of chemical structure; this theory proceeds from the idea of atomic valence the tetravalence of carbon and the ability of carbon atoms to link to each other, to the determination of the bonding order of all of the atoms in a molecule. Archibald Scott Couper independently arrived at the idea of self-linking of carbon atoms, provided the first molecular formulas where lines symbolize bonds connecting the atoms. For organic chemists, the theory of structure provided dramatic new clarity of understanding, a reliable guide to both analytic and synthetic work.
As a consequence, the field of organic chemistry developed explosively from this point. Among those who were most active in pursuing early structural investigations were, in addition to Kekulé and Couper, Wurtz, Alexander Crum Brown, Emil Erlenmeyer, Alexander Butlerov. Kekulé's idea of assigning certain atoms to certain positions within the molecule, schematically connecting them using what he called their "Verwandtschaftseinheiten", was based on evidence from chemical reactions, rather than on instrumental methods that could peer directly into the molecule, such as X-ray crystallography; such physical methods of structural determination had not yet been developed, so chemists of Kekulé's day had to rely entirely on so-called "wet" chemistry. Some chemists, notably Hermann Kolbe criticized the use of structural formulas that were offered, as he thought, without proof. However, most chemists followed Kekulé's lead in pursuing and developing what some have called "classical" structure theory, modified after the discovery of electrons and the development of quantum mechanics.
The idea that the number of valences of a given element was invariant was a key component of Kekulé's version of structural chemistry. This generalization suffered from many exceptions, was subsequently replaced by the suggestion that valences were fixed at certain oxidation states. For example, periodic acid according to Kekuléan structure theory could be represented by the chain structure I-O-O-O-O-H. By contrast, the modern structure of periodic acid has all four oxygen atoms surrounding the iodine in a tetrahedral geometry. Kekulé's most famous work was on the structure of benzene. In 1865 Kekulé published a paper in French suggesting that the structure contained a six-membered ring of carbon atoms with alternating single and double bonds; the following year he published a much longer paper in German on the same subject. The empirical formula for benzene had been long known, but its unsaturated structure was a challenge to determine. Archibald Scott Couper in 1858 and Joseph Loschmidt in 1861 suggested possible structures that contained multiple double bonds or multiple rings, but the study of aromatic compounds was in its earliest years, too little evidence was available to help chemists decide on any particular structure.
More evidence was available by 1865 regarding the relationships of aromatic isomers. Kekulé argued for his proposed structure by considering the number of isomers observed for derivatives of benzene. For every monoderivative of benzene only one isomer was found, implying that all six carbons are equivalent, so that substitution on any carbon gives only a single possible product. For diderivatives such as the toluidines, C6H4, three isomers were observed, for which Kekulé proposed structures with the two substituted carbon atoms separated by one and three carbon-carbon bonds named ortho and para isomers respectively; the counting of possible isomers for diderivatives was however criticized by Albert Ladenburg, a for