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Pitzer Strain
In chemistry, a molecule experiences strain when its chemical structure undergoes some stress which raises its internal energy in comparison to a strain-free reference compound. The internal energy of a molecule consists of all the energy stored within it. A strained molecule has an additional amount of internal energy which an unstrained molecule does not. This extra internal energy, or strain energy, can be likened to a compressed spring.[1] Much like a compressed spring must be held in place to prevent release of its potential energy, a molecule can be held in an energetically unfavorable conformation by the bonds within that molecule
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Chemistry
Chemistry
Chemistry
is the scientific discipline involved with compounds composed of atoms, i.e. elements, and molecules, i.e. combinations of atoms: their composition, structure, properties, behavior and the changes they undergo during a reaction with other compounds.[1][2] Chemistry
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(s); ionic bonds, in which a compound donates one or more electrons to another compound to produce ions: cations and anions; hydrogen bonds; and Van der Waals force
Van der Waals force
bonds
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Pentane Interference
Pentane interference
Pentane interference
or syn-pentane interaction is the steric hindrance that the two terminal methyl groups experience in one of the chemical conformations of n-pentane. The possible conformations are combinations of anti conformations and gauche conformations and are anti-anti, anti-gauche+, gauche+ - gauche+ and gauche+ - gauche− of which the last one is especially energetically unfavorable. In macromolecules such as polyethylene pentane interference occurs between every fifth carbon atom. This is not to be confused with the 1,3-diaxial interactions of cyclohexane derivatives (gauche interactions shared between substituents and the ring). A clear example of the syn-pentane interaction is apparent in the diaxial versus diequatorial heats of formation of cis 1,3-dialkyl cyclohexanes
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Heat Of Combustion
The heating value (or energy value or calorific value) of a substance, usually a fuel or food (see food energy), is the amount of heat released during the combustion of a specified amount of it. The calorific value is the total energy released as heat when a substance undergoes complete combustion with oxygen under standard conditions. The chemical reaction is typically a hydrocarbon or other organic molecule reacting with oxygen to form carbon dioxide and water and release heat. It may be expressed with the quantities:energy/mole of fuel energy/mass of fuel energy/volume of the fuelThe calorific value is conventionally measured with a bomb calorimeter. It may also be calculated as the difference between the heat of formation ΔHo f of the products and reactants (though this approach is purely empirical since most heats of formation are calculated from measured heats of combustion)
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Methylcyclohexane
49.3 hPa at 20.0 °C 110.9 hPa at 37.7 °C[2]Magnetic susceptibility (χ)-78.91·10−6 cm3/molHazardsMain hazards severe fire hazardSafety data sheet [2]GHS pictogramsGHS signal word DangerGHS hazard statementsH225, H304, H315, H336, H410[2]GHS precautionary statementsP210, P235, P301+310, P331, P370+378, P403[2]NFPA 7043 1 0Flash point −4 °C (25 °F; 269 K)[2] Closed cupAutoignition temperature283 °C (541 °F; 556 K)[2]Explosive limits 1.2%-6.7%[1][2]Lethal dose or concentration (LD, LC):LD50 (median dose)2250 mg/kg (mouse, oral)[3]LC50 (median concentration)10172 ppm (mouse, 2 hr) 10,000-12,500 ppm (mouse, 2 hr) 15227 ppm (rabbit, 1 hr)[3]US health exposure limits (NIOSH):PEL (Permissible)TWA 500 ppm (2000 mg/m3)[1]REL (Recommended)TWA 400 ppm (1600 mg/m3)[1]<
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Benson Group Increment Theory
Benson Group Increment Theory (BGIT) or 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 the late Professor Sidney William Benson[1] of the University of Southern California. It is further described in a separate Wiki page. Heats of formations are intimately related to bond dissociation energies and thus are important in understanding chemical structure and reactivity.[2] Furthermore, although the theory is old, it still is practically useful as one of the best group additivity methods aside from computational methods such as molecular mechanics
