Strain theory carbon atoms

Woker attempts to apply this strain theory to ring compounds, and considers that the five carbon atom ring produces less strongly odoured substances than any other and points out that, according to Baeyer s strain theory, the five carbon ring has the least internal tension. It is very doubtful if this contention is correct, since the penta-methylenes do not seem to be less strongly odoured than other polymethylene ring compounds. ... 

While correlating the stability of the ring with their size Adolf von Baeyer advanced in 1885 his famous strain theory. We know that the four valencies of a carbon atom go to the four comers... 

The strain theory agrees reasonably well with small ring compounds containing six or less carbon atoms, e.g.,... 

Extensions of the strain theory have been made, with varying success, to other hydrocarbon ring structures, saturated and unsaturated, to ring compounds in which the hydrogen atoms have been variously substituted, and to rings containing atoms other than carbon, as well as to bieyclic and polycyclic systems,... 

The 1,3-dipolar addition of azide could, in theory, give rise to a maximum of six triazoline isomers (Fig. 24), where addition across a [6,6] bond between two different types of carbon atoms in general gives rise to a pair of regio-isomers [73, 74]. Qo gains its reactivity as a result of inherent strain in the molecule. In the case of C70, having lower symmetry, the strain is not uniform over the entire molecule. Hawkin s studies on the osmylation of C70 revealed that most of the strain is localized at the poles rendering the [a-b] bond most reactive [75]. 

From the limited amount of experimental data in Table 1 each additional carbon atom increases the proton affinity by approximately 10 kcal mol Cyclopropane has a higher proton affinity than propane by ca 20 kcal mol" indicating considerable relief of strain on protonation. The calculated proton affinity of cyclopropane is at a very high level of theory and is 1.9 kcal mol lower than the experimental value, leading to the suggestion that perhaps the experimental value is slightly too high". ... 

If we assume that the Bragg model represents accurately the true shape and size of the molecule, the following conclusion, which is of importance for the theory of structure and isomerism, may be drawn Only those compounds can exist which obey the laws of space requirement outlined above, that is, which can be represented without strain by the Bragg molecular models. We arrive at the fact that two carbon atoms, united by primary valences, may not be separated by any distance greater than 1.2-1.6 A, a requirement which places definite limitations on the bridge bonds frequently formulated in organic chemistry. 

The properties of these compounds led Baeyer to consider the nature of the triple bond and the stability of rings of carbon atoms, the result being the strain theory , in which stability is related to the strain to which the valencies of carbon atoms, normally directed from the centre of the tetrahedron model towards the corners, must be subjected in the formation of closed rings. Although this theory has been to some extent modified by later work, the idea of a resistance to bending exhibited by carbon valencies has been substantiated. 

Leopold Ruzicka, a student of Hermann Staudinger, received the Nobel Prize in 1939 for disproving BaeyeFs strain theory by demonstrating that the active components of musk and civet were cyclic ketones with 16 and 17 carbon atoms in the rings. Ziegler employed the Ru hi dilution principle in the condensation of... 

A consequence of the theory of the tetrahedral carbon atom was that the bond angle at a single-bonded carbon atom should be 109 28 . In 1885 Adolf von Baeyer (1835-1917) introduced his strain theory, which stated that five- and six-membered rings were stable compared to rings of other sizes because the distortions from the tetrahedral angle were smallest in these cases. Baeyer was making the assumption that the carbon atoms in cyclic compounds were all coplanar. 

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