The key difference between alcoholic KOH and aqueous KOH is that alcoholic KOH forms C2H5O— ions while aqueous KOH forms OH– ions upon dissociation.
KOH is potassium hydroxide. It is an inorganic compound we categorize as an ionic compound. Therefore, it can dissociate into two ions as K+ ion and OH– ion. However, if KOH is in an alcoholic solution, then the dissociation gives different ionic forms. Since alcohol contains ethanol molecules (C2H5OH), alcoholic KOH is a potassium ethoxide. Thus, the chemical formula of potassium ethoxide is C2H5OK. On the other hand, aqueous KOH is just KOH in water.
CONTENTS
1. Overview and Key Difference
2. What is Alcoholic KOH
3. What is Aqueous KOH
4. Side by Side Comparison – Alcoholic KOH vs Aqueous KOH in Tabular Form
5. Summary
What is Alcoholic KOH?
Alcoholic KOH is potassium ethoxide. The chemical formula of potassium ethoxide is C2H5OK.
Figure 01: Potassium Hydroxide
When this compound dissociates in water, it gives C2H5O– ions and K+ ions. The C2H5O– ions act as strong bases. Therefore, these ions can abstract beta hydrogen from alkyl halides to produce alkenes. We call this type of reactions as elimination reactions, and it is a dehydrohalogenation.
The reaction is as follows:
C2H5OK + C2H5Cl ⇒ C2H4 + C2H5OH + KCl
What is Aqueous KOH?
Aqueous KOH is potassium hydroxide in water. Here, KOH exists in its dissociated form; dissociation of KOH in water results in K+ ions and OH– ions. Therefore, aqueous KOH has an alkaline nature. Also, the OH– ion is a good nucleophile. Thus, it can undergo substitution reactions. For example, this ion can replace a hydrogen atom from an alkyl halide. The reaction is as follows:
KOH + C2H5Cl ⇒ C2H5OH + KCl
What is the Difference Between Alcoholic KOH and Aqueous KOH?
Alcoholic KOH is potassium ethoxide while aqueous KOH is potassium hydroxide in water. The key difference between alcoholic KOH and aqueous KOH is that alcoholic KOH forms C2H5O— ions and aqueous KOH forms OH– ions upon dissociation. Furthermore, alcoholic KOH compounds prefer to undergo elimination reactions, while aqueous KOH prefers substitution reactions.
Below info-graphic summarizes difference between alcoholic KOH and aqueous KOH, comprehensively.
Summary – Alcoholic KOH vs Aqueous KOH
KOH or potassium hydroxide is an inorganic compound. There are two types of KOH as alcoholic KOH and aqueous KOH, depending on the composition. In summary, the key difference between alcoholic KOH and aqueous KOH is that alcoholic KOH forms C2H5O— ions and aqueous KOH forms OH– ions upon dissociation.
Reference:
1. “Organic Chemistry .” Askiitians Discussion Board, 6 July 2014, Available here.
Image Courtesy:
1. “Hydroxyde de potassium” By Leiem – Own work (CC BY-SA 4.0) via Commons Wikimedia