Isomerization, isomers

Fig. 10. Selectivities in hexane conversions versus temperature for benzene formation (Be), hydrogenolysis (Hy), methylcyclopentane formation (MCP), isomerization (ISOM), and dehydrocyclization (Dehy) (9 wt. % Pt on inert Si02).

Toluene hydrogenation (HYD), cyclohexane isomerization (ISOM) and thiophene hydrodesulfurization (HDS) tests have been performed in a high pressure fixed bed continuous flow "Catalest" unit. 

The importance of drawing chemical structures can be further illustrated by considering isomerism. Isomers are substances that have the same molecular formula but different structural formulae. Different types of isomerism are found in chemistry, e.g. geometric, optical, etc. Fig. 42.6 shows the geometric isomers of dichlorocyclopropane, i.e. cA-dichlorocyclopropane and trans-dichlorocyclopropane. 

As a preparative route mercuration of arenes suffers from a lack of selectivity often all possible ring substitution products are formed. The directing influences of substituents operate, but selectivity is poor. The initial products can isomerize. Isomer distributions in mercuration of toluene under different conditions are given in Table 3. These effects coupled with the ease of polymercuration can be disadvantagous. Mild conditions must be used to limit the extent of mercuration of five-membered heterocyclic aromatics such as pyrrole, thiophene, selenophen and furan. These are among the most reactive aromatics toward Hg salts use of HgCl2 in the presence of Na02CCH3 at RT is... 

Structural isomerism Isomers that are distinguished by having a different arrangement of bonds in the molecule. 

Berry pseudorotation. The stability of the abovementioned intermediates is additionally limited by steric factors and intramolecular overcrowding in trigonal bypiramidal structures. The more favorable isomers are A and A° due to the equatorial position of the methyl substituent of the phospholane ring. The presence of pentacoordinated intermediates was confirmed by P NMR. Nevertheless, the relative stability of isomeric isomers A -A"" is not a factor determining the stereochemical outcome of this reactions, since the substituent derived from mono-Grignard reagent is not yet present in these structures. 

Large numbers of organic compounds are possible because carbon atoms link to form chains and networks. An additional reason for the existence of so many organic compounds is the phenomenon of isomerism. Isomers are compounds that have the same molecular formula but different arrangements of atoms. 

Fatty acids containing conjugated double bonds may be present as an ester, amide or ether see suitability of respective lipid type above. The conjugated double bond system in the alkyl chain of CLA may be isomerized (Isom) or is stable (Stable) using the methylation conditions. 

Cis-trans isomerism Isomers that have the same order of attachment of their atoms, but a different arrangement of their atoms in space due to the presence of either a ring (Chapter 3) or a carbon—carbon double bond (Chapter 4). 

Isomerism Isomers are compounds with the same molecular formula (or the same simplest formula, in the case of ionic compounds) but with different arrangements of atoms. Because their atoms are differently arranged, isomers have different properties. There are many possibiUties for isomerism in coordination compounds. The smdy of isomerism can lead to information about atomic arrangement in coordination compounds. Wauer s research on the isomerism of coordination compounds finally convinced others that his views woe essentially correct. 

Another phenomenon contributing to the great variability of organic compounds is isomerism. Isomers are compounds that have exactly the same molecular formula but differ in at least one of their chemical or physical properties. 

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