Question

The products of $HIO_4$ oxidation of the following compound is :

• A. (a)
• B. (b)
• C. (c)
• D. (d)

Answer 1

Answer: (D)

(d)

Answer 2

The starting material is a furanose derivative. Periodic acid ($HIO_4$) cleaves vicinal diols. The molecule has vicinal diols at C2-C3, C3-C4, and C4-C5.

1. Cleavage of C4-C5: The $CH_2OH$ group at C5 and the OH group at C4 are vicinal. This cleavage opens the C4-C5 bond, oxidizing C5 to formaldehyde ($HCHO$) and C4 to a carboxylic acid.

2. Cleavage of C3-C4: The OH groups at C3 and C4 are vicinal. This cleavage opens the C3-C4 bond, oxidizing C3 to an aldehyde and C4 to a carboxylic acid.

3. Cleavage of C2-C3: The OH groups at C2 and C3 are vicinal. This cleavage opens the C2-C3 bond, oxidizing C2 to a ketone and C3 to a carboxylic acid.

Considering the given options, option (d) shows a cyclic product and formic acid ($HCOOH$). The cyclic product is a 5-membered ring. If we assume the ring is formed by O-C1-C2-C3, with C1 having the $OCH_3$ group, C2 having a carbonyl group, and C3 having a carboxylic acid group, this implies:

• The C2-C3 bond was cleaved, forming a carbonyl at C2 and a carboxylic acid at C3.
• The C4-C5 bond was cleaved, forming $HCHO$ from C5.
• The C3-C4 bond was cleaved, and C4 was oxidized to a carboxylic acid. However, the product shown is $HCOOH$.

A closer look at the structure and the cleavage pattern reveals that the C2-C3 and C4-C5 bonds are cleaved.

• Cleavage of C4-C5 yields $HCHO$.
• Cleavage of C2-C3 yields a ketone at C2 and a carboxylic acid at C3.
• The remaining part, including the ring oxygen, C1, C2, and C3, forms the cyclic product.

The structure of the cyclic product in option (d) corresponds to the fragment O-C1-C2-C3 where C2 is a ketone and C3 is a carboxylic acid. The $HCOOH$ is formed from the C4 and C5 fragment. This happens if C4 is oxidized to $HCOOH$ and C5 is oxidized to $HCHO$. This is not consistent with standard vicinal diol cleavage.

Let's re-evaluate the common outcome of $HIO_4$ oxidation on sugars. It cleaves C-C bonds between carbons bearing hydroxyl groups. If the starting material is a furanose with OH at C2, C3, C4, and C5:

• Cleavage of C4-C5 gives $HCHO$ and a carboxylic acid from C4.
• Cleavage of C3-C4 gives an aldehyde from C3 and a carboxylic acid from C4.
• Cleavage of C2-C3 gives a ketone from C2 and a carboxylic acid from C3.

The product in (d) is a cyclic compound and $HCOOH$. The cyclic compound has a carbonyl at C2 and a carboxylic acid at C3. This suggests cleavage of C2-C3. The $HCOOH$ implies that C4 was oxidized to formic acid. This can happen if C4 was part of a fragment that yielded formic acid.

Given the options, the most plausible outcome is the cleavage of C2-C3 and C4-C5 bonds. Cleavage of C4-C5 results in $HCHO$. Cleavage of C2-C3 results in a ketone at C2 and a carboxylic acid at C3. The cyclic product shown in (d) is consistent with this cleavage pattern, forming a 5-membered ring. The $HCOOH$ product is unusual in this context if C4 is oxidized to a carboxylic acid. However, among the given choices, (d) is the most representative of the expected products from periodic acid cleavage of such a structure, assuming some specific oxidation pathways for the resulting fragments.