Hydrocarbons allenic

The second boundary condition assures total finite existence probability at any time the first boundary condition implies that the recombination is fully diffusion-controlled, which has been found to be true in various liquid hydrocarbons (Allen and Holroyd, 1974). [The inner boundary condition can be suitably modified for partially diffusion-controlled reactions, which, however, does not seem to have been done.]... 

Of the three isomeric C3H4 hydrocarbons allene (propadiene, 1), cyclopropene (2), and propyne (3), cyclopropene (2) possesses the highest heat of formation. ... 

The hydrocarbon allene, H2C=C=CH2, is obtained indirectly from petroleum and used as a precursor for several types of plastics. What is the hybridization of each C atom in allene Draw a bonding picture for allene with lines for cr bonds, and show the arrangement of the tt bonds. Be sure to represent the geometry of the molecule in three dimensions. 

Isothiocyanates (formerly known as mustard oils, 8-136) are compounds with a cumulated system of double bonds belonging to the heterocumulenes, compounds that are formally derived from the hydrocarbon allene (H2C=C=CH2). In small quantities, isothiocyanates are often accompanied by isomeric thiocyanates. Related cyanates and isocyanates do not occur in foods. 

The stability of the various cumulenic anions depends to a large extent upon the nature of the groups linked to the cumulenic system. Whereas solutions of lithiated allenic ethers and sulfides in diethyl ether or THF can be kept for a limited period at about O C, the lithiated hydrocarbons LiCH=C=CH-R are transformed into the isomeric lithium acetylides at temperatures above about -20 C, probably via HC C-C(Li )R R Lithiated 1,2,4-trienes, LiCH=C=C-C=C-, are... 

A solution of 0.20 mol of butyl lithium in about 140 ml of hexane was cooled to -6Q°C and 140 ml of dry THF were added. The mixture was cooled to about -80 C (liquid nitrogen bath) and 0.23 mol of the allenic hydrocarbon (see Chapter VI, Exp. 1, 2, 44) was added in 5 min (methylal1ene was added as a 1 1 solution in THF). The solutions were kept for 1 h at -55°C. Into another 1-1 flask (see also Fig. 1, but without a dropping funnel), cooled at -90°C by immersion in liquid nitrogen, was poured a solution of dry carbon dioxide (from a cylinder) in 130 ml of dry THF. This solution was obtained by introducing about 40 g of carbon dioxide (note 1) into the THF at -90°C. The gas inlet was removed from the second flask and the solution of the lithiated allene (still cooled below -60 C) was poured... 

Heat Capacity. The multiple property estimation methods for constant pressure ideal-gas heat capacities cover a broad range of organic compounds (188,216,217). Joback s method (188) is the easiest to use however, usage of all these methods has been recommended only over the range 280—1100 K (7). An accurate method for ideal-gas heat capacities (constant pressure), limited to hydrocarbons, has been presented (218) that involves a fit of seven variables, and includes steric, ring, branching, alkene, and even allene corrections. 

Analogy between the Delocalized Orbitals of a Hydrocarbon Skeleton (Ethylene, Ethane, Allene, Propane, etc.) and the T Delocalized Orbitals of Conjugated Chains... 

Values found for interatomic distances and bond angles in the thirteen hydrocarbons studied are given in Table XIV. The carbon-carbon singlebond distance is found to have the constant value 1.54 = = 0.02 A., being unaffected by the presence of an adjacent double bond or benzene nucleus (provided that it does not form part of a conjugated system). The carbon-carbon double-bond distance in allene and acetylene has the value 1.34 A. This is 0.04 A. less than that formerly given by the table of covalent radii, which has accordingly been revised. The effect of the revision on the bond distance-resonance curve is discussed. 

We review here results of computer simulations of monolayers, with an emphasis on those models that include significant molecular detail to the surfactant molecule. We start with a focus on hydrocarbon chains and simple head groups (typically a COOH group in either the neutral or the ionized state) and a historical focus. A less comprehensive review follows on simulations of surfactants of other types, either nonhydrocarbon chains or different head groups. More detailed descriptions of the general simulation techniques discussed here are available in a book dedicated to simulation techniques, for example, Allen and Tildesley [338] or Frenkel and Smit [339],... 

Coates JD, J Woodward, J Allen, P Philip, DR Lovley (1997) Anaerobic degradation of polycyclic aromatic hydrocarbons and alkanes in petroleum-contaminated marine harbor sediments. Appl Environ Microbiol 63 3589-3593. 

Allen CCR, DR Boyd, F Hempenstall, MJ Larkin, ND Sharma (1999) Contrasting effects of a nonionic surfactant on the biotransformation of polycyclic aromatic hydrocarbons to cw-dihydrodiols by soil hacierva.. Appl Environ Microbiol 65 1335-1339. 

The US fire code covers installation and use of gaseous oxygen-fuel gas systems for welding and cutting, for the thermodynamically unstable fuels acetylene, MAPP (methylacetylene-allene-propene-propane mixtures), and the stable hydrocarbons propane or butane. 

The double bonds of allene are said to be cumulated because one carbon (the central carbon) participates in two double bonds, i) Hydrocarbons whose molecules have cumulated double bonds are called cumulenes. 

While the variation of the mean thermalization length among different liquid hydrocarbons under high-eneigy irradiation has been well documented (see, e.g., Schmidt and Allen, 1968,1970), the question of the dependence of thermalization... 

Table 10.4 lists the values of trap density and binding energy obtained in the quasi-ballistic model for different hydrocarbon liquids by matching the calculated mobility with experimental determination at one temperature. The experimental data have been taken from Allen (1976) and Tabata et ah, (1991). In all cases, the computed activation energy slightly exceeds the experimental value, and typically for n-hexane, 0/Eac = 0.89. Some other details of calculation will be found in Mozumder (1995a). It is noteworthy that in low-mobility liquids ballistic motion predominates. Its effect on the mobility in n-hexane is 1.74 times greater than that of diffusive trap-controlled motion. As yet, there has been no calculation of the field dependence of electron mobility in the quasi-ballistic model. 

Adjacent polyenes are hydrocarbons with double bonds between each pair of atoms in the polyene system they are called cumulenes2. Two types of cumulenes exist those with an even number of adjacent double bonds and those with an odd number. The former can exhibit chirality, the latter geometric isomerism. Allenes (propadienes) are the simplest members of the even-numbered type of cumulenes. 

Acetylene is sufficiently acidic to allow application of the gas-phase proton transfer equilibrium method described in equation l7. For ethylene, the equilibrium constant was determined from the kinetics of reaction in both directions with NH2-8. Since the acidity of ammonia is known accurately, that of ethylene can be determined. This method actually gives A f/ acid at the temperature of the measurement. Use of known entropies allows the calculation of A//ac d from AG = AH — TAS. The value of A//acij found for ethylene is 409.4 0.6 kcal mol 1. But hydrocarbons in general, and ethylene in particular, are so weakly acidic that such equilibria are generally not observable. From net proton transfers that are observed it is possible sometimes to put limits on the acidity range. Thus, ethylene is not deprotonated by hydroxide ion whereas allene and propene are9 consequently, ethylene is less acidic than water and allene and propene (undoubtedly the allylic proton) are more acidic. Unfortunately, the acidity of no other alkene is known as precisely as that of ethylene. 

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