Simplified molecular-input line-entry system
The simplified molecular-input line-entry system is a specification in the form of a line notation for describing the structure of chemical species using short ASCII strings. SMILES strings can be imported by most molecule editors for conversion back into two-dimensional drawings or three-dimensional models of the molecules; the original SMILES specification was initiated in the 1980s. It has since been extended. In 2007, an open standard called. Other linear notations include the Wiswesser line notation, ROSDAL, SYBYL Line Notation; the original SMILES specification was initiated by David Weininger at the USEPA Mid-Continent Ecology Division Laboratory in Duluth in the 1980s. Acknowledged for their parts in the early development were "Gilman Veith and Rose Russo and Albert Leo and Corwin Hansch for supporting the work, Arthur Weininger and Jeremy Scofield for assistance in programming the system." The Environmental Protection Agency funded the initial project to develop SMILES. It has since been modified and extended by others, most notably by Daylight Chemical Information Systems.
In 2007, an open standard called "OpenSMILES" was developed by the Blue Obelisk open-source chemistry community. Other'linear' notations include the Wiswesser Line Notation, ROSDAL and SLN. In July 2006, the IUPAC introduced the InChI as a standard for formula representation. SMILES is considered to have the advantage of being more human-readable than InChI; the term SMILES refers to a line notation for encoding molecular structures and specific instances should be called SMILES strings. However, the term SMILES is commonly used to refer to both a single SMILES string and a number of SMILES strings; the terms "canonical" and "isomeric" can lead to some confusion when applied to SMILES. The terms are not mutually exclusive. A number of valid SMILES strings can be written for a molecule. For example, CCO, OCC and CC all specify the structure of ethanol. Algorithms have been developed to generate the same SMILES string for a given molecule; this SMILES is unique for each structure, although dependent on the canonicalization algorithm used to generate it, is termed the canonical SMILES.
These algorithms first convert the SMILES to an internal representation of the molecular structure. Various algorithms for generating canonical SMILES have been developed and include those by Daylight Chemical Information Systems, OpenEye Scientific Software, MEDIT, Chemical Computing Group, MolSoft LLC, the Chemistry Development Kit. A common application of canonical SMILES is indexing and ensuring uniqueness of molecules in a database; the original paper that described the CANGEN algorithm claimed to generate unique SMILES strings for graphs representing molecules, but the algorithm fails for a number of simple cases and cannot be considered a correct method for representing a graph canonically. There is no systematic comparison across commercial software to test if such flaws exist in those packages. SMILES notation allows the specification of configuration at tetrahedral centers, double bond geometry; these are structural features that cannot be specified by connectivity alone and SMILES which encode this information are termed isomeric SMILES.
A notable feature of these rules is. The term isomeric SMILES is applied to SMILES in which isotopes are specified. In terms of a graph-based computational procedure, SMILES is a string obtained by printing the symbol nodes encountered in a depth-first tree traversal of a chemical graph; the chemical graph is first trimmed to remove hydrogen atoms and cycles are broken to turn it into a spanning tree. Where cycles have been broken, numeric suffix labels are included to indicate the connected nodes. Parentheses are used to indicate points of branching on the tree; the resultant SMILES form depends on the choices: of the bonds chosen to break cycles, of the starting atom used for the depth-first traversal, of the order in which branches are listed when encountered. Atoms are represented by the standard abbreviation of the chemical elements, in square brackets, such as for gold. Brackets may be omitted in the common case of atoms which: are in the "organic subset" of B, C, N, O, P, S, F, Cl, Br, or I, have no formal charge, have the number of hydrogens attached implied by the SMILES valence model, are the normal isotopes, are not chiral centers.
All other elements must be enclosed in brackets, have charges and hydrogens shown explicitly. For instance, the SMILES for water may be written as either O or. Hydrogen may be written as a separate atom; when brackets are used, the symbol H is added if the atom in brackets is bonded to one or more hydrogen, followed by the number of hydrogen atoms if greater than 1 by the sign + for a positive charge or by - for a negative charge. For example, for ammonium. If there is more than one charge, it is written as digit.
