(a)
Interpretation:
The two carbocation intermediates that can be produced by the addition of a proton to the given allene are to be drawn.
Concept introduction:
Allenes are compounds with cumulated double bonds. Because of this, they are electron-rich and undergo electrophilic addition with Brønsted acids. In the first step, the proton adds generally to one carbon of the double bond forming a carbocation intermediate with the positive charge on the other carbon of the initial double bond.
(b)
Interpretation:
The relative stabilities of the two carbocation intermediates formed by allene are to be explained.
Concept introduction:
The stability of a carbocation depends primarily on two factors, the number of alkyl groups attached to the carbon and resonance. Resonance stabilization is generally more than the stabilization because of the inductive electron-donating nature of alkyl groups. However, resonance requires the p orbitals of adjacent carbon (or other atoms) to be parallel to the empty p orbital of the carbocation.
Want to see the full answer?
Check out a sample textbook solutionChapter 14 Solutions
Organic Chemistry: Principles and Mechanisms (Second Edition)
- (d) Consider the following catalyzed and non-catalyzed pathways of a substitution reaction of bromoethane. Draw an energy diagram for each of the following reactions (label all axes and include reactants, intermediates (if any) and products). CH3CH₂Br + HO CH³CH₂OH + B (non-catalyzed) ное CH3CH₂Br + CH3CH₂OH + 1 (catalyzed) CH3CH₂ + Brarrow_forward4) Draw the complete electron-pushing arrow mechanism for the following reductions. Explain, using resonance contributors, the regiochemistry that results in each case. ỌMe Na, MeOH ? NH3 CHO Na, MeOH ? NH3arrow_forwardThe reaction shown here is called the pinacol rearrangement. A carbocation rearrangement is believed to be involved. (a) Propose a reasonable mechanism for this reaction. (b) Suggest why the carbocation rearrangement is favorable. HO ОНarrow_forward
- (a) Draw a mechanism using the curved arrow-formalism for the O-4 methylation of thymine. Is thenucleophilic substitution in the first step an SN1 or SN2 reaction? Explain.arrow_forward(a) Give a mechanism for this reaction, showing how the two products arise as aconsequence of the resonance-stabilized intermediate.(b) The bromination of cyclohexene using NBS gives only one major product, as shown onthe previous page. Explain why there is no second product from an allylic shift.arrow_forwardaddition of hbr to a double bond with an ether (-or) substituent occurs regiospecifically to give a product in which the Br OR are bonded to the same carbon. Draw the two possible carbocation intermediates in this electrophilic addition reaction,and explain using resonance why the observed product is formed.arrow_forward
- For an SN1 reaction, which of the following is the correct order from the given statements below: (1) The nucleophile attacks both from the front and from the back of the planar carbocation. (II) The nucleophile attacks from a backside position. (II) The halide ion as the leaving group leaves initially. (IV) The halide ion as the leaving group leaves subsequently. (V) The halide ion as the leaving group leaves simultaneously as the nucleophile approaches. (VI) The product is formed. (VII) A stable carbocation is formed. (VIII) A product with inversed chirality is formed. Nu R-C-X + R-C-Nu wharrow_forward(1) Identify the nucleophile and electrophile (2) provide the mechanism using curved arrows (3) identify which elementary step is it ?arrow_forward(a) Identify the major product of the following reaction. (b) Explain why the other product is not the major product.arrow_forward
- (1) Identify the nucleophile and electrophile for each step (2) Provide the mechanism using curved arrows (3) Then identify which elementary step it isarrow_forwardProvide the complete mechanism for the reaction. Please include appropriate arrows, intermediates, and formal charges.arrow_forwardWhat is the mechanism (in detail) of the following reaction?arrow_forward
- Organic Chemistry: A Guided InquiryChemistryISBN:9780618974122Author:Andrei StraumanisPublisher:Cengage Learning