In a hypochlorite oxidation reaction, cyclohexanol plus NaOCL & aq HOAc results in cyclohexanone. The intermediate in this reaction in ROCl where R = cyclohexyl.
a.) Show how this intermediate decomposes to product in a E2-like reaction even at pH = 4-5; consider what the likely base is.
b) Hypochlorous esters of primary & secondary alcohols are hard to store, whereas t-BuOCL is commercially available. Why doesn't it undergo the reaction in part a.)?
Nevermind! Figured it out :)
Please! What is the answer? Enlighten me!
To answer these questions, we need to understand the mechanism of the hypochlorite oxidation reaction and the factors that affect the reaction. Let's break down each question:
a) The reaction proceeds via an E2-like mechanism, which means it involves a concerted elimination of a leaving group (ROCl) and a proton from the adjacent carbon. In this case, the intermediate ROCl decomposes to give cyclohexanone in the presence of a likely base with a pH of 4-5.
Here's a step-by-step explanation of how this reaction occurs:
1. At pH 4-5, the likely base is acetate ion (CH3COO-). Acetate ion is formed from acetic acid (HOAc) by accepting a proton. It acts as a base in this reaction to abstract a proton from the adjacent carbon, generating a leaving group, chloride ion (Cl-).
2. The chloride ion (Cl-) now acts as a nucleophile, attacking the carbon to which it is attached in the ROCl intermediate. This attack leads to the elimination of ROCl and the formation of a double bond. Simultaneously, the acetate ion (CH3COO-) accepts the proton from the adjacent carbon forming acetic acid (HOAc).
3. The result of this elimination is the formation of cyclohexanone as the product. The double bond is formed between the carbons that were originally attached to the R group in the ROCl intermediate.
In summary, the ROCl intermediate decomposes to cyclohexanone through an E2-like reaction involving the abstraction of a proton by acetate ion, attack of chloride ion, and subsequent elimination.
b) Hypochlorous esters of primary and secondary alcohols are difficult to store because they are highly reactive and tend to undergo unwanted side reactions. On the other hand, t-BuOCl (tert-butyl hypochlorite) is commercially available and more stable. This stability is due to the presence of a bulky tert-butyl group in t-BuOCl, which makes it less prone to undergoing the E2-like reaction described in part a).
The tert-butyl group in t-BuOCl is sterically hindered, meaning it creates a greater spatial separation between atoms, making it more difficult for the base (acetate ion) to abstract a proton and initiate the elimination process. As a result, t-BuOCl is less likely to undergo the E2-like reaction, making it more suitable for storage as a reagent.
In conclusion, the stability of t-BuOCl is attributed to the steric hindrance provided by the tert-butyl group, which prevents or slows down the E2-like reaction described in part a), while hypochlorous esters of primary and secondary alcohols are less stable and more reactive.