File name: E1 And E2 Reactions Pdf
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In this section, we will discuss some important elimination mechanisms like E2, E1, and E1CB-type. An E2 elimination reaction is a type of organic reaction in which two substituents are . According to Zaitsev's Rule, the most stable alkene is the most substituted one. In the reaction shown below, Zaitsev's rule would suggest that product number I should form. However only . • There are 2 kinds of elimination reactions, E1 and E2. • E2 = Elimination, Bimolecular (2nd order). Rate = k [RX] [Nu: ] E2 reactions occur when a 2°or 3°alkyl halide is treated with a . Reaction Is Nuc/Base bulky? E2 yes no What kind of substrate? methyl or 1° S N2 3° yes mostly E1* 2° no mostly S N1* What kind of substrate? 2°, 3°, or stabilized 1° 1° S N2 + E2 Is Nuc/Base bulky? Unfavorable Reaction Start * Under conditions that favor a unimolecular reaction (weak nuc/base and polar protic solvent), mixtures of S N1. In this section, we will discuss some important elimination mechanisms like E2, E1, and E1CB-type. An E2 elimination reaction is a type of organic reaction in which two substituents are removed from a molecule in a one-step concerted mechanism. E2 mechanism — bimolecular elimination E1 mechanism — unimolecular elimination The E2 and E1 mechanisms differ in the timing of bond cleavage and bond formation, analogous to the SN2 and SN1 mechanisms. E2 and SN2 reactions have some features in common, as do E1 and SN1 reactions. Elimination Reactions - E2 Reaction: • Reaction is: o Stereospecific (Anti-periplanar geometry preferred, Syn-periplanar geometry possible) o Concerted - all bonds form and break at same time o Bimolecular - rate depends on concentration of both base and substrate o Favoured by strong bases Elimination Reactions – E1 Reaction: • Reaction is. The rate of an E1 reaction increases as the number of R groups on the carbon with the leaving group increases. Increasing rate of E1 reaction RCH 2 XR 2CH XR 3C X 1° 2° 3° + + + I i bili f b i RCH 2 R 2CH R 3C 1° 2° 3° ncreas ng sta ty o car ocat ons The strength of the base usually determines whether a reaction follows the E1 or E2. ModuleElimination Reactions: E1 and E2 mechanisms-Part-I 4. Comparison Between the E1 and E2 Elimination Mechanisms An elimination reaction may follow E1 or E2 mechanism depending upon several factors. Often, a reaction may proceed in either of the two pathways subject to the reaction conditions employed. These factors are listed as follows: 1.