Pyrolysis is the thermal decomposition of materials at elevated temperatures in an inert atmosphere. It is irreversible; the word is coined from the Greek-derived elements pyro "fire" and lysis "separating". Pyrolysis is most used in the treatment of organic materials, it is one of the processes involved in charring wood. In general, pyrolysis of organic substances produces volatile products and leaves a solid residue enriched in carbon, char. Extreme pyrolysis, which leaves carbon as the residue, is called carbonization; the process is used in the chemical industry, for example, to produce ethylene, many forms of carbon, other chemicals from petroleum and wood, to produce coke from coal. Aspirational applications of pyrolysis would convert biomass into syngas and biochar, waste plastics back into usable oil, or waste into safely disposable substances. Pyrolysis is one of various types of chemical degradation processes that occur at higher temperatures, it differs from other processes like combustion and hydrolysis in that it does not involve the addition of other reagents such as oxygen or water.
Complete pyrolysis of organic matter leaves a solid residue that consists of elemental carbon. More specific cases of pyrolysis include dry distillation, as in the original production of sulfuric acid from sulfates destructive distillation, as in the manufacture of charcoal and activated carbon caramelization of sugars high-temperature cooking processes such as roasting, frying and grilling cracking of heavier hydrocarbons into lighter ones, as in oil refining thermal depolymerization, that breaks down plastics and other polymers into monomers and oligomers hydrous pyrolysis, in the presence of superheated water or steam used in oil refining catagenesis, the natural conversion of buried organic matter to fossil fuels flash vacuum pyrolysis, used in organic synthesis Pyrolysis consists in heating the material above its decomposition temperature, breaking chemical bonds in its molecules; the fragments become smaller molecules, but may combine to produce residues with larger molecular mass amorphous covalent solids.
In many settings, some amounts of oxygen, water, or other substances may be present, so that combustion, hydrolysis, or other chemical processes may occur besides pyrolysis proper. Sometimes those chemical are added intentionally, as in the burning of firewood, in the traditional manufacture of charcoal, in the steam cracking of crude oil. Conversely, the starting material may be heated in a vacuum or in an inert atmosphere avoid adverse chemical reactions. Pyrolysis in a vacuum lowers the boiling point of the byproducts, improving their recovery; when organic matter is heated at increasing temperatures in open containers, the following processes occur, in successive or overlapping stages: Below about 100 °C, including some water, evaporate. Heat-sensitive substances, such as vitamin C and proteins, may change or decompose at this stage. At about 100 °C or higher, any remaining water, absorbed in the material is driven off. Water trapped in crystal structure of hydrates may come off at somewhat higher temperatures.
This process consumes a lot of energy, so the temperature may stop rising until this stage is complete. Some solid substances, like fats and sugars, may melt and separate. Between 100 and 500 °C, many common organic molecules break down. Most sugars start decomposing at 160-180 °C. Cellulose, a major component of wood and cotton fabrics, decomposes at about 350 °C. Lignin, another major wood component, starts decomposing at about 350 °C, but continues releasing volatile products up to 500 °C; the decomposition products include water, carbon monoxide CO and/or carbon dioxide CO2, as well as a large number of organic compounds. Gases and volatile products leave the sample, some of them may condense again as smoke; this process absorbs energy. Some volatiles may burn, creating a visible flame; the non-volatile residues become richer in carbon and form large disordered molecules, with colors ranging between brown and black. At this point the matter is said to have been "charred" or "carbonized". At 200-300 °C, if oxygen has not been excluded, the carbonaceous residue may start to burn, in a exothermic reaction with no or little visible flame.
Once carbon combustion starts, the temperature rises spontaneously, turning the residue into a glowing ember and releasing carbon dioxide and/or monoxide. At this stage, some of the nitrogen still remaining in the residue may be oxidized into nitrogen oxides like NO2 and N2O3. Sulfur and other elements like chlorine and arsenic may be volatilized at this stage. Once combustion of the carbonaceous residue is complete, a powdery or solid mineral residue is left behind, consisting of inorganic oxidized materials of high melting point; some of the ash may have left during combustion, entrained by the gases as fly ash or particulate emissions. Metals present in the original matter remain in the ash as oxides or carbonates, such as potash. Phosphorus, from materials such as bone and nucleic acids remains as phosphates. Pyrolysis is used to produce ethylene, the chemical compound produced on the largest scale industrially. In this process, hydrocarbons from petroleum are heated to around 600 °C in the presence of steam.
