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Optimum pH range for formation of Schiff bases
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Luzze Arthur
Optimum pH range for formation of Schiff bases
Dehydration requires protonation of the hydroxy intermediate, this clearly is slower at neutral or alkaline pH. Hydroxylamine is basic so at acidic pH it protonates making it non-nucleophilic hence lower pH slows the rate.
Time taken for the reaction to go to completion. If the rate is slowed then other competing reactions (e.g. self-condensation) can and do reduce your yield.
The pH will vary for each substrate and needs to be experimentally determined. This is where a literature search saves you a lot of grief.
Dehydration requires protonation of the hydroxy intermediate, this clearly is slower at neutral or alkaline pH. Hydroxylamine is basic so at acidic pH it protonates making it non-nucleophilic hence lower pH slows the rate.
Time taken for the reaction to go to completion. If the rate is slowed then other competing reactions (e.g. self-condensation) can and do reduce your yield.
The pH will vary for each substrate and needs to be experimentally determined. This is where a literature search saves you a lot of grief.
Can you tell me how to find the relevant literature? I am new to this and cant seem to find any papers or any book on the web that carries the information I need. I specifically require the pH when the substrate is acetaldehyde.More
This depends on the resources available to you. Do you have access to online databases such as Scifinder or Reaxys? If not a Google search on "acetaldehyde oxime synthesis" turns up multiple references to papers, patents and procedures such as this More
Dehydration requires protonation of the hydroxy intermediate, this clearly is slower at neutral or alkaline pH. Hydroxylamine is basic so at acidic pH it protonates making it non-nucleophilic hence lower pH slows the rate.
Time taken for the reaction to go to completion. If the rate is slowed then other competing reactions (e.g. self-condensation) can and do reduce your yield.
The pH will vary for each substrate and needs to be experimentally determined. This is where a literature search saves you a lot of grief.
Dehydration requires protonation of the hydroxy intermediate, this clearly is slower at neutral or alkaline pH. Hydroxylamine is basic so at acidic pH it protonates making it non-nