Difference Between Alkoxide and Phenoxide

The key difference between alkoxide and phenoxide is that alkoxide forms when the hydrogen atom of the alcohol group is removed, whereas phenoxide forms when we remove the hydrogen atom from the –OH group of the phenol molecule.

Both alkoxide and phenoxide are anions, and they are important as functional groups in chemical synthesis reactions. The alkoxide anion is a conjugate base of any alcohol, but phenoxide anion is the conjugate base of phenol.

CONTENTS

1. Overview and Key Difference
2. What is Alkoxide
3. What is Phenoxide
4. Side by Side Comparison – Alkoxide vs Phenoxide in Tabular Form
5. Summary

What is Alkoxide?

The alkoxide is an anion that forms when we remove the hydrogen atom from the –OH group of an alcohol. Therefore, it is the conjugate base of alcohol. We can write the general structure of alkoxide as RO-. R is an organic substituent. For example, if we have a methyl group there, then the alkoxide is named as methoxide.

Alkoxide can act as a strong base. When the R group is a simple alkyl group (not a bulky group), alkoxides can act as good nucleophiles and as ligands. However, these anions are not very stable in the protic solvents, i.e. water.

Usually, the alkali metal alkoxide occurs as polymeric compounds if the R group is small. Moreover, the alkoxide anion can act as a good bridging ligand as well. There are a few ways that we can prepare alkoxides. For example, we can produce them from reducing metals, electrophilic chlorides, metathesis reactions, and via electrochemical processes, etc. When considering the uses, alkoxides-containing transition metals are useful in coatings and as catalysts.

What is Phenoxide

Phenoxide is an anion that forms when we remove the hydrogen atom from the –OH group of a phenol. Therefore, it is the conjugate base of phenol. If we replace this hydrogen atom from another atom, we can get a new compound. For example, if we replace the hydrogen atom from a sodium atom, we get sodium phenoxide.

The general chemical formula for this anion is C₆H₅O^–. Phenol is acidic, but phenoxide is basic because it tends to accept protons due to the negative charge on the oxygen atom of the phenoxide anion.

What is the Difference Between Alkoxide and Phenoxide?

Both alkoxide and phenoxide are anions and they are important as functional groups in chemical synthesis reactions. The key difference between alkoxide and phenoxide is that alkoxide forms when the hydrogen atom of the alcohol group is removed, whereas phenoxide forms when we remove the hydrogen atom from the –OH group of the phenol molecule. Therefore, alkoxide anion is a conjugate base of any alcohol, but phenoxide anion is the conjugate base of phenol.

Both these anions are basic compounds because they tend to obtain protons from outside to neutralize their negative charge. Moreover, alkoxide anion is useful as a bridging ligand. Meanwhile, phenoxide is useful in organic synthesis reactions to add a benzene ring to another chemical moiety. The general chemical formula for alkoxide anion is RO-, while for phenoxide anion the general chemical formula is C₆H₅O^–.

Below infographic summarizes the difference between alkoxide and phenoxide.

Summary – Alkoxide vs Phenoxide

In summary, both alkoxide and phenoxide are anions, and they are important as functional groups in chemical synthesis reactions. The key difference between alkoxide and phenoxide is that alkoxide forms when the hydrogen atom of the alcohol group is removed, whereas phenoxide forms when we remove the hydrogen atom from the –OH group of the phenol molecule.

Reference:

1. Helmenstine, Anne Marie. “Alkoxide Definition in Chemistry.” ThoughtCo, Nov. 19, 2019, Available here.
2. “Phenoxide Ion.” Chemistry LibreTexts, Libretexts, 5 June 2019, Available here.

Image Courtesy:

1. “Methanolat-Ion” By NEUROtiker – Own work (Public Domain) via Commons Wikimedia
2. “Structural formula of sodium phenoxide” By Chem Sim 2001 – Own work (Public Domain) via Commons Wikimeida