Baeyer s “ strain theory

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. ... 

It will be seen that whereas iodine leads to 1 2 tetra- and di-basie esters, methylene, ethylene, etc., iodides yield respectively 1 3, 1 4, etc., esters. The yields in these ring syntheses, as in most others, vary in agreement with Baeyer s Strain Theory. ... 

Mohr, E. Die Baeyersche Spannungstheorie und die Struktur des Diamanten. [Baeyer s strain theory and the structure of diamond.] Chemisches Zentralblatt 2, 1065 (1915). 

Structure A typical alicyclic hydrocarbon. It exists in two modifications called the boat and the chair, as shown. This is due to slight distortion of the bond angles in accordance with the modified version of Baeyer s strain theory. Cyclohexane has been studied extensively on a theoretical basis in a branch of advanced chemistry called conformational analysis. See conformation. 

Structure X in Figure 300 shows interpenetrating tetrahedra with carbon centers and a single bond between these carbons. Van t Hoff correctly postulated that there is free rotation about such single bonds. Structures XIa, Xlb, XII, and XIII rationalize cis and Irons isomerism (e.g., the difference between maleic acid and fumaric acid). Structure XIV explains the widespread occurrence of six-membered rings in chemistry and aspects of Baeyer s strain theory. ... 

Baeyer s strain theory applies to rings with atoms in a single plane. It is not necessary for the atoms to be in a single plane, and all sorts of odd rings can be (and are) formed in which this restriction does not hold. 

Natural dyes were duphcated in the laboratory. In 1867, Baeyer (of the strain theory ) began a program of research that eventually led to the synthesis of indigo. This achievement was, in the long run, to put the large indigo plantations in the Far East out of business. In 1868, a student of Baeyer s, Karl Graebe (1841-1927) synthesized alizarin, another important natural dye. 

The data in Figure 4.3 show that Baeyer s theory is only partially correct. Cyclopropane and cyclobutane are indeed strained, just as predicted, but cyclopentane is more strained than predicted, and cyclohexane is strain-free. Cycloalkanes of intermediate size have only modest strain, and rings of 14 carbons or more are strain-free. Why is Baeyer s theory wrong ... 

Figure 3, together with Statement 6, clarifies some surprising results from different studies on strained ring compounds and culminates in the conclusion that Baeyer s theory is valid only for silicon rings [2],... 

Finally Baeyer s theory is based on a mechanical concept of valency and served its purpose in stimulating research in the field of cyclic compounds. Now we have the electronic theory and the reactivity of olefines has been attributed to the n electrons and not on the basis of strains. 

Baeyer strain theory org chem The theory that the relative stability of penta- and hexamethylene ring compounds is caused by a propitious bond angle between carbons and a lack of bond strain. ba-or stran, the-3-re baking soda See sodium bicarbonate. bak-ir, sod-s ... 

Baeyer s theory was wrong for a very simple reason He assumed that rings are flat. In fact, though, most cycloalkanes are not flat they adopt puckered three-dimensional conformations that allow bond angles to be nearly tetrahedral. Only for three- and four-membered rings is his concept of angle strain important. 

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