Nineteenth century

In the period 1775-1780, Lavoisier established chemistry as a quantitative science by proving that in the course of a chemical reaction the total mass is unaltered. The conservation of mass in chemical reactions proved ultimately to be a death blow to the phlogiston theory. Shortly after Lavoisier, Proust and Dalton proposed the laws of definite and multiple proportions. In 1803 Dalton proposed his atomic theory. Matter was made up of very small particles called atoms. Ever kind of atom has a definite weight. The atoms of different elements have different weights. Compounds are formed by atoms which combine in definite ratios of (usually small) whole numbers. This theory could give a satisfying interpretation of the quantitative data available at the time. 

This would require a ratio of atomic weights N/O = 7/12. No compound of nitrogen and oxygen exhibiting such a ratio of combining weights was known. 

In the late 1850s the kinetic theory of gases was intensively developed and met with phenomenal success. Kinetic theory is based on the atomic hypothesis and depends importantly on Rumford s idea of the relation between heat and motion. 

The chemical achievements, particularly in synthetic and analytical chemistry, in the 19th century are staggering in number we mention only a few. The growth of organic chemistry after Wohler s synthesis of urea, 1824. The stereochemical studies of van t Hoff, LeBel, and Pasteur. The chemical proof of the tetrahedral arrangement of the bonds about 

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It was known in the sixteenth century that silver salts were photosensitive, but it was not until the beginning of the nineteenth century, when Herschel found that silver chloride was soluble in sodium thiosulphate, that photography became possible. 

In the late nineteenth century, Wien analyzed experimental data on blackbody radiation and found that the maximum of the blackbody radiation specti um shifts with the temperature according to the equation... 

In the nineteenth century. Merling treated eyeloheptatriene with bromine and obtained a crystalline solid. Reasoning from some information gained in working Problem 15. what might this solid be ... 

In the mid-nineteenth century, the empirical formula of benzene, was known but its structural formula was tiot. Two proposed structures... 

In the nineteenth century, scientists showed that many substances, such as oxygen and carbon, had a smallest recognizable constituent... 

The dawn of the nineteenth century saw a drastic shift from the dominance of French chemistry to first English-, and, later, German-influenced chemistry. Lavoisier s dualistic views of chemical composition and his explanation of combustion and acidity were landmarks but hardly made chemistry an exact science. Chemistry remained in the nineteenth century basically qualitative in its nature. Despite the Newtonian dream of quantifying the forces of attraction between chemical substances and compiling a table of chemical affinity, no quantitative generalization emerged. It was Dalton s chemical atomic theory and the laws of chemical combination explained by it that made chemistry an exact science. 

For two thousand years atoms were considered the smallest and indivisible units of nature. At the beginning of the nineteenth century Dalton got chemistry on the path of atomic theory with his book, A New System of Chemical Philosophy, in which he argued that unbreakable atoms form compounds by linking with other atoms in simple... 

Ethylene (as well as propylene) produced from carbon dioxide subsequently allows ready preparation of the whole array of hydrocarbons, as well as their derivatives and products that have become essential to our everyday life. Whereas the nineteenth century relied mostly on coal for energy as well as derived chemical products, the twentieth century greatly supplemented this with petroleum and nat-... 

The University of Kazan was home to a number of promi nent nineteenth century or game chemists Their contributions are recognized in two articles published in the January and February 1994 issues of the Joc/rna/of Chemical Education (pp 39 2 and 93-98)... 

Hydrocarbons are divided into two mam classes aliphatic and aromatic This classifi cation dates from the nineteenth century when organic chemistry was devoted almost entirely to the study of materials from natural sources and terms were coined that reflected a substance s origin Two sources were fats and oils and the word aliphatic was derived from the Greek word aleiphar meaning ( fat ) Aromatic hydrocarbons irre spective of their own odor were typically obtained by chemical treatment of pleasant smelling plant extracts... 

During the nineteenth century it was widely believed—incorrectly as we 11 soon see— that cycloalkane rings are planar A leading advocate of this view was the German chemist Adolf von Baeyer He noted that compounds containing rings other than those... 

Fischer was the foremost or game chemist of the late nineteenth century He won the 1902 Nobel Prize in chemistry for his pioneering work in carbohydrate and protein chemistry... 

Acetylene was discovered m 1836 by Edmund Davy and characterized by the French chemist P E M Berthelot m 1862 It did not command much attention until its large scale preparation from calcium carbide m the last decade of the nineteenth century stim ulated interest m industrial applications In the first stage of that synthesis limestone and coke a material rich m elemental carbon obtained from coal are heated m an electric furnace to form calcium carbide... 

