Saytzeff s rule

Hofmann s Rule is valid for all intramolecular eliminations and for the Hofmann Elimination. Most bimolecular eliminations will follow Saytzeff s Rule. 

Saytzeff s rule) An elimination usually gives the most substituted alkene product. Zaitsev s mle does not always apply, but when it does, the reaction is said to give Zaitsev orientation, (p. 263)... 

Dehydration. Burgess el a .2 reported that the reagent is useful for dehydration of simple alcohols. The reaction is a stereospecific cis elimination and follows Saytzeff s rule. Crabbe and Leon3 have used this procedure with various steroidal secondary and tertiary alcohols. They conclude that the nature of the alcohol group, the configuration, and the environment are the primary factors governing the course of dehydration. The reactions are carried out at room temperature in anhydrous benzene for 2 hr. followed... 

Saytzeff s rule In elimination reactions, the major reaction product is the alkene with the more highly substituted double bond. This most-substituted alkene is also the most stable. 

Removal of hydrogen halide (HX) in the preparation of haloolefins is governed by Saytzeff s rule that the proton is removed preferentially from the carbon carrying the smallest number of hydrogen atoms.344 Removal of HX thermally or by aqueous-alcoholic alkali is important for laboratory work but particularly so on an industrial scale.10 Solid NaOH or KOH is used in the preparation of 2,3-dibromo-l-propene from 1,2,3-tribromopropane as described... 

Unsaturated compounds are obtained in good yield and often without isomerization by pyrolysis of esters of the requisite alcohol. These pyrolyses generally proceed with considerable stereoselectivity, yielding mostly the cis-olefin. A review of pyrolytic cw-eliminations has been provided by DePuy and King.23 The experimental technique is very simple the ester is heated as liquid or vapor at 300-500°. Working up of the product is also simple since neither a solvent nor another reactant is present. Pyrolysis of 1,2-dimethyl-propyl acetate at 500° gives pure 3-methyl-1-butene in 72% yield pyrolysis of 1,3-dimethylbutyl acetate also proceeds only in one direction, yielding 4-methyl-l-butene,24 and it is to be noted that in these cases olefin formation does not follow Saytzeff s rule ... 

To answer this we follow Saytzeff s rule for most products. It states that the major alkene produced is the most highly substituted one (i.e., the one with the largest number of alkyl groups bonded to the sp -hybridized carbons). In part... 

The intermediates being electron-deficient, formation of alkene 59 is always favored in accordance with Saytzeff s rule. The highest yield of 59 is obtained from the solid state photolysis of 56 a-CD owing to a relative high 59 60 ratio and the absence of inter-molecular products. 

The values in Table 7-1 confirm Zaitsev s rule (Saytzeff s rule) ... 

Both carbonyl compounds and aUcenes are well-known to be stabilized by hyperconjugative interactions with adjacent C-H bonds. In particular, the greater thermodynamic stability of more substituted alkenes, illustrated in Figure 6.27, serves as the basis of Zaitsev s rule (often re-transliterated with German spelling as Saytzeff s rule) in eliminations. The formation of more substituted alkenes is more favored because of their hyperconjugative stabilization. 

Braida, B., Prana, V., Hiberty, P. C. (2009). The Physical Origin of Saytzeff s Rule. Angewandte Chemie International Edition, 48(31), 5724-5728. 

The cationic reaction pathway also allows for predictable effects on differential substrate substitution. In the rate-limiting step, the distribution of charge (marked by ) changes from C(l), C(3) and C(5), in pentadienylic cation 18, to C(2) and C(4), in cyclopentenylic cation 19. Therefore, substituents that stabilize positive charge (electron-donating groups), accelerate the reaction in the a-position (R ), or decelerate the reaction in the p-position (R ). Classically, under rather vigorous conditions, the reactions are under thermodynamic control and result in the formation of product 20, where the double bond occupies the most substituted position (Saytzeff s Rule). 

Saytzeff s Rule. When the leaving group is neutral, elimination leads mainly to the most alkylated olefin. 

In an E l elimination of HX from RX, the first (and rate determining) step is loss of X to form an intermediate carbonium ion R". The product is formed from this by removal of a proton by base. If two or more different protons can be lost, the product will be determined by the relative rates of the corresponding proton transfer reactions. Since proton transfer reactions are of BEP type (p. 240), the most stable olefin should then be favored. Indeed E l reactions always follow Saytzeff s rule except in cases where steric hindrance favors an alternative route. 

The same six center-type process may provide an explanation for the peculiar regioselectivity of organometal-promoted eliminations. In violation of Saytzeff s rule and conformal with Hofmann s rule, 2-methoxyoctane produces with organoalkalis almost exclusively 1-octene. Only traces (4%) of cis- and trans-2-octene are detected. ... 

---