SAYTZEFF RULE PDF
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 some cases, the stereochemistry of the starting material can prevent the formation of the Zaitsev product.
Formation of the Zaitsev product requires elimination at the 2-position, but the isopropyl group — not the proton — is anti -periplanar to sayttzeff chloride leaving group; this makes elimination at the 2-position impossible.
From Wikipedia, the free encyclopedia. Markovnikov, who published in what is now known as Markovnikov’s ruleand Zaitsev held conflicting views regarding elimination reactions: The saytzefd of the base also increases the Hoffmann product at the cost of the Zaitsav product. Elimination Reaction for some alcohols and alkyl halides will result in different alkene products, and Saytzeff or Zaitsev Rule is used to determine the major product. As a result, the conformation saytzedf for the formation of the Zaitsev product is less energetically favorable than the conformation required for the formation of the Hofmann product.
Justus Liebig’s Annalen der Chemie. To make it easier to visualise, we can box up the alkene and count the number of alkyl groups attached to the alkene. Zaitsev was not the first chemist tule publish the rule that now bears his name. As a result, this particular reaction produces only the Hofmann product. Upper Saddle River, NJ: C Brown had suggested that steric factors govern such elimination reactions. Zaitsev had cited Popov’s paper in previous work and worked at the University of Kazan, and was thus probably aware of Popov’s proposed rule.
It is less substituted hence the minor product. These intramolecular interactions are relevant to the ruule of products in the Hofmann elimination reaction, which converts amines to alkenes.
Justus Liebigs Annalen der Chemie. As a result, the Hofmann Product is typically favored when using bulky bases.
Zaitsev’s rule – Wikipedia
Therefore 2 different alkene products, butene and butene can be formed. Also, alkyl groups are sterically large, and are most stable when they are far away from each other. For a step-by-step guide to predict the major product using Saytzeff Rule, check out this video lesson now!
It also favors the sayrzeff of the Hofmann product, and for the same reasons. Because the proton at this position has the correct orientation relative to the leaving group, elimination saytzecf and does occur.
In an alkane, the maximum separation is that of the tetrahedral bond angle, Retrieved from ” https: The rule makes no generalizations about the stereochemistry of the newly formed alkene, but only the regiochemistry of the elimination reaction.
Hofmann’s Rule and Zaitsev’s Rule
The increase in stability associated with additional substitutions is the result of several factors. To determine which is the major product, we have to figure out the degree of substitution for each alkene.
The quaternary ammonium group is large, and interactions with alkyl groups on the rest of the molecule are undesirable. The charged leaving groups are zaytzeff compared to neutral leaving groups.
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. Examining sagtzeff heats of hydrogenation for various alkenes reveals that stability increases with the amount of substitution.
Consequently, a terminal methyl group this has no alkyl substituent is more acidic than the internal methine proton bearing at least one alkyl substituent. Saytzeff or Zaitsev Rule states that the more substituted alkene will be the major product. The removal of the proton and the loss of the sayzeff group occur in a single, concerted step to form a new double bond.
Definition of Saytzeff Rule
Steric interactions within the substrate also prevent the formation of the Zaitsev product. While at the University of KazanRussian chemist Alexander Zaitsev studied a variety of different elimination reactions and observed a general trend in the resulting alkenes.
Perhaps one of the main reasons Zaitsev began investigating elimination reactions was to disprove his rival. For example, when menthyl chloride is treated with sodium ethoxide, the Hofmann product is formed exclusively: For butene, it has 2 alkyl groups attached to the 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.
When a small, unhindered base — such as sodium hydroxidesodium methoxideor sodium ethoxide — is used for an E2 elimination, the Zaitsev product is typically favored over the least substituted alkene, known as the Hofmann Product. In the Hofmann elimination, treatment of a quaternary ammonium iodide salt with silver oxide produces hydroxide ion, which acts as a base and eliminates the tertiary amine to give an alkene.
This page was last edited on 9 Octoberat There could be two reasons for such preferences. Hyperconjugationwhich describes the stabilizing 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 amount of energy released during a hydrogenation reaction, known as the heat of hydrogenation, is inversely related to the stability of the starting alkene: Zaitsev and Markovnikov both studied under Alexander Butlerovtaught at the University of Kazan during the same period, and were bitter rivals.
Under these conditions, the stability of the developing double bond becomes important and this leads to the thermodynamically more stable product. When 2-bromomethylbutane is treated with potassium t -butoxide instead of sodium ethoxide, the Hofmann product is favored.