The SI units of frequency are reciprocal seconds (s ) given the name hertz and the symbol Hz m honor of the nineteenth century physicist Heinrich R Hertz The constant of proportionality h is called Planck s constant and has the value... 

Divalent carbon species first received attention with the work of the Swiss American chemist J U Nef in the late nineteenth century they were then largely ignored until the 1950s... 

Ludwig Claisen was a Ger man chemist who worked during the last two decades of the nineteenth century and the first two decades of the twentieth His name is associated with three reac tions The Claisen-Schmidt reaction was presented in Section 18 10 the Claisen condensation is discussed in this section and the C/a/sen rearrangement will be intro duced in Section 24 13... 

This reaction is known as the Hofmann elimination, it was developed by August W Hofmann m the middle of the nineteenth century and is both a synthetic method to pre pare alkenes and an analytical tool for structure determination... 

Phenol was first isolated m the early nineteenth century from coal tar and a small por tion of the more than 4 billion lb of phenol produced m the United States each year comes from this source Although significant quantities of phenol are used to prepare aspirin and dyes most of it is converted to phenolic resins used m adhesives and plastics... 

The key compound m the synthesis of aspirin salicylic acid is prepared from phe nol by a process discovered m the nineteenth century by the German chemist Hermann Kolbe In the Kolbe synthesis also known as the Kolbe—Schmitt reaction, sodium phen oxide IS heated with carbon dioxide under pressure and the reaction mixture is subse quently acidified to yield salicylic acid... 

One of the oldest methods for the synthesis of ammo acids dates back to the nineteenth century and is simply a nucleophilic substitution m which ammonia reacts with an a halo carboxylic acid... 

Baeyer strain theory (Section 3 4) Incorrect nineteenth century theory that considered the nngs of cycloalkanes to be planar and assessed their stabilities according to how much the angles of a corresponding regular polygon devi ated from the tetrahedral value of 109 5°... 

Developments in equilibrium theory in the late nineteenth century led to significant improvements in the theoretical understanding of acid-base chemistry and. 

Colorimetry, in which a sample absorbs visible light, is one example of a spectroscopic method of analysis. At the end of the nineteenth century, spectroscopy was limited to the absorption, emission, and scattering of visible, ultraviolet, and infrared electromagnetic radiation. During the twentieth century, spectroscopy has been extended to include other forms of electromagnetic radiation (photon spectroscopy), such as X-rays, microwaves, and radio waves, as well as energetic particles (particle spectroscopy), such as electrons and ions. ... 

The earliest examples of analytical methods based on chemical kinetics, which date from the late nineteenth century, took advantage of the catalytic activity of enzymes. Typically, the enzyme was added to a solution containing a suitable substrate, and the reaction between the two was monitored for a fixed time. The enzyme s activity was determined by measuring the amount of substrate that had reacted. Enzymes also were used in procedures for the quantitative analysis of hydrogen peroxide and carbohydrates. The application of catalytic reactions continued in the first half of the twentieth century, and developments included the use of nonenzymatic catalysts, noncatalytic reactions, and differences in reaction rates when analyzing samples with several analytes. 

During the late nineteenth century evidence began to accumulate that classical newtonian mechanics, which was completely successful on a macroscopic scale, was unsuccessful when applied fo problems on an atomic scale. 

Furfural was first isolated in the eady nineteenth century. Dobereiner is credited with the discovery. He obtained a small amount of a yellow "oil" (too Htde to characterize) as a by-product in the preparation of formic acid (8). Other chemists found that the same "oil" having a charactedstic aroma could be obtained by boiling finely divided vegetable materials such as oats, com, sawdust, bran, etc, with aqueous sulfuric acid or other acids (9,10). The oil was present in the Hquid resulting from condensation of the vapors produced during heating. The empirical formula was determined by Stenhouse... 

Classical and Quantum Mechanics. At the beginning of the twentieth century, a revolution was brewing in the world of physics. For hundreds of years, the Newtonian laws of mechanics had satisfactorily provided explanations and supported experimental observations in the physical sciences. However, the experimentaUsts of the nineteenth century had begun delving into the world of matter at an atomic level. This led to unsatisfactory explanations of the observed patterns of behavior of electricity, light, and matter, and it was these inconsistencies which led Bohr, Compton, deBroghe, Einstein, Planck, and Schrn dinger to seek a new order, another level of theory, ie, quantum theory. 

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