Functional isomerism

It is very common for a given molecular formula to be capable of representing molecules that have different functional groups. A simple example is C2H60, which may exist either as an alcohol or an 

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For optimal performance of dual function isomerization catalysts based on zeolite Y or mordenite, extensive removal of sodium is necessary. The finished catalyst must be highly crystalline, and the finely dispersed metallic hydrogenation function should be well distributed throughout the catalyst particles. The proposed mechanism explains the stabilizing influence on conversion and the suppression of cracking reactions by addition of the metallic hydrogenation function to the active acidic catalyst base. 

Table V. Development of Dual-Functional Isomerization Catalyst Systems" (27)...

Scheme XIV shows the reaction path of dual functional isomerization with its side-reactions which detract from perfect selectivity. For a given high activity of the acidic component Y, the temperature requirement for (intermediate) olefin isomerization activity drops rapidly as we go from low carbon number to high carbon number paraffins. This is pictured purely qualitatively in Fig. 14. A typical metal component such as platinum-...

This is a special type of functional isomerism. In this case, different functional groups are present, and these isomers, which are called tautomers, are often in... 

Skeletal, Positional, and Functional Isomerism in Alkenes and Alkynes... 

Functional Isomerism Section 3.4 Six functional isomers with the formula C5H10O... 

The combined liquid effluent from the fluidized-bed run was collected, and a complete analysis was made. The data are shown in Table V. The extensive isomerization taking place is of some interest all of the C6 paraffins except diisopropyl are present in the effluent, along with cyclohexane-methylcyclopentane, MCH-dimethylcyclopentane, etc. Nickel is, of course, known to have isomerizing activity, but in addition the catalyst may be functioning as a dual-function isomerization catalyst. 

Two levels of comparison are used to describe the molecular structure. The first level excludes three-dimensionality and comprises substances having the same set of atoms but differing in how they are connected in the molecule. Constitutional (structural) isomers are isomers that diDer in the sequence in which atoms are connected to one another, so they can contain different functional groups and/or bonding patterns (e.g., branching). The constitution of molecules (number, kind, and connectivity of atoms) may be represented by a two-dimensional space. There are five types of constitutional (structural) isomerism chain isomerism, positional isomerism, functional isomerism, metamerism, and tautomeiism. 

Functional isomerism, another kind of structural isomerism, occurs when substances have the same molecular... 

Zhu S-B, Lee J, Robinson G Wand Lin S H 1989 Theoretical study of memory kernel and velocity correlation function for condensed phase isomerization. I. Memory kernel J. Chem. Phys. 90 6335-9... 

Take the Final Function Value of TINKER as the steric energy for this calculation. Compare the results with each other and with a standard value from a good elementar-y organic chemistry text (e.g., Ege, 1994). Calculate for the reaction cis trans and compare it with a standard text and with Kistiakowsky s original value. Kistiakowsky s original work was carried out at 355 K, but the temperature difference between 298 K and 355 K cancels for this isomerization. 

A more quantitative approach to the influence of the thiazole ring on the reactivity of a lateral functional chain was made in a recent study by Noyce and Fike (383), already discussed in Section 10.4. The first-order rates of solvolysis for three isomeric 1-thiazolylethyl chlorides were determined in 80% ethanol. The order of relative reactivity observed. 

Write structural formulas or build molecular models and give the functional class and substitutive names of all the isomeric alcohols that have the molecular formula C4H10O... 

Historically, the isomerization catalysts have included amorphous siUca-aluminas, zeoHtes, and metal-loaded oxides. AH of the catalysts contain acidity, which isomerizes the xylenes and if strong enough can also crack the EB and xylenes to benzene and toluene. Dual functional catalysts additionally contain a metal that is capable of converting EB to xylenes. 

Dual Function Catalytic Processes. Dual-function catalytic processes use an acidic oxide support, such as alumina, loaded with a metal such as Pt to isomerize the xylenes as weH as convert EB to xylenes. These catalysts promote carbonium ion-type reactions as weH as hydrogenation—dehydrogenation. In the mechanism for the conversion of EB to xylenes shown, EB is converted to xylenes... 

Ethers, such as MTBE and methyl / fZ-amyl ether (TAME) are made by a catalytic process from methanol (qv) and the corresponding isomeric olefin. These ethers have excellent octane values and compete on an economic basis with alkylation for inclusion in gasoline. Another ether, ethyl tert-huty ether (ETBE) is made from ethanol (qv) and isobutylene (see Butylenes). The cost and economic driving forces to use ETBE vs MTBE or TAME ate a function of the raw material costs and any tax incentives that may be provided because of the ethanol that is used to produce it. 

Paraffin Isomerization. Another weU-estabhshed commercial process which employs zeoflte catalysts is the isomerization of normal paraffins into higher octane, branched isomers. The catalyst for the Hysomet process of the Shell Oil Co. is dual-functional, and consists of a highly acidic, latge-pote zeoflte loaded with a small amount of a noble-metal hydrogenation component. This catalyst possesses the same... 

Two-iing cycloaliphatic diamines such as methylenedi(cyclohexylaniine) (MDCHA), histoiically misnamed bisamino cyclohexyhnethane), oi PACM, also exhibit critically dependent fundamental physical properties as a function of configurational isomerism, the simplest and most important being melting point. 

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