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Van Der Waals Strain
In chemistry, van der Waals strain is strain resulting from van der Waals repulsion when two substituents in a molecule approach each other with a distance less than the sum of their van der Waals radii. Van der Waals strain is also called van der Waals repulsion and is related to steric hindrance.[1] One of the most common forms of this strain is eclipsing hydrogen, in Alkanes. In rotational and pseudorotational mechanisms[edit] In molecules whose vibrational mode involves a rotational or pseudorotational mechanism (such as the Berry mechanism or the Bartell mechanism),[2] van der Waals strain can cause significant differences in potential energy, even between molecules with identical geometry. PF5, for example, has significantly lower potential energy than PCl5. Despite their identical trigonal bipyramidal molecular geometry, the higher electron count of chlorine as compared to fluorine causes a potential energy spike as the molecule enters its intermediate in the mechanism and the s
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Van Der Waals Radius
The van der Waals radius, rw, of an atom is the radius of an imaginary hard sphere representing the distance of closest approach for another atom. It is named after Johannes Diderik van der Waals, winner of the 1910 Nobel Prize in Physics, as he was the first to recognise that atoms were not simply points and to demonstrate the physical consequences of their size through the van der Waals equation of state.Contents1 Van der Waals volume 2 Methods of determination2.1 Van der Waals equation
Van der Waals equation
of state 2.2 Crystallographic measurements 2.3 Molar refractivity 2.4 Polarizability3 References3.1 Further reading4 External linksVan der Waals volume[edit]This section does not cite any sources. Please help improve this section by adding citations to reliable sources. Unsourced material may be challenged and removed
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Butyl
In organic chemistry, butyl is a four-carbon alkyl radical or substituent group with general chemical formula −C4H9, derived from either of the two isomers of butane. The isomer n-butane can connect in two ways, giving rise to two "-butyl" groups:If it connects at one of the two terminal carbon atoms, it is normal butyl or n-butyl: CH3−CH2−CH2−CH2− (fully systematic name: butyl) If it connects at one of the non-terminal (internal) carbon atoms, it is secondary butyl or sec-butyl: CH3−CH2−CH(CH3)− (fully systematic name: 1-methylpropyl)The second isomer of butane, isobutane, can also connect in two ways, giving rise to two additional groups:If it connects at one of the three terminal carbons, it is isobutyl: (CH3)2CH−CH2− (fully systematic name: 2-methylpropyl) If it connects at the central carbon, it is tertiary butyl, tert-butyl or t-butyl: (CH3)3C− (fully systematic name: 1,1-dimethylethyl)Contents1 Nomenclature 2 Example 3 Ety
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Methyl Group
A methyl group is an alkyl derived from methane, containing one carbon atom bonded to three hydrogen atoms — CH3. In formulas, the group is often abbreviated Me. Such hydrocarbon groups occur in many organic compounds. It is a very stable group in most molecules. While the methyl group is usually part of a larger molecule, it can be found on its own in any of three forms: anion, cation or radical. The anion has eight valence electrons, the radical seven and the cation six. All three forms are highly reactive and rarely observed.[1]Contents1 Methyl cation, anion, and radical1.1 Methyl cation 1.2 Methyl anion 1.3 Methyl radical2 Reactivity2.1 Oxidation 2.2 Methylation 2.3 Deprotonation 2.4 Free radical reactions3 Chiral
Chiral
methyl 4 Etymology 5 See also 6 ReferencesMethyl cation, anion, and radical[edit] Methyl cation[edit] The methylium cation (CH3+) exists in the gas phase, but is otherwise not encountered
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Trimethylboron
