Question

Which among the following reagents converts cyclohexene into trans diol? (a) Baeyer reagent (b) \(\mathrm{OsO}_{4}\) (c) \(\mathrm{I}_{2} / \mathrm{CH}_{3} \mathrm{COOAg}\) (wet) (d) \(\mathrm{I}_{2} / \mathrm{CH}_{3} \mathrm{COOAg}\) (dry)

Short answer

The trans diol is produced by 16;I224;/16;CH3COOAg24; (wet).

Step-by-step solution

Understanding the Reaction

We need to determine which reagent converts cyclohexene, an alkene, into a trans diol. A diol is an organic compound having two hydroxyl (16;OH) groups. The conversion should specifically yield trans diol, meaning the hydroxyl groups are added to opposite sides of the double bond plane.

Reagent Analysis - Baeyer Reagent

Baeyer reagent consists of alkaline KMnO4. It is used to convert alkenes to syn diols, where the added hydroxyl groups are on the same side of the double bond. Therefore, it does not produce trans diols.

Reagent Analysis - 16;OsO424;

Osmium tetroxide (16;OsO424;) also results in the formation of syn diols, which are not trans diols. Thus, 16;OsO424; is not suitable for this transformation.

Reagent Analysis - 16;I224;/16;CH3COOAg24; (Wet)

In a wet environment, 16;I224;/16;CH3COOAg24; forms trans diols. This method involves the formation of iodonium ions that can be opened up by nucleophilic water, resulting in the trans configuration of hydroxyl groups. This reagent is effective for converting cyclohexene into a trans diol.

Comparing Options

Reviewing the options, only 16;I224;/16;CH3COOAg24; (wet) produces a trans diol through its mechanism. The others result in syn products or are not applicable.

Conclusion

Based on the analysis, 16;I224;/16;CH3COOAg24; (wet) is the correct reagent for converting cyclohexene into a trans diol.

Key concepts

Trans Diol Formation

In organic chemistry, trans diol formation is a specific type of chemical transformation. A diol is an organic molecule containing two hydroxyl groups (-OH) attached to different carbon atoms. When these hydroxyl groups are added to opposite sides of a double bond in an alkene, we call it a trans diol formation. This placement gives the molecule a distinct, staggered 3D shape.
In the case of cyclohexene, an alkene, the transformation into a trans diol requires precise control over how and where these hydroxyl groups are introduced. This positioning is crucial, as it affects the resulting compound's physical properties and reactivity.
It's important to utilize reagents that ensure the hydroxyl groups are added in a trans configuration, meaning they are on opposite sides of the double-bonded plane. This trans configuration can then be leveraged in synthesis reactions to create building blocks for more complex chemical structures.

Organic Chemistry Reagents

Organic chemistry reagents are substances or mixtures used to cause a chemical reaction or to analyze other chemical substances. They play a crucial role in transforming substrates like cyclohexene into different products. The choice of reagent can significantly affect the course and outcome of a chemical reaction.
Several reagents are commonly used in organic chemistry for diol formation:

• Baeyer Reagent: Composed of alkaline potassium permanganate (KMnO extsubscript{4}), it is suitable for the formation of syn diols where both hydroxyl groups appear on the same side.
• Osmium Tetroxide ( ext{OsO}_{4}): Another widely used reagent for syn diol formation, causing hydroxyl groups to add on the same face of the double bond.
• Iodine-based Reagents: Designed to target trans diol creation, especially when used in combination with moisture or specific solvents that allow for the opening of cyclic intermediates like iodonium ions.

Each reagent works through specific mechanisms, which dictate the final orientation of the added functional groups. These mechanisms include the formation of intermediate compounds, which guide the reaction towards the desired trans or syn product based on the conditions involved.

Iodine Reagent

The iodine reagent, when combined with silver acetate ( ext{CH}_{3} ext{COOAg}) and applied in a wet environment, becomes particularly effective for converting alkenes into trans diols. This reagent works through a fascinating chemical mechanism, involving the initial formation of iodonium ions.
When iodine ( ext{I}_{2}) reacts with cyclohexene, it forms a cyclic iodonium ion intermediate. This occurs when iodine adds across the double bond of cyclohexene, forming a three-membered ring structure.
In a wet condition, water acts as a nucleophile, attacking the ring from the opposite side of the iodine atom. This opens the iodonium ion and results in the hydroxyl groups being placed on opposite sides of the original double bond plane, thus yielding a trans diol.
This process is specific to wet conditions, providing greater control over the stereochemistry of the product. In this context, moisture is more than a mere solvent, serving an active role in the molecular transformation, ensuring the formation of trans diols from cyclohexene.