The resulting ethylene is used to make antifreeze (e
Printed circuit board
A printed circuit board mechanically supports and electrically connects electronic components or electrical components using conductive tracks and other features etched from one or more sheet layers of copper laminated onto and/or between sheet layers of a non-conductive substrate. Components are soldered onto the PCB to both electrically connect and mechanically fasten them to it. Printed circuit boards are used in all but the simplest electronic products, they are used in some electrical products, such as passive switch boxes. Alternatives to PCBs include wire wrap and point-to-point construction, both once popular but now used. PCBs require additional design effort to lay out the circuit, but manufacturing and assembly can be automated. Specialized CAD software is available to do much of the work of layout. Mass-producing circuits with PCBs is cheaper and faster than with other wiring methods, as components are mounted and wired in one operation. Large numbers of PCBs can be fabricated at the same time, the layout only has to be done once.
PCBs can be made manually in small quantities, with reduced benefits. PCBs can be double-sided, or multi-layer. Multi-layer PCBs allow for much higher component density, because circuit traces on the inner layers would otherwise take up surface space between components; the rise in popularity of multilayer PCBs with more than two, with more than four, copper planes was concurrent with the adoption of surface mount technology. However, multilayer PCBs make repair and field modification of circuits much more difficult and impractical; the world market for bare PCBs exceeded $60.2 billion in 2014. In 2018, the Global Single Sided Printed Circuit Board Market Analysis Report estimated that the PCB market would reach $79 billion by 2024. Before the development of printed circuit boards electrical and electronic circuits were wired point-to-point on a chassis; the chassis was a sheet metal frame or pan, sometimes with a wooden bottom. Components were attached to the chassis by insulators when the connecting point on the chassis was metal, their leads were connected directly or with jumper wires by soldering, or sometimes using crimp connectors, wire connector lugs on screw terminals, or other methods.
Circuits were large, bulky and fragile, production was labor-intensive, so the products were expensive. Development of the methods used in modern printed circuit boards started early in the 20th century. In 1903, a German inventor, Albert Hanson, described flat foil conductors laminated to an insulating board, in multiple layers. Thomas Edison experimented with chemical methods of plating conductors onto linen paper in 1904. Arthur Berry in 1913 patented a print-and-etch method in the UK, in the United States Max Schoop obtained a patent to flame-spray metal onto a board through a patterned mask. Charles Ducas in 1927 patented a method of electroplating circuit patterns; the Austrian engineer Paul Eisler invented the printed circuit as part of a radio set while working in the UK around 1936. In 1941 a multi-layer printed circuit was used in German magnetic influence naval mines. Around 1943 the USA began to use the technology on a large scale to make proximity fuses for use in World War II. After the war, in 1948, the USA released the invention for commercial use.
Printed circuits did not become commonplace in consumer electronics until the mid-1950s, after the Auto-Sembly process was developed by the United States Army. At around the same time in the UK work along similar lines was carried out by Geoffrey Dummer at the RRDE; as circuit boards became available, the point-to-point chassis construction method remained in common use in industry into at least the late 1960s. Printed circuit boards were introduced to reduce the size and cost of parts of the circuitry. In 1960, a small consumer radio receiver might be built with all its circuitry on one circuit board, but a TV set would contain one or more circuit boards. Predating the printed circuit invention, similar in spirit, was John Sargrove's 1936–1947 Electronic Circuit Making Equipment which sprayed metal onto a Bakelite plastic board; the ECME could produce three radio boards per minute. During World War II, the development of the anti-aircraft proximity fuse required an electronic circuit that could withstand being fired from a gun, could be produced in quantity.
The Centralab Division of Globe Union submitted a proposal which met the requirements: a ceramic plate would be screenprinted with metallic paint for conductors and carbon material for resistors, with ceramic disc capacitors and subminiature vacuum tubes soldered in place. The technique proved viable, the resulting patent on the process, classified by the U. S. Army, was assigned to Globe Union, it was not until 1984 that the Institute of Electrical and Electronics Engineers awarded Harry W. Rubinstein the Cledo Brunetti Award for early key contributions to the development of printed components and conductors on a common insulating substrate. Rubinstein was honored in 1984 by his alma mater, the University of Wisconsin-Madison, for his innovations in the technology of printed electronic circuits and the fabrication of capacitors; this invention represents a step in the development of integrated circuit technology, as not only wiring but passive components were fabricated on the ceramic substrate.
Every electronic component had
In organic chemistry, the Diels–Alder reaction is a chemical reaction between a conjugated diene and a substituted alkene termed the dienophile, to form a substituted cyclohexene derivative. It is the prototypical example of a pericyclic reaction with a concerted mechanism. More it is classified as a thermally-allowed cycloaddition with Woodward–Hoffmann symbol, it was first described by Otto Diels and Kurt Alder in 1928. For the discovery of this reaction, they were awarded the Nobel Prize in Chemistry in 1950. Through the simultaneous construction of two new carbon–carbon bonds, the Diels–Alder reaction provides a reliable way to form six-membered rings with good control over the regio- and stereochemical outcomes, it has served as a powerful and applied tool for the introduction of chemical complexity in the synthesis of natural products and new materials. The underlying concept has been applied to π-systems involving heteroatoms, such as carbonyls and imines, which furnish the corresponding heterocycles.
