Question

Reaction of the glycol with periodic acid gives a fivemembered cyclic periodate. A cyclic perriodate

Short answer

Question: Describe the reaction mechanism of glycol (ethylene glycol) with periodic acid to form a five-membered cyclic periodate. Answer: The reaction of glycol with periodic acid involves the following steps: 1. Each hydroxyl group from ethylene glycol attacks the iodine atom in periodic acid, forming bonds between the oxygen and iodine atoms. 2. The L➤H-O-IO3 bond breaks, generating a positively charged iodine and a water molecule as a leaving group. 3. The oxygen connected to the iodine forms a bond with the positively charged iodine atom, creating a five-membered ring with a periodate structure. 4. Rearrangement of the periodate in the ring occurs through the migration of a double bond, producing the final five-membered cyclic periodate.

Step-by-step solution

Identify the molecules involved in the reaction

The first step is to recognize the molecules involved in the reaction. Glycol refers to ethylene glycol, which has the chemical formula HO-CH2-CH2-OH. Periodic acid is HIO4, a strong oxidizing agent that can cleave carbon-carbon bonds in certain molecules.

Understand the general mechanism of the reaction

In this reaction, a molecule of ethylene glycol will react with a molecule of periodic acid. The two hydroxyl groups (-OH) on the ethylene glycol are susceptible to the oxidizing action of the periodic acid, leading to the cleavage of the carbon-carbon bond and the formation of a five-membered cyclic periodate.

Draw the structures of the molecules involved

Before illustrating the reaction mechanism, it's essential to draw the structures of the molecules involved. Ethylene glycol (glycol): HO-CH2-CH2-OH Periodic acid (HIO4): ``` O || I-O-H || O ```

Illustrate the reaction mechanism

Here we'll show the step-by-step reaction mechanism between ethylene glycol and periodic acid. 1. Two lone pairs of oxygen from each hydroxyl group of ethylene glycol attack the central iodine atom of periodic acid, forming a bond between both oxygen and iodine atoms. ``` O || H-O-CH2-CH2-O-H + H-I-O-H ---> H-O-CH2-CH2-O-H | | || I O I-O-H || O ``` 2. The L➤H-O-IO3 bond breaks, leaving the iodine with a positive charge and creating a water molecule as a leaving group. ``` O || H-O-CH2-CH2-O-H || | || H-IO3 O-I (+) ``` 3. The oxygen that is still connected to the iodine forms a bond with the positively charged iodine atom, creating a five-membered ring with a periodate structure. ``` O || H-O-CH2-CH2-O-H \ \ I====O || O ``` 4. Rearrangement of the periodate in the ring through the migration of a double bond, resulting in the final five-membered cyclic periodate. ``` O || O-I-CH2-CH2-O-H \\ | || --O--- ``` This is a detailed explanation of how the reaction of glycol (ethylene glycol) with periodic acid leads to the formation of a five-membered cyclic periodate.

Key concepts

Ethylene Glycol

Ethylene glycol is a simple diol with the chemical formula \( HO{-}CH_2{-}CH_2{-}OH \), consisting of two hydroxyl groups attached to a two-carbon chain. It is a colorless, sweet-tasting liquid that is completely miscible with water. This compound is commonly used as antifreeze in cooling and heating systems. Another significant application is in the production of polyesters, where it acts as a precursor. Ethylene glycol's structure allows it to readily engage in chemical reactions, especially those involving oxidation due to the presence of both of its hydroxyl groups, making it a versatile compound in organic synthesis.
Its reactivity is largely due to its structure. The hydroxyl groups make it a target for reactions that involve bond formation or cleavage, especially when reacting with strong oxidizing agents such as periodic acid. These reactions often result in cleavage of the carbon-carbon bond, which can lead to smaller, more useful compounds.

Periodic Acid

Periodic acid, with the chemical formula \( HIO_4 \), is a powerful oxidizing agent. It is part of the family of oxo-acids of iodine. Its principal function in organic reactions is its ability to cleave carbon-carbon bonds adjacent to hydroxyl groups, which is crucial in glycol oxidation reactions.
In the reaction with ethylene glycol, periodic acid specifically targets the carbon atoms bonded to the hydroxyl groups. It acts by facilitating the removal of hydrogen atoms from these hydroxyl groups and the subsequent formation of a bond with iodine. This process is part of what forms the cyclic periodate structure, highlighting the usefulness of periodic acid in oxidative cleavage processes.

• Periodic acid's oxidative nature makes it particularly effective for reactions requiring precise bond cleavage, an essential skill in both laboratory and industrial chemical processes.

Oxidation Reaction

Oxidation reactions involve the loss of electrons or increase in oxidation state by a molecule, atom, or ion. In the context of ethylene glycol and periodic acid, it refers to the breaking of bonds and the formation of new ones through the process of electron transfer and transformation. This particular reaction demonstrates how ethylene glycol undergoes oxidative cleavage when exposed to periodic acid.
This reaction proceeds through a mechanism where periodic acid acts by accepting electrons from ethylene glycol. As a result, the carbon-carbon bond is cleaved, with the hydroxyl groups of ethylene glycol transforming onto oxygen-iodine bonds. This oxidative process not only changes the structure but also facilitates the formation of a new, cyclic structure. Understanding such reactions is crucial for the synthesis and development of new chemical compounds.

Carbon-Carbon Bond Cleavage

Carbon-carbon bond cleavage refers to the process whereby the bond between two carbon atoms is broken, resulting in the separation of the linked carbon atoms. This is a pivotal concept in organic chemistry because it allows transformation of organic molecules into smaller fragments or entirely different products.
In the reaction between ethylene glycol and periodic acid, carbon-carbon bond cleavage is a critical step that leads to the formation of a cyclic periodate. This cleavage occurs because periodic acid effectively abstracts hydrogen atoms from adjoining hydroxyl groups, weakening and eventually breaking the carbon-carbon link.

• The ability to break carbon-carbon bonds allows chemists to reconfigure molecules into new forms with desirable properties, an invaluable tool for chemical synthesis.
• This process is particularly beneficial in the creation of various organic and pharmaceutical products by manipulating molecular frameworks.

Understanding how these bonds are cleaved opens up possibilities for innovation in chemical reactions and product formulations.