Structural Constitutional Isomers

Give the relationships between the following pairs of stmctures. The possible relationships are same compound, cis-trans isomers, constitutional (structural) isomers, not isomers (different molecular formula). 

Photochemical chlorination of pentane gave a mixture of three isomenc monochlorides The pnncipal monochlonde constituted 46% of the total and the remaining 54% was approximately a 1 1 mixture of the other two isomers Write structural formulas for the three monochlonde iso mers and specify which one was formed in greatest amount (Recall that a secondary hydrogen is abstracted three times faster by a chlonne atom than a pnmary hydrogen)... 

Isomers are substances that have the same number and kinds of atoms, but arranged differently. Constitutional (structural) isomers, as applied to coordination compounds, are isomers whose differences involve having more than a single coordination sphere or different donor atoms on the same ligand. 

Compounds with the same molecular formula but different structures are called isomers. For example, 1-butene and 2-butene have the same molecular formula, C4H8, but structurally they are different because of the different positions of the double bond. There are two types of isomer constitutional isomers and stereoisomers. 

Toluene mononitrated 1863 Crude TNT first prepd by Wilbrand, but constitution not determined 1870 First detailed study of the prepn of 2,4,6-TNT by Beilstein and Kuhlberg 2,4,5-isomer discovered structures not established... 

Classify a pair of isomers as structural (constitutional) isomers or stereoisomers, and if the latter, as conformational or configurational (see Figure 2.8). 

As an example, consider the molecule formed from one atom each of carbon, hydrogen, and nitrogen. We can assemble these atoms in two different ways and still satisfy the octet rule. (This is another example of compounds that have the same molecular formula but a different arrangement of bonded atoms. Such compounds are called constitutional isomers or structural isomers and are very common in organic chemistry.) The structure on the left was the one used in Figure 1.6. The structure on the right is obtained if the hydrogen is bonded to the N rather than the C. 

Which of these two structures is correct Both of them satisfy the octet rule and neither has formal charges, so both are predicted to be of comparable stability. On the basis of what we have discussed so far, we cannot predict which is more stable. In fact, both of these compounds are quite stable and can be put in a bottle. But they are different compounds. Ethyl alcohol is the alcohol found in beverages. It is a liquid at room temperature. In contrast, dimethyl ether is a gas at room temperature and is quite poisonous. As was mentioned in Section 1.7, compounds such as these, with the same molecular formula but different arrangements of bonded atoms (different structures or different connectivities), are called constitutional isomers (or structural isomers). Constitutional isomerism is very common in organic compounds. This is another reason why it is necessary to show the structure of the compound under discussion rather than just the molecular formula. 

Constitutional isomers (or structural isomers) are isomers that differ in their bonding sequence that is, their atoms are connected differently. Let s use butane as an example. If you were asked to draw a structural formula for C4Hi0, either of the following structures would be correct ... 

Compounds having the same numbers and types of atoms but different structures are called isomers. Coordination compounds exhibit several of types of isomerism, and the study of these various types of isomers constitutes one of the interesting and active areas of research in coordination chemistry. Because so much of coordination chemistry is concerned with isomeric compounds, it is essential that a clear understanding of the various types of isomerism be achieved before a detailed study of structure and bonding in complexes is undertaken. Although the possibility of a substantial number of types of isomerism exists, only the more important types will be discussed here. 

The photoelectron spectra of the isomers 45 are nearly identical. The same must hold true for the isomers 112 indeed, even though compound 112 has been obtained as an inseparable mixture of anti- and ty -isomers, the sharpness of its PES demonstrates that the cation spectra of the isomers 112 are equivalent. This conclusion is further supported by the electronic-structure calculation the DET results indicate that the energy spectrum becomes less dependent on isomer constitution as the size of the system increases. In contrast to the acenedithiophenes, the difference between the PESs of the isomers 47 is substantial (Figure 23). 

There are two major classes of isomers constitutional isomers and stereoisomers. Constitutional (or structural) isomers differ in the way the atoms are connected to each other. Constitutional isomers have ... 

Chemical compounds that have the same molecular formula but different structural formulas are said to be isomers of each other. These constitutional isomers (or structural isomers) differ in their bonding sequence, i.e. their atoms are connected to each other in different ways. Stereoisomers have the same bonding sequence, but they differ in the orientation of their atoms in space. Stereoisomerism can be further divided into optical isomerism (enantiomerism) and geometrical isomerism (cis—trans isomerism). The relationships between the different types of isomerism are shown in Figure 4.1. 

Bohanec, S. and Zupon, J., Structure generation of constitutional isomers from structural fragments, J. Chem. Inf. Comput. Sci., 31, 531, 1991. 

Two kinds of isomers are important in organic chemistry. Constitutional (structural) isomers have different arrangements of atoms. Stereoisomers have the same atom arrangement but different spatial orientations. There are two types optical isomers are mirror images that cannot be superimposed, and geometric (cis-trans) isomers have different orientations of groups around a C=C bond. 

Constitutional Isomers Same Atoms Connected Differently Two compounds with the same formula, but with the atoms connected differently, are called constitutional (structural) isomers. Coordination compounds exhibit two types of constitutional isomers one involves a difference in the composition of the complex ion, the other in the donor atom of the ligand. 

MBOCA is a man-made chemical and has not been found in nature (lARC 1974). It is produced commercially by reacting formaldehyde with 0-chloraniline (HSDB 1991 lARC 1974). Pure MBOCA is a colorless crystalline solid (Smith and Woodward 1983). The technical grade of MBOCA that is available in the United States comes mainly from Japan in the form of tan/yellow fused prills or pastilles. The diamine purity is 99.8%, typically with 0.2% free o-chloroaniline (monomer). Isomers are produced as side reactions such as trimers and tetrameres-diamines with three-and four-ring structures joined by methylene groups. Isomers constitute up to 8-10% of MBOCA. The dimer makes up to 90-92% of the MBOCA produced today for coatings and cast polyurethanes. There is no commercial use for pure dimer MBOCA other than for laboratory work. 

Two compounds can have different structures because of a differing arrangement of the some groups in the positional isomerism (e.g. midine vs. pseudouridine). Compounds with the same molecular formula but with different functional groups are structural isomers (e.g. D-glucose vs. D-fructose) in structural isomerism. Positional isomers and structural isomers have different chemical and physical properties because of the different arrangement of the atoms. These two types of isomers (i.e. positional isomers and structural isomers), which differ in the manner in which atoms are connected or bonded together, are also called constitutional isomers. 

Constitutional (structural) isomers are isomers with the same molecular formula, but are different in terms of the order in which the atoms are connected... 

Coordination compounds often form isomers. Isomers are compounds with the same formula (or components) but different physical structures. There are two broad classes of isomers — constitutional, or structural isomers, and stereoisomers. Within these two categories, there are specific types of isomers, with different degrees of complexity. Figure 9-2 illustrates with a flowchart how the different types of isomers are related to one another. 

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