The reaction has been generalized to other ring sizes, although none of these generalizations have matched the formation of six-membered rings in terms of scope or versatility. Because of the negative values of ΔH° and ΔS° for a typical Diels–Alder reaction, the microscopic reverse of a Diels–Alder reactions becomes favorable at high temperatures, although this is of synthetic importance for only a limited range of Diels-Alder adducts with some special structural features; the reaction is an example of a concerted pericyclic reaction. It is believed to occur via a single, cyclic transition state, with no intermediates generated during the course of the reaction; as such, the Diels–Alder reaction is governed by orbital symmetry considerations: it is classified as a cycloaddition, indicating that it proceeds through the suprafacial/suprafacial interaction of a 4π electron system with a 2π electron system, an interaction that leads to a transition state without an additional orbital symmetry-imposed energetic barrier and allows the Diels-Alder reaction to take place with relative ease.
A consideration of the reactants' frontier molecular orbitals makes plain. For the more common "normal" electron demand Diels–Alder reaction, the more important of the two HOMO/LUMO interactions is that between the electron-rich diene's ψ2 as the highest occupied molecular orbital with the electron-deficient dienophile's π* as the lowest unoccupied molecular orbital. However, the HOMO–LUMO energy gap is close enough that the roles can be reversed by switching electronic effects of the substituents on the two components. In an inverse electron-demand Diels–Alder reaction, electron-withdrawing substituents on the diene lower the energy of its empty ψ3 orbital and electron-donating substituents on the dienophile raise the energy of its filled π orbital sufficiently that the interaction between these two orbitals becomes the most energetically significant stabilizing orbital interaction. Regardless of which situation pertains, the HOMO and LUMO of the components are in phase and a bonding interaction results as can be seen in the diagram below.
Since the reactants are in their ground state, the reaction is initiated thermally and does not require activation by light. The "prevailing opinion" is that most Diels–Alder reactions proceed through a concerted mechanism. Despite the fact that the vast majority of Diels–Alder reactions exhibit stereospecific, syn addition of the two components, a diradical intermediate has been postulated on the grounds that the observed stereospecificity does not rule out a two-step addition involving an intermediate that collapses to product faster than it can rotate to allow for inversion of stereochemistry. There is a notable rate enhancement when certain Diels–Alder reactions are carried out in polar organic solvents such as dimethylformamide and ethylene glycol. and in water. The reaction of cyclopentadiene and butenone for example is 700 times faster in water relative to 2,2,4-trimethylpentane as solvent. Several explanations for this effect have been proposed, such as an increase in effective concentration due to hydrophobic packing or hydrogen-bond stabilization of the transition state.
The geometry of the diene and dienophile components each propagate into stereochemical details of the product. For intermolecular reactions the preferred positional and stereochemical relationship of subtituents of the two components compared to each other are controlled by electronic effects. However, for intramolecular Diels–Alder cycloaddition reactions, the conformational stability of the structure the transition state can be an overwhelming influence. Frontier molecular orbital theory has been used to explain the regioselectivity patterns observed in Diels–Alder reactions of substituted systems. Calculation of the energy and orbital coefficients of the components' frontier orbitals provides a picture, in good accord with the more straightforward analysis of the substituents' resonance effects, as illustrated below. In general, the regioselectivity found for both normal and inverse electron-demand Diels–Alder reaction follows the ortho-para rule, so named, because the cyclohexene product bears substituents in positions that are analogous to the ortho and para positions of disubstituted arenes.
For example, in a normal-demand scenario
A polymer is a large molecule, or macromolecule, composed of many repeated subunits. Due to their broad range of properties, both synthetic and natural polymers play essential and ubiquitous roles in everyday life. Polymers range from familiar synthetic plastics such as polystyrene to natural biopolymers such as DNA and proteins that are fundamental to biological structure and function. Polymers, both natural and synthetic, are created via polymerization of many small molecules, known as monomers, their large molecular mass relative to small molecule compounds produces unique physical properties, including toughness, a tendency to form glasses and semicrystalline structures rather than crystals. The terms polymer and resin are synonymous with plastic; the term "polymer" derives from the Greek word πολύς and μέρος, refers to a molecule whose structure is composed of multiple repeating units, from which originates a characteristic of high relative molecular mass and attendant properties. The units composing polymers derive or conceptually, from molecules of low relative molecular mass.
