Advanced Organic
Chemistry Dr. M. J.
Wieder
Consider the following ring-closure reaction:
Propose a labeling experiment to differentiate between the two mechanistic pathways shown below. Explain what results one would expect in each case.
For each of the following reactions, provide a plausible mechanism to account for the data presented:
a) The reaction below proceeds with retention of configuration.
b) Treatment of either epoxide (I) or (II) with aqueous hydroxide gives epoxide (III).
When R = alkyl group, both cyclic products are obtained
When R = phenyl, only the cyclohexanone product is obtained
Consider the decomposition-rearrangement reaction of the following azo compound:
Two mechanistic pathways have been proposed to account for the above reaction. Pathway (I) involves a concerted rearrangement, whereas Pathway (II) involves the formation of an acylium cation and phenoxide anion which then combine to give product.
When Z = H and the X-substituent is varied, rho for the reaction equals -0.47. When X = H and the Z-substituent is varied, rho for the reaction equals +0.22. Which one of the above pathways is consistent with the data? Explain.
Suggest another approach by which one could differentiate between the two pathways. Explain any results one might expect to obtain.
Show how one could demonstrate whether or not a-cyclohexylethyl chloride (shown below) undergoes solvolysis via a carbocationic intermediate:
a) by considering rate law.
b) by considering the formation of rearrangement products
(or the lack thereof).
c) by considering kinetic isotope effects
d) by taking into account optical activity considerations.
In glacial acetic acid, the tosylate ester shown below is converted to the corresponding acetate ester. A phenonium ion has been proposed as an intermediate in the reaction. Devise an experiment to support or refute the intermediacy of a phenonium ion in the acetolysis reaction.
Provide a plausible mechanism to account for the following transformation:
The Prins reaction involves the reaction of an alkene with formaldehyde in aqueous acid medium to give 1,3-diol:
Propose an experiment to differentiate between the participation of the two possible intermediates shown below:
(Hint: Pay close attention to stereochemical considerations)
Propose a mechanism to account for all of the following data:
