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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 molecule ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chemistry
Chemistry is the scientific study of the properties and behavior of matter. It is a physical science within the natural sciences that studies the chemical elements that make up matter and chemical compound, compounds made of atoms, molecules and ions: their composition, structure, properties, behavior and the changes they undergo during chemical reaction, reactions 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 prop ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Functional Group
In organic chemistry, a functional group is any substituent or moiety (chemistry), 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 (chemistry), 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 property, 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 Chemical polarity, nonp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Benson Group Increment Theory
Benson group-increment theory (BGIT), group-increment theory, or Benson group additivity uses the experimentally calculated heat of formation for individual groups of atoms to calculate the entire heat of formation for a molecule under investigation. This can be a quick and convenient way to determine theoretical heats of formation without conducting tedious experiments. The technique was developed by professor Sidney William Benson of the University of Southern California. It is further described in Heat of formation group additivity. Heats of formations are intimately related to bond-dissociation energies and thus are important in understanding chemical structure and reactivity.Benson, S. W. ''Journal of Chemical Education'' 42, 502–518 (1965). Furthermore, although the theory is old, it still is practically useful as one of the best group-contribution methods aside from computational methods such as molecular mechanics. However, the BGIT has its limitations, and thus cannot ... [...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 established in 1908 to distinguish chemical engineers as professionals independent of chemists and mechanical engineers. Currently, AIChE has over 60,000 members from over 110 countriesAbout the AIChE, Overview (from the AIChE website) or 40,000 members from 93 countries. by 2024 (sources vary). There are over 350 active student chapters at universities worldwide. Student chapters aim to provide networking opportunities in academia and industry as well as increase 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.''[...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Beilstein Database
The Beilstein database is a 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. Referen ... [...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 * Criti ... [...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 molar entropy for these compounds fro ... [...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 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(\e ... [...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 on 11 August 1836, in Christiania. 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 what is now Germany, Switzerland and France. Career Guldberg first taught at Hartvig Nissens skole in Christiania. Gulberg worked at the Royal Frederick ... [...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), ''Critical'' (novel), a medical thriller written by Robin Cook *Critical (TV series), ''Critical'' (TV series), a Sky 1 TV series *Critical (Person of Interest), "Critical" (''Person of Interest''), an episode of the American television drama series ''Person of Interest'' *"Critical", a song by Abhi the Nomad from the album ''Abhi vs the Universe'', 2021 *"Critical", a 1999 sin ... [...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. It is named after Kevin G. Joback in 1984 and developed it further with Robert C. Reid. The Joback method is an extension of the Lydersen method and uses very similar groups, formulas, and parameters for the three properties the Lydersen already supported (critical temperature, critical pressure, critical volume). Joback and Reid extended the range of supported properties, created new parameters and modified slightly the formulas of the old Lydersen method. 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 paramete ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
