Definition of Saytzeff Rule. What is the Saytzeff Rule? Dehydrohalogenation of secondary- and tertiary-alkyl halides proceeds by the preferential removal of the . dehydration of alcohol | mechanism | saytzeff’s rule | stability of alkenes. 22 Jul The Zaitsev’s Rule (or Saytzeff rule) draws our attention to the alternate possibility . On elimination of HX, the more stable olefin is obtained (Fig.
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In these situations, a less sterically hindered proton is preferentially abstracted instead.
How to predict Major Product for Elimination Reaction. As a result, the Hofmann product is formed preferentially.
While Zaitsev’s paper was well referenced throughout the 20th century, it was not until the s that textbooks began using the term “Zaitsev’s rule. So by looking at the number of alkyl groups attached to the alkene, the degree of substitution and hence major and minor products can be determined. As a result, the conformation necessary for the formation of the Zaitsev product is less energetically favorable than the conformation required for the formation of the Hofmann product.
While effective at predicting the favored product for many elimination reactions, Zaitsev’s rule is subject to many exceptions. Hyperconjugationwhich describes the saytzefg interaction between the HOMO of the alkyl group and the LUMO of the double bond, also helps explain the influence of alkyl substitutions on the stability of alkenes.
The increase in stability associated with additional substitutions saygzeff the result of several factors. It also favors the formation of the Hofmann product, and for the same reasons.
Saytzeff Rule, Zaitsev Rule: Perhaps one of the main reasons Zaitsev began investigating elimination reactions was to disprove his rival. There could be two reasons for such preferences.
As a result, this particular reaction produces only the Hofmann product.
This result is due to the stereochemistry of the starting material. In order for the Hofmann product to form, elimination must occur at the 6-position.
In the Hofmann elimination, the least substituted alkene is typically favored due to intramolecular steric interactions. Under these conditions, the stability of the developing double bond becomes important and this leads to the thermodynamically more stable product. In an alkane, the maximum separation is that of the tetrahedral bond angle, To determine which is the major product, we have to figure out the degree of substitution for each alkene.
In regards to orbital hybridizationa bond between an sp 2 carbon and an sp 3 carbon is stronger than a bond between two sp 3 -hybridized carbons.
Aleksandr Nikolaevich Popov saytzetf an sagtzeff rule similar to Zaitsev’s in and presented his findings at the University of Kazan in It is less substituted hence the minor product. Tule page was last edited on 9 Octoberat The removal of the proton and the loss of the leaving group occur in a single, concerted step to form a new double bond. As a result, the separation between alkyl groups is greatest in the most substituted alkene. In other projects Wikimedia Commons. Examining the heats of hydrogenation for various alkenes reveals that stability increases with the amount of substitution.
E2 eliminations require anti -periplanar geometry, in which the proton and leaving group lie on opposite sides of the C-C bond, but in the same plane.
The sahtzeff leaving groups are large compared to neutral leaving groups. Justus Liebig’s Annalen der Chemie. These intramolecular interactions are relevant to the distribution of products in the Hofmann elimination reaction, which converts amines to alkenes. Upper Saddle River, NJ: In E2 elimination reactions, a base abstracts a proton that is beta to a leaving group, such as a halide.