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Group Contribution Method
A group-contribution method in chemistry is a technique to estimate and predict thermodynamic and other properties from molecular structures. Introduction In today's chemical processes hundreds of thousands of components are used. The Chemical Abstracts Service registry lists 56 million substances, but many of these are only of scientific interest. Process designers need to know some basic chemical properties of the components and their mixtures. Experimental measurement is often too expensive. Predictive methods can replace measurements if they provide sufficiently good estimations. The estimated properties cannot be as precise as well-made measurements, but for many purposes the quality of estimated properties is sufficient. Predictive methods can also be used to check the results of experimental work. Principles A group-contribution method uses the principle that some simple aspects of the structures of chemical components are always the same in many different molecules ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chemistry
Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to the chemical compound, compounds made of atoms, molecules and ions: their composition, structure, properties, behavior and the changes they undergo during a Chemical reaction, reaction with other Chemical substance, substances. Chemistry also addresses the nature of chemical bonds in chemical compounds. 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 research, basic and Applied science, applied scientific disciplines at a fundamental level. For example, chemistry explains aspects of plant growth (botany), the formation of igneous rocks (geology), how atmospheric ozone is formed and how environmental pollutants are degraded (ecology), the properties ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Functional Group
In organic chemistry, a functional group is a substituent or moiety in a molecule that causes the molecule's characteristic chemical reactions. The same functional group will undergo the same or similar chemical reactions regardless of the rest of the molecule's composition. This enables systematic prediction of chemical reactions and behavior of chemical compounds and the design of chemical synthesis. The reactivity of a functional group can be modified by other functional groups nearby. Functional group interconversion can be used in retrosynthetic analysis to plan organic synthesis. A functional group is a group of atoms in a molecule with distinctive chemical properties, regardless of the other atoms in the molecule. The atoms in a functional group are linked to each other and to the rest of the molecule by covalent bonds. For repeating units of polymers, functional groups attach to their nonpolar core of carbon atoms and thus add chemical character to carbon chains. Fun ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Benson Group Increment Theory
Benson may refer to: Animals *Benson (fish), largest common carp caught in Britain Places Geography Canada *Rural Municipality of Benson No. 35, Saskatchewan; rural municipality *Benson, Saskatchewan; hamlet United Kingdom *Benson, Oxfordshire United States *Benson, Arizona **Benson (Amtrak station) in Benson, Arizona *Benson, Illinois *Benson, Louisiana *Benson, Maryland (other) * Benson, Michigan *Benson, Minnesota *Benson, New York *Benson, North Carolina *Benson, Pennsylvania *Benson, Utah * Benson, Vermont, a New England town ** Benson (CDP), Vermont, the main village in the town *Benson, Wisconsin *Benson County, North Dakota *Benson Lake, a lake in California * Benson neighborhood (Omaha, Nebraska) *Benson Township, Minnesota Education *Benson High School (other) *Benson Idahosa University, private Christian university in Benin City, Nigeria *Benson Polytechnic High School, public high school in Portland, Oregon * Florence C. Benson Elementary School, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
AIChE
The American Institute of Chemical Engineers (AIChE) is a professional organization for chemical engineers. AIChE was actually established in 1908 to distinguish chemical engineers as a profession independent of chemists and mechanical engineers. As of 2018, AIChE had over 60,000 members, including members from over 110 countries worldwide.About the AIChE, Overview (from the AIChE website) Student chapters at various universities around the world have also been established throughout its history. The student chapters tend to focus on providing networking opportunities in both academia and in industry as well as increasing student involvement locally and nationally. History of formation :''This section consists of excerpts from a historical pamphlet written for the Silver Anniversary of the AICHE in 1932.'' In 1905, ...[...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Beilstein Database
The Beilstein database is the largest database in the field of organic chemistry, in which compounds are uniquely identified by their Beilstein Registry Number. The database covers the scientific literature from 1771 to the present and contains experimentally validated information on millions of chemical reactions and substances from original scientific publications. The electronic database was created from ''Handbuch der Organischen Chemie'' (''Beilstein's Handbook of Organic Chemistry''), founded by Friedrich Konrad Beilstein in 1881, but has appeared online under a number of different names, including Crossfire Beilstein. Since 2009, the content has been maintained and distributed by Elsevier Information Systems in Frankfurt under the product name "Reaxys". The database contains information on reactions, substances, structures and properties. Up to 350 fields containing chemical and physical data (such as melting point, refractive index etc.) are available for each substance. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dortmund Data Bank
The Dortmund Data Bank (short DDB) is a factual data bank for thermodynamic and thermophysical data. Its main usage is the data supply for process simulation where experimental data are the basis for the design, analysis, synthesis, and optimization of chemical processes. The DDB is used for fitting parameters for thermodynamic models like NRTL or UNIQUAC and for many different equations describing pure component properties, e.g., the Antoine equation for vapor pressures. The DDB is also used for the development and revision of predictive methods like UNIFAC and PSRK. Contents Mixture properties * Phase equilibria data ( vapor–liquid, liquid–liquid, solid–liquid), data on azeotropy and zeotropy * Mixing enthalpies * Gas solubilities * Activity coefficients at infinite dilution * Heat capacities and excess heat capacities * Volumes, densities, and excess volumes (volume effect of mixing) * Salt solubilities * Octanol-water partition coefficients * Critical data T ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Standard Gibbs Free Energy Of Formation
The standard Gibbs free energy of formation (''G''f°) of a compound is the change of Gibbs free energy that accompanies the formation of 1 mole of a substance in its standard state from its constituent elements in their standard states (the most stable form of the element at 1 bar of pressure and the specified temperature, usually 298.15 K or 25 °C). The table below lists the standard Gibbs function of formation for several elements and chemical compounds and is taken from Lange's Handbook of Chemistry. Note that all values are in kJ/mol. Far more extensive tables can be found in the CRC Handbook of Chemistry and Physics and the NIST JANAF tables.M. W. Chase, NIST – JANAF Thermochemical Tables, 4th Edition, Journal of Physical and Chemical Reference Data, Monograph 9, 1998. The NIST Chemistry WebBook (see link below) is an online resource that contains standard enthalpy of formation for various compounds along with the standard absolute entropy for these compounds ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Additive Model
In statistics, an additive model (AM) is a nonparametric regression method. It was suggested by Jerome H. Friedman and Werner Stuetzle (1981) and is an essential part of the ACE algorithm. The ''AM'' uses a one-dimensional smoother to build a restricted class of nonparametric regression models. Because of this, it is less affected by the curse of dimensionality than e.g. a ''p''-dimensional smoother. Furthermore, the ''AM'' is more flexible than a standard linear model, while being more interpretable than a general regression surface at the cost of approximation errors. Problems with ''AM'', like many other machine learning methods, include model selection, overfitting, and multicollinearity. Description Given a data set \_^n of ''n'' statistical units, where \_^n represent predictors and y_i is the outcome, the ''additive model'' takes the form : \mathrm x_, \ldots, x_= \beta_0+\sum_^p f_j(x_) or : Y= \beta_0+\sum_^p f_j(X_)+\varepsilon Where \mathrm \epsilon = 0, \mathrm(\eps ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
UNIFAC
In statistical thermodynamics, the UNIFAC method ( UNIQUAC Functional-group Activity Coefficients)Aage Fredenslund, Russell L. Jones and John M. Prausnitz, "Group-Contribution Estimation of Activity Coefficients in Nonideal Liquid Mixtures", ''AIChE Journal'', vol. 21 (1975), p. 1086 is a semi-empirical system for the prediction of non-electrolyte activity in non-ideal mixtures. UNIFAC uses the functional groups present on the molecules that make up the liquid mixture to calculate activity coefficients. By using interactions for each of the functional groups present on the molecules, as well as some binary interaction coefficients, the activity of each of the solutions can be calculated. This information can be used to obtain information on liquid equilibria, which is useful in many thermodynamic calculations, such as chemical reactor design, and distillation calculations. The UNIFAC model was first published in 1975 by Fredenslund, Jones and John Prausnitz, a group of chemical ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Guldberg Rule
Cato Maximilian Guldberg (11 August 1836 – 14 January 1902) was a Norwegian mathematician and chemist. Guldberg is best known as a pioneer in physical chemistry. Background Guldberg was born in Christiania (now Oslo), Norway. He was the eldest son of Carl August Guldberg (1812–92) and Hanna Sophie Theresia Bull (1810–54). He was the brother of nurse and educator Cathinka Guldberg as well as mathematician Axel Sophus Guldberg. He attended Aug. Holths private latinskole in Christiania. Guldberg studied mathematics and physics at the University of Christiania and took his diploma in 1859. That same year he received the Crown Prince's gold medal (''Kronprinsens gullmedalje'') for a dissertation in pure mathematics. He received a travel and education scholarship in 1861, studying applied mathematics and machine learning in (Germany), Switzerland and France. Career Guldberg first taught at Hartvig Nissens skole in Christiania. Gulberg worked at the Royal Frederick Universi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Critical Temperature
Critical or Critically may refer to: *Critical, or critical but stable, medical states **Critical, or intensive care medicine *Critical juncture, a discontinuous change studied in the social sciences. *Critical Software, a company specializing in mission and business critical information systems *Critical theory, a school of thought that critiques society and culture by applying knowledge from the social sciences and the humanities * Critically endangered, a risk status for wild species *Criticality (status), the condition of sustaining a nuclear chain reaction Art, entertainment, and media * ''Critical'' (novel), a medical thriller written by Robin Cook * ''Critical'' (TV series), a Sky 1 TV series * "Critical" (''Person of Interest''), an episode of the American television drama series ''Person of Interest'' *"Critical", a 1999 single by Zion I People *Cr1TiKaL (born 1994), an American YouTuber and Twitch streamer See also *Critic *Criticality (other) *Critical Conditi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Joback Method
The Joback method (often named Joback/Reid method) predicts eleven important and commonly used pure component thermodynamic properties from molecular structure only. Basic principles Group-contribution method The Joback method is a group-contribution method. These kinds of methods use basic structural information of a chemical molecule, like a list of simple functional groups, add parameters to these functional groups, and calculate thermophysical and transport properties as a function of the sum of group parameters. Joback assumes that there are no interactions between the groups, and therefore only uses additive contributions and no contributions for interactions between groups. Other group-contribution methods, especially methods like UNIFAC, which estimate mixture properties like activity coefficients, use both simple additive group parameters and group-interaction parameters. The big advantage of using only simple group parameters is the small number of needed param ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