The term was coined in 1833 by Jöns Jacob Berzelius, though with a definition distinct from the modern IUPAC definition. The modern concept of polymers as covalently bonded macromolecular structures was proposed in 1920 by Hermann Staudinger, who spent the next decade finding experimental evidence for this hypothesis. Polymers are studied in the fields of biophysics and macromolecular science, polymer science. Products arising from the linkage of repeating units by covalent chemical bonds have been the primary focus of polymer science. Polyisoprene of latex rubber is an example of a natural/biological polymer, the polystyrene of styrofoam is an example of a synthetic polymer. In biological contexts all biological macromolecules—i.e. Proteins, nucleic acids, polysaccharides—are purely polymeric, or are composed in large part of polymeric components—e.g. Isoprenylated/lipid-modified glycoproteins, where small lipidic molecules and oligosaccharide modifications occur on the polyamide backbone of the protein.
The simplest theoretical models for polymers are ideal chains. Polymers are of two types: occurring and synthetic or man made. Natural polymeric materials such as hemp, amber, wool and natural rubber have been used for centuries. A variety of other natural polymers exist, such as cellulose, the main constituent of wood and paper; the list of synthetic polymers in order of worldwide demand, includes polyethylene, polystyrene, polyvinyl chloride, synthetic rubber, phenol formaldehyde resin, nylon, polyacrylonitrile, PVB, many more. More than 330 million tons of these polymers are made every year. Most the continuously linked backbone of a polymer used for the preparation of plastics consists of carbon atoms. A simple example is polyethylene. Many other structures do exist. Oxygen is commonly present in polymer backbones, such as those of polyethylene glycol, DNA. Polymerization is the process of combining many small molecules known as monomers into a covalently bonded chain or network. During the polymerization process, some chemical groups may be lost from each monomer.
This happens in the polymerization of PET polyester. The monomers are terephthalic acid and ethylene glycol but the repeating unit is —OC—C6H4—COO—CH2—CH2—O—, which corresponds to the combination of the two monomers with the loss of two water molecules; the distinct piece of each monomer, incorporated into the polymer is known as a repeat unit or monomer residue. Laboratory synthetic methods are divided into two categories, step-growth polymerization and chain-growth polymerization; the essential difference between the two is that in chain growth polymerization, monomers are added to the chain one at a time only, such as in polyethylene, whereas in step-growth polymerization chains of monomers may combine with one another directly, such as in polyester. Newer methods, such as plasma polymerization do not fit neatly into either category. Synthetic polymerization reactions may be carried out without a catalyst. Laboratory synthesis of biopolymers of proteins, is an area of intensive research. There are three main classes of biopolymers: polysaccharides and polynucleotides.
In living cells, they may be synthesized by enzyme-mediated processes, such as the formation of DNA catalyzed by DNA polymerase. The synthesis of proteins involves multiple enzyme-mediated processes to transcribe genetic information from the DNA to RNA and subsequently translate that information to synthesize the specified protein from amino acids; the protein may be modified further following translation in order to provide appropriate structure and functioning. There are other biopolymers such as rubber, suberin and lignin. Occurring polymers such as cotton and rubber were familiar materials for years before synthetic polymers such as polyethene and perspex appeared on the market. Many commercially important polymers are synthesized by chemical modification of occurring polymers. Prominent examples inclu
Epoxy is either any of the basic components or the cured end products of epoxy resins, as well as a colloquial name for the epoxide functional group. Epoxy resins known as polyepoxides, are a class of reactive prepolymers and polymers which contain epoxide groups. Epoxy resins may be reacted either with themselves through catalytic homopolymerisation, or with a wide range of co-reactants including polyfunctional amines, phenols and thiols; these co-reactants are referred to as hardeners or curatives, the cross-linking reaction is referred to as curing. Reaction of polyepoxides with themselves or with polyfunctional hardeners forms a thermosetting polymer with favorable mechanical properties and high thermal and chemical resistance. Epoxy has a wide range of applications, including metal coatings, use in electronics/electrical components/LEDs, high tension electrical insulators, paint brush manufacturing, fiber-reinforced plastic materials and structural adhesives. Epoxy is sometimes used as a glue.
Epoxy resins are low molecular weight pre-polymers or higher molecular weight polymers which contain at least two epoxide groups. The epoxide group is sometimes referred to as a glycidyl or oxirane group. A wide range of epoxy resins are produced industrially; the raw materials for epoxy resin production are today petroleum derived, although some plant derived sources are now becoming commercially available. Epoxy resins are polymeric or semi-polymeric materials or an oligomer, as such exist as pure substances, since variable chain length results from the polymerisation reaction used to produce them. High purity grades can be produced for certain applications, e.g. using a distillation purification process. One downside of high purity liquid grades is their tendency to form crystalline solids due to their regular structure, which require melting to enable processing. An important criterion for epoxy resins is the epoxide group content; this is expressed as the specific amount of substance of epoxide groups in the material B under consideration, calculated as the ratio of the amount of substance of epoxide groups in this material B, n, divided by the mass m of the material B under consideration, in this case, the mass of the resin.
The SI unit for this quantity multiples thereof. Several deprecated quantities are still in use, including the so-called "epoxide number", not a number and should therefore not be referred to as such, but instead is the ratio of the amount of substance of epoxide groups, n, the mass m of the material B, with the SI unit "mol/kg"; the inverse of the epoxide number is called the "epoxide equivalent weight", the ratio of the mass of a sample B of the resin and the amount of substance of epoxide groups present in that sample B, with the SI unit "kg/mol", is a deprecated quantity. The specific amount of substance of epoxide groups is used to calculate the mass of co-reactant to use when curing epoxy resins. Epoxies are cured with stoichiometric or near-stoichiometric quantities of curative to achieve maximum physical properties; as with other classes of thermoset polymer materials, blending different grades of epoxy resin, as well as use of additives, plasticizers or fillers is common to achieve the desired processing or final properties, or to reduce cost.
Use of blending and fillers is referred to as formulating. Important epoxy resins are produced from combining epichlorohydrin and bisphenol A to give bisphenol A diglycidyl ethers. Increasing the ratio of bisphenol A to epichlorohydrin during manufacture produces higher molecular weight linear polyethers with glycidyl end groups, which are semi-solid to hard crystalline materials at room temperature depending on the molecular weight achieved; this route of synthesis is known as the "taffy" process. More modern manufacturing methods of higher molecular weight epoxy resins is to start with liquid epoxy resin and add a calculated amount of bisphenol A and a catalyst is added and the reaction heated to circa 160 °C; this process is known as "advancement". There are numerous patents and articles on this process, popular for over 20 years; as the molecular weight of the resin increases, the epoxide content reduces and the material behaves more and more like a thermoplastic. High molecular weight polycondensates form a class known as phenoxy resins and contain no epoxide groups.
These resins do however contain hydroxyl groups throughout the backbone, which may undergo other cross-linking reactions, e.g. with aminoplasts and isocyanates. Bisphenol F may undergo epoxy resin formation in a similar fashion to bisphenol A; these resins have lower viscosity and a higher mean epoxy content per gramme than bisphenol A resins, which gives them increased chemical resistance. Reaction of phenols with formaldehyde and subsequent glycidylation with epichlorohydrin produces epoxidised novolacs, such as epoxy phenol novolacs and epoxy cresol novolacs; these are viscous to solid resins with typical mean epoxide functionality of around 2 to 6. The high epoxide functionality of these resins forms a crosslinked polymer network displaying high temperature and chemical resistance, but low flexibility. A related class is cycloaliphatic epoxy resin, which contains one or more cycloaliphatic rings in the molecule (e.g. 3,4-epoxycyclohexylmethyl-3,4-epoxycyc
The Jmol applet, among other abilities, offers an alternative to the Chime plug-in, no longer under active development. While Jmol has many features that Chime lacks, it does not claim to reproduce all Chime functions, most notably, the Sculpt mode. Chime requires plug-in installation and Internet Explorer 6.0 or Firefox 2.0 on Microsoft Windows, or Netscape Communicator 4.8 on Mac OS 9. Jmol operates on a wide variety of platforms. For example, Jmol is functional in Mozilla Firefox, Internet Explorer, Google Chrome, Safari. Chemistry Development Kit Comparison of software for molecular mechanics modeling Jmol extension for MediaWiki List of molecular graphics systems Molecular graphics Molecule editor Proteopedia PyMOL SAMSON Official website Wiki with listings of websites and moodles Willighagen, Egon. "Fast and Scriptable Molecular Graphics in Web Browsers without Java3D". Doi:10.1038/npre.2007.50.1