Strain in organic molecules

Keep in mind the three different types of strain in organic molecules ... 

The Hiickel molecular orbital model and its applications in organic chemistry are discussed in a three-volume series of books. Heats of hydrogenation data have been collected and discussed in a useful short review Chemical Abstracts data retrieval has been covered through to the end of 1974. Allied to this is an extensive review of the nature of strain in organic molecules. Other major reviews deal with the biosynthesis of sesquiterpenes, the use of inductive substituent constants to assess the effect of polar substituents on organic reaction rates, and non-classical ions. ... 

R. Boese, Structural Studies of Strained Molecules , in Advances in Strain in Organic Chemistry (Ed. B. Halton), Vol. 2, JAI Press, London, (1992), p. 191. 

An interesting study of the products of cubane hydrogenolysis was published by Stober, Musso and Osawa (39). In this reaction the authors found [2.2.2]bicyclooctane (83) to be the main product tetracyclo[4.2.0.0 .0 ]-octane (84) and tricyclo[4.2.0.0 ]octane (85) were identified as intermediates. The experimental findings have been rationalized by means of MM study of possible products of the reaction. It should be stressed that MM is mainly used to determine spatial structure and strain of organic molecules, and the method is seldom applied to explain the reactivity and course of reactions as has been done by the Osawa group. 

For reviews Greenberg A, Liebman JF (1978) Strained organic molecules. Academic Press, New York, p 153 (b) Rosenfeld SM, Choe KA (1983) In Keehn PM, Rosenfeld SM (eds) Cyclo-phanes. Academic Press, New York, vol 1, p 311 (c) Bickelhaupt F, de Wolf WH (1988) Reel. Trav. Chim. Pays-Bas 107 459 (d) Bickelhaupt, F (1990) Pure Appl. Chem. 62 373 (e) Bickelhaupt F, de Wolf WH (1993) In Halton B (ed) Advances in strain in organic chemistry. JAI Press, Greenwich, Connecticut, vol 3, p 185 (f) Kane VV, de Wolf WH, Bickelhaupt F, Tetrahedron (to be published)... 

Brumlik Framework Molecular Model Kit (ISBN 0-13-330076-5) Models constructed with this kit allow students to see the relationship between atoms in organic molecules, including precise interatomic distances and bond angles. The flexible bonds can form strained systems, with the amount of bend in the bonds giving a qualitative idea of the amount of strain. 

In this chapter we have learned many of the rules of bond formation and of conformation. Although there are only a few kinds of bonds in organic molecules, they can be combined in an infinite number of ways, sometimes leading to molecules whose existence defies our expectations. For example, using just C—C and C—H bonds, chemists have been able to synthesize structures such as cubane, prismane, and bicyclo[1.1. Ojbutane, materials that have incredible strain built into their structures. Strained compounds are also found in nature, with one recent discovery being pentacycloanammoxic acid, a material isolated from a particular bacterial strain. This compound is also known as a ladderane because it has a connected set of five 4-membered rings that exist in three-dimensional space like a ladder, or staircase. 

Many highly strained compounds containing small rings in fused systems have been prepared, showing that organic molecules can exhibit much more strain than... 

Most of the organic pollutants described in the present text act at relatively low concentrations because they, or their active metabolites, have high affinity for their sites of action. If there is interaction with more than a critical proportion of active sites, disturbances will be caused to cellular processes, which will eventually be manifest as overt toxic symptoms in the animal or plant. Differences between species or strains in the affinity of a toxic molecule for the site of action are a common reason for selective toxicity. 

Finally, in the sense that the imposition of conformational restrictions or specific solvent effects on an organic molecule are forms of strain, non-covalent catalysis by the cycloamyloses may provide a simple model for the investigation of strain and distortion effects in enzymatic reactions. 

Atlantic Richfield Company has reported strains of Pseudomonas sp. CB1 (ATCC 39381) [108] and Acinetobacter species CB2 [109] (ATCC 53515) to be effective for the removal of sulfur from organic molecules found in petroleum, coal, etc. In fact, the aerobic and heterotrophic soil microorganisms Pseudomonas CB1 and Acinetobacter CB2 were reported to convert thiophene sulfur into sulfate, using a bench-scale continuous bioreactor. The direct contact with Illinois 6 coal reduced the organic sulfur content in about 40% to 50%. As already mentioned, most of this work was carried out on coal. Further work was not pursued probably due to decrease in coal usage or due to the economics of the processes. 

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