Zaitsev rule


REGIOSELECTIVITY IN ALCOHOL DEHYDRATION THE ZAITSEV RULE  [c.204]

The regioselectivity of dehydrohalogenation of alkyl halides follows the Zaitsev rule p elimination predominates m the direction that leads to the more highly substi tuted alkene  [c.212]

Dehydrohalogenation of alkyl halides (Sections 5 14-5 16) Strong bases cause a proton and a halide to be lost from adjacent carbons of an alkyl halide to yield an alkene Regioselectivity is in accord with the Zaitsev rule The order of halide reactivity is I > Br > Cl > F A concerted E2 reaction pathway is followed carbocations are not involved and rearrangements do not occur An anti coplanar arrangement of the proton being removed and the halide being lost characterizes the transition state  [c.222]

The regioselectivity of dehydrohalogenation of alkyl halides follows the Zaitsev rule p elimination predominates in the direction that leads to the more highly substituted alkene.  [c.212]

Dehydrohalogenation of alkyl halides (Sections 5.14-5.16) Strong bases cause a proton and a halide to be lost from adjacent carbons of an alkyl halide to yield an alkene. Regioselectivity is in accord with the Zaitsev rule. The order of halide reactivity is I > Br > Cl > F. A concerted E2 reaction pathway is followed, carbocations are not involved, and rearrangements do not occur. An anti coplanar arrangement of the proton being removed and the halide being lost characterizes the transition state.  [c.222]

Quaternary ammonium hydroxides undergo elimination on being heated. It is an anti elimination of the E2 type. The regioselectivity of the Hofmann elimination is opposite to that of the Zaitsev rule and leads to the less highly substituted alkene.  [c.958]

Zaitsev s rule as applied to the acid catalyzed dehydration of alcohols is now more often expressed in a different way elimination reactions of alcohols yield the most highly substituted alkene as the major product Because as was discussed in Section 5 6 the most highly substituted alkene is also normally the most stable one Zaitsev s rule is sometimes expressed as a preference for predominant formation of the most stable alkene that could arise by elimination  [c.205]

Alkenes are prepared by P elimination of alcohols and alkyl halides These reactions are summarized with examples m Table 5 2 In both cases p elimination proceeds m the direction that yields the more highly substituted double bond (Zaitsev s rule)  [c.221]

In 1870 Vladimir Markovnikov a colleague of Alexander Zaitsev at the Univer sity of Kazan noticed a pattern in the hydrogen halide addition to alkenes and organ ized his observations into a simple statement Markovnikov s rule states that when an unsymmetrically substituted alkene reacts with a hydrogen halide the hydrogen adds to the carbon that has the greater number of hydrogens and the halogen adds to the car bon having fewer hydrogens The preceding general equations illustrate regioselective addition according to Markovnikov s rule and the equations that follow provide some examples  [c.237]

Markovnikov s rule like Zaitsev s organizes experimental observations in a form suitable for predicting the major product of a reaction The reasons why it works will appear when we examine the mechanism of electrophilic addition m more detail  [c.238]

In 1875, Alexander M. Zaitsev of the University of Kazan (Russia) set forth a generalization describing the regioselectivity of p eliminations. Zaitsev s rule summarizes the results of numerous experiments in which alkene mixtures were produced by p elimination. In its original form, Zaitsev s rule stated that the alkene formed in greatest amount is the one that corresponds to removal of the hydrogen from the /3 carbon having the fewest hydrogens.  [c.204]

Zaitsev s rule as applied to the acid-catalyzed dehydration of alcohols is now more often expressed in a different way /3 elimination reactions of alcohols yield the most highly substituted alkene as the major product. Because, as was discussed in Section 5.6, the most highly substituted alkene is also nonnally the most stable one, Zaitsev s rule is sometimes expressed as a preference for predominant formation of the most stable alkene that could arise by /3 elimination.  [c.205]

Alkenes are prepared by P elimination of alcohols and alkyl halides. These reactions are summarized with examples in Table 5.2. In both cases, p elimination proceeds in the direction that yields the more highly substituted double bond (Zaitsev s rule).  [c.221]

Zaitsev s rule (Section 5.10) When two or more alkenes are capable of being formed by an elimination reaction, the one with the more highly substituted double bond (the more stable alkene) is the major product.  [c.1297]

With a regioselectivity opposite to that of the Zaitsev rule the Hofmann ehmma tion IS sometimes used in synthesis to prepare alkenes not accessible by dehydrohalo genation of alkyl halides This application decreased in importance once the Wittig reac tion (Section 17 12) became established as a synthetic method Similarly most of the analytical applications of Hofmann elimination have been replaced by spectroscopic methods  [c.939]

Quaternary ammonium hydroxides un dergo elimination on being heated It is an anti elimination of the E2 type The regioselectivity of the Hofmann elimina tion IS opposite to that of the Zaitsev rule and leads to the less highly substi tuted alkene  [c.958]

The least sterically hindered p hydrogen is removed by the base in Hofmann elimination reactions. Methyl groups are deprotonated in preference to methylene groups, and methylene groups are deprotonated in preference to methines. The regioselectivity of Hofmann elimination is opposite to that predicted by the Zaitsev rule (Section 5.10). Elimination reactions of alkyltrimethylammonium hydroxides are said to obey the Hofmann rule they yield the less substituted alkene.  [c.938]

With a regioselectivity opposite to that of the Zaitsev rule, the Hofmann elimination is sometimes used in synthesis to prepare alkenes not accessible by dehydrohalo-genation of alkyl halides. This application decreased in importance once the Wittig reaction (Section 17.12) becfflrre established as a synthetic method. Similarly, most of the analytical applications of Hofmann elimination have been replaced by spectroscopic methods.  [c.939]

In 1875 Alexander M Zaitsev of the University of Kazan (Russia) set forth a gen erahzation describing the regioselectivity of p eliminations Zaitsev s rule summarizes the results of numerous experiments m which alkene mixtures were produced by p elim matron In its original form Zaitsev s rule stated that the alkene formed in greatest amount is the one that corresponds to removal of the hydrogen from the f3 carbon hav mg the fewest hydrogens  [c.204]

The major product, predicted on the basis of Zaitsev s rule, is 2,3-dimethyl-2-butene. It has a tetrasubstituted double bond. The minor alkene has a disubsti- tuted double bond.  [c.213]

In 1870, Vladimir Mai kovnikov, a colleague of Alexander Zaitsev at the University of Kazan, noticed a pattern in the hydrogen halide addition to alkenes and organized his observations into a simple statement. Markovnikov s rule states that when an tinsymmetrically substituted alkene reacts with a hydrogen halide, the hydrogen adds to the carbon that has the greater number of hydrogens, and the halogen adds to the carbon having fewer hydrogens. The preceding general equations illustrate regioselective addition according to Markovnikov s rule, and the equations that follow provide some examples.  [c.237]

Maikovnikov s rule, like Zaitsev s, organizes experimental observations in a fonn suitable for predicting the major product of a reaction. The reasons why it works will appeal when we exanine the mechanism of electrophilic addition in more detail.  [c.238]


See pages that mention the term Zaitsev rule : [c.205]    [c.212]    [c.938]    [c.204]    [c.205]    [c.212]   
Carey organic chemistry (0) -- [ c.204 , c.212 , c.221 ]

Organic chemistry (0) -- [ c.204 , c.212 , c.221 ]