Question

In: Chemistry

1. Mechanistically, what is the major difference between an E1 and E2 elimination process? 2. Why...

1. Mechanistically, what is the major difference between an E1 and E2 elimination process?

2. Why is phosphoric acid or sulfuric acid used in the E1 elimination reactin rather than HCl or HBr?

3. If the elimination reaction can result in the formation of to different alkenes which one with predominate in the product?

Solutions

Expert Solution

  1. What is the major difference between an E1 and E2 elimination process?

For E1 elimination reaction

  • unimolecular reaction, rate of reaction depends on the concentration of substrate or alkyl halide.
  • Carbocation intermediate formed.
  • it does not require strong base, attacking group.
  • tertiary alkyl halide favors E1 mostly.
  • Reactivity order of RX is 3°>2°>1°
  • Rearrangement may take place.
  • No stereospecific.
  • Follow ziatsev rule.
  • polar protic solvent good because stabilised ionic intermediate
  • Rate of reaction increases when concentration of substrate increases.

For E2 elimination reaction:

  • bimolecular reaction, rate of reaction depends on the concentration of substrate or alkyl halid as well as base or attacking nucleophile.
  • it requires strong base, nucleophile.
  • Primary alkyl halide favors E2 mostly.
  • Single step reaction.
  • Hydrogen remove from beta carbon.
  • Trans elimination because low energy consumption.
  • Anti periplanar attack.
  • Polar aprotic solvent best.
  • Phenyl group influence elimination because product alkene further stabilised by resonance.
  • Reactivity order 3°>2°>1°. No steric effect.
  • Strong nucleophile influence elimination.
  • No intermediate formed.

2. Why is phosphoric acid or sulfuric acid used in the E1 elimination reaction rather than HCl or HBr?

If H2SO4 or H3PO4, were used as acid in the reaction with alcohol then elimination reaction proceeds where as the use of HCl or HBr results in substitution reaction. This is because the HSO4– anion is a very poor nucleophile , being quite stabilized by resonance. The negative charge is delocalized over three different oxygens.

The similar is the case with phosphoric acid too

The treating of an alcohol with a strong hydrohalic acid – think HCl, HBr, or HI – resulted in the formation of alkyl halides. With a tertiary alcohol this proceeds through an SN1 mechanism. [Protonation of alcohol, then loss of H2O to form a carbocation, then attack of nucleophile on carbocation].

3. If the elimination reaction can result in the formation of two different alkenes which one with predominate in the product?

If an alcohol is treated with a strong acid (like sulfuric acid, H2SO4) and heat, you obtain one major product (an alkene) and a minor product (also an alkene).

  

The major product of an elimination reaction is the more substituted alkene. This is because the transition state leading to the more substituted alkene is lower in energy and therefore will proceed at a higher rate.

This is based on the zaitsev’s rule. It states that in a regioselective E1 or E2 reaction the major product is the more stable alkene, (i.e., the alkene with the more highly substituted double bond). For example: E1 reaction always follow Zaitsev's rule; with E2 reactions, there are exceptions


Related Solutions

-Discuss elimination reactions (E1 and E2). -Discuss Zaitseff and Hoffman orientations (or eliminations). -Define dehydration
-Discuss elimination reactions (E1 and E2). -Discuss Zaitseff and Hoffman orientations (or eliminations). -Define dehydration
Why is this not E1? Also how can I know the difference between e1 and sn1
Why is this not E1? Also how can I know the difference between e1 and sn1
What is the difference between Eo and E1/2? What is the role of salt bridge in...
What is the difference between Eo and E1/2? What is the role of salt bridge in galvanic cells? . What are the three electrodes employed in voltammetry? And what is their functions?
For each reaction below, determine whether the major reaction is SN1, SN2, E1, or E2, and...
For each reaction below, determine whether the major reaction is SN1, SN2, E1, or E2, and then draw the product.
1. how does age affect elimination problems 2. What is the difference between an indwelling catheter...
1. how does age affect elimination problems 2. What is the difference between an indwelling catheter and a straight catheter?What are some reasons why a patient would need an indwelling catheter inserted?What are some reasons why a patient would need a straight catheter?What education should be given to the patient before, during, and after the procedure?How did you do while practicing? Did you forget anything? Did you stay sterile?
1. Explain the process of creating a significance test. 2. What is the difference between a...
1. Explain the process of creating a significance test. 2. What is the difference between a z-distribution and a t-distribution? When would you use each of them. 3. How do confidence intervals and significance tests relate? 4. What does having the value of zero contained in a confidence interval for a difference tell you? 5. When do you use a matched-pairs t-test?
Question #1 a) What is the major difference between a 4:1 MUX (multiplexer) and a 2:4...
Question #1 a) What is the major difference between a 4:1 MUX (multiplexer) and a 2:4 decoder? b) How many binary inputs would be needed for a decoder with 32 mutually-exclusive outputs? Please explain why. c) A data acquisition system has only one analog-to-digital (A/D) converter. You have 12 different analog inputs to select. Which of the following would you choose? 1) 8:1 MUX 2) 4:16 decoder 3) 16:1 MUX 4) 3:8 decoder Please explain why.
1) Create a chart comparing E1, E2, SN1 and SN2 reactions. Be detailed and cover: structure...
1) Create a chart comparing E1, E2, SN1 and SN2 reactions. Be detailed and cover: structure of RX, reactivity of nucleophile, concentration of nucleophile, solvent and stereochemistry.
1. What is the difference between arguments, opinions and descriptions? 2. What is the difference between...
1. What is the difference between arguments, opinions and descriptions? 2. What is the difference between arguments and explanations, and what is the primary purpose of each?
1.What layer of the uterus is shed during menstruation and why? 2.What is the difference between...
1.What layer of the uterus is shed during menstruation and why? 2.What is the difference between sensible and insensible water loss? 3.Where is the thirst center in the brain and how does it work to make you thirsty or not?
ADVERTISEMENT
ADVERTISEMENT
ADVERTISEMENT