Trimethylborane (TMB) is a toxic, pyrophoric gas with the formula B(CH3)3 (which can also be written as Me3B, with Me representing methyl).Contents1 Properties 2 Preparation 3 Reactions 4 Use 5 ReferencesProperties[edit] As a liquid it is colourless. The strongest line in the infrared spectrum is at 1330 cm−1 followed by lines at 3010 cm−1 and 1185 cm−1. Its melting point is −161.5 °C, and its boiling point is −20.2 °C. Vapour pressure is given by log P = 6.1385 + 1.75 log T − 1393.3/T − 0.007735 T, where T is temperature in kelvins.[5] Molecular weight is 55.914. The heat of vapourisation is 25.6 kJ/mol.[4] Preparation[edit] Trimethylborane was first made by Stock and Zeidler
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Herbert C. Brown
Herbert Charles Brown (May 22, 1912 – December 19, 2004) was an English-born American chemist and recipient of the 1979 Nobel Prize in Chemistry
Chemistry
for his work with organoboranes.Contents1 Life and career 2 Research 3 See also 4 References 5 External linksLife and career[edit] Brown was born Herbert Brovarnik in London, to Ukrainian Jewish immigrants from Zhitomir, Pearl (née Gorinstein) and Charles Brovarnik, a hardware store manager and carpenter.[2] He moved to Chicago
Chicago
in June 1914, at the age of two.[3][4] Brown attended Crane Junior College in Chicago, where he met Sarah Baylen, whom he would later marry. The college closed soon after, and Brown and Baylen transferred to Wright Junior College.[4] In 1935 he left Wright Junior College and that autumn entered the University of Chicago, completed two years of studies in three quarters, and earned a B.S
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Alkyl
In organic chemistry, an alkyl substituent is an alkane missing one hydrogen.[1] The term alkyl is intentionally unspecific to include many possible substitutions. An acyclic alkyl has the general formula CnH2n+1. A cycloalkyl is derived from a cycloalkane by removal of a hydrogen atom from a ring and has the general formula CnH2n-1.[2] Typically an alkyl is a part of a larger molecule. In structural formula, the symbol R is used to designate a generic (unspecified) alkyl group. The smallest alkyl group is methyl, with the formula CH3−. [3]Contents1 In everyday life 2 In medicinal chemistry 3 Alkyl
Alkyl
cations, anions, and radicals 4 Nomenclature 5 Etymology 6 See also 7 ReferencesIn everyday life[edit] The word root alkyl is encountered in several contexts. Alkylation
Alkylation
is an important operation in refineries, for example in the production of high-octane gasoline
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Pentane
Pentane
Pentane
is an organic compound with the formula C5H12—that is, an alkane with five carbon atoms. The term may refer to any of three structural isomers, or to a mixture of them: in the IUPAC nomenclature, however, pentane means exclusively the n-pentane isomer; the other two are called isopentane (methylbutane) and neopentane (dimethylpropane). Cyclopentane
Cyclopentane
is not an isomer of pentane because it has only 10 hydrogen atoms where pentane has 12. Pentanes are components of some fuels and are employed as specialty solvents in the laboratory. Their properties are very similar to those of butanes and hexanes.Contents1 Industrial uses 2 Laboratory
Laboratory
use 3 Physical properties 4 Reactions 5 References 6 External linksIndustrial uses[edit] Pentanes are some of the primary blowing agents used in the production of polystyrene foam and other foams
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Methylcyclopentane
Methylcyclopentane
Methylcyclopentane
is an organic compound with the chemical formula CH3C5H9. It is a colourless, flammable liquid with a faint odor. It is a component of the naphthene fraction of petroleum. It usually is obtained as a mixture with cyclohexane. It is mainly converted in naphthene reformers to benzene..[2] Methylcyclopentane
Methylcyclopentane
is not perfectly planar and can pucker to alleviate stress in its structure.[3] References[edit]^ a b c Lide, David. R, ed. (2009). CRC Handbook of Chemistry and Physics (89th ed.). CRC Press. ISBN 978-1-4200-6679-1.  ^ M. Larry Campbell. "Cyclohexane" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2012. doi:10.1002/14356007.a08_209.pub2 ^ Carey, Francis; Giuliano, Robert (2014). "3". Organic Chemistry (9 ed.). McGraw-Hill. pp. 97–131
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Cyclopentane
Cyclopentane
Cyclopentane
is a highly flammable alicyclic hydrocarbon with chemical formula C5H10
C5H10
and CAS number 287-92-3, consisting of a ring of five carbon atoms each bonded with two hydrogen atoms above and below the plane. It occurs as a colorless liquid with a petrol-like odor
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