Problem 190 - A Complete Resource Book in Chemistry for JEE Main

Question

Match list I (organic compounds oxidized by \(\mathrm{HIO}_{4}\) ) with list II (products of HIO oxidation) and select the correct answer: List I 1\. \(\mathrm{CH}_{3} \mathrm{COCHO}\) 2\. 1,2 -cyclohexanedione 3\. \(\mathrm{PhCH}(\mathrm{OH}) \mathrm{CHO}\) 4\. \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}(\mathrm{OH}) \mathrm{COCH}_{3}\) List II (i) \(\mathrm{PhCH}=\mathrm{O}+\mathrm{HCOOH}\) (ii) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CHO}+\mathrm{HOOCCH}_{3}\) (iii) \(\mathrm{HOOC}\left(\mathrm{CH}_{2}\right)_{4} \mathrm{COOH}\) (iv) \(\mathrm{CH}_{3} \mathrm{COOH}+\mathrm{HCOOH}\) The correct matching is:

Step-by-Step Solution

Answer

1-iv, 2-iii, 3-i, 4-ii

Step 1: Understand the Process of Oxidation by 10

Oxidation by periodic acid (10) generally targets vicinal diols, cleaving the carbon-carbon bond between the hydroxyl groups and oxidizing them to carbonyl groups (aldehydes and ketones). This reaction can also affect structures such as 1,2-diols, or carbonyl compounds that can form diols by tautomerization, leading to further breakdown products.

Step 2: Analyzing Compound 1: 1310CHCHO

For compound 1, 1310CHCHO (a diketone adjacent to each other), there is no formation of a diol possible. Therefore, oxidation by 10 will directly break the diketone structure, yielding two carboxylic acids, resulting in 10310 + HCOOH (option iv).

Step 3: Analyzing Compound 2: 1,2-Cyclohexanedione

Compound 2, 1,2-cyclohexanedione, can be thought of as having the potential for diol formation. Upon oxidation by 10, it cleaves into hexanedioic acid (adipic acid), which is 100C(CH_2)_4COOH (option iii).

Step 4: Analyzing Compound 3: 10CH(OH)CHO

Compound 3, 10CH(OH)CHO, is a hydroxy aldehyde. 10 cleaves the C-C bond, leading to the formation of benzaldehyde (10CHO) and formic acid (HCOOH), corresponding to (i).

Step 5: Analyzing Compound 4: 10CHCH_2CH(OH)COCH_3

Compound 4 has a structure where the hydroxyl group is adjacent to a carbonyl group, enabling diol type cleavage. This results in further breakdown into two products: propionaldehyde (10CH_2CHO) and acetic acid (HOOCCH_3), corresponding to (ii).

Step 6: Matching Lists I and II

Now that we've identified the products for each reactant, we assign them to the options: \(1 ightarrow iv, 2 ightarrow iii, 3 ightarrow i, 4 ightarrow ii\). Therefore, the correct matches are: 1 with iv, 2 with iii, 3 with i, and 4 with ii.

Key Concepts

Periodic Acid Oxidation

Periodic acid () is a reagent known for its ability to oxidize vicinal diols, breaking down complex molecules into simpler ones. When a compound containing vicinal diols (two hydroxyl groups on adjacent carbon atoms) is treated with periodic acid, a reaction occurs where the  attacks the carbon-carbon bond between the diols. This results in the cleavage of the bond and the formation of two separate carbonyl groups.
This reaction is critical in organic chemistry, particularly when trying to simplify complex molecules for further study or synthesis.
Key features of periodic acid oxidation include:

• Specificity: It targets vicinal diols and some carbonyl compounds that can tautomerize to form diols.
• Efficiency: It efficiently cleaves carbon-carbon bonds, which simplifies structures significantly.
• Widespread Use: It has diverse applications in organic synthesis and analytical chemistry.

By cleaving C-C bonds in vicinal diols, periodic acid transformations play a vital role in structural elucidations and various synthetic routes.

Vicinal Diols

Vicinal diols are compounds containing two hydroxyl groups attached to adjacent carbon atoms (C-C-OH-OH). These structures are particularly important in the context of oxidation reactions because they are direct targets of reagents like periodic acid.
When vicinal diols encounter periodic acid, the reaction proceeds by attacking the bond connecting the two carbon atoms, leading to the formation of two carbonyl compounds (aldehydes or ketones). This characteristic makes vicinal diols an integral focus in oxidation procedures.
Characteristics of vicinal diols include:

• Reactivity: Their chemical reactivity makes them perfect substrates for selective oxidation processes.
• Structural Role: They frequently occur in sugars and other biologically significant molecules.
• Tautomerization Potential: Some carbonyl compounds can convert to vicinal diols in situ, making the overall mechanism more dynamic.

Understanding vicinal diols is crucial for predicting outcomes of oxidation reactions and designing synthetic pathways.

Carbonyl Compounds

Carbonyl compounds are characterized by the presence of a carbon-oxygen double bond (C=O), commonly found in aldehydes, ketones, carboxylic acids, and esters. These functionalities are central to a variety of chemical reactions, including oxidation processes.
In the context of periodic acid oxidation, carbonyl compounds may be further oxidized if they can form diols in a tautomeric equilibrium or undergo specific rearrangements.
Key aspects of carbonyl compounds include:

• Presence of Carbonyl Group: Central to their reactivity due to the polar nature of the C=O bond.
• Versatility in Reactions: They participate in a wide range of reactions, from nucleophilic additions to redox reactions.
• Importance in Synthesis: Carbonyl chemistry is foundational in both industrial processes and laboratory syntheses.

By understanding the behavior and reactivity of carbonyl compounds, chemists can predict and manipulate the outcomes of such oxidation reactions to achieve desired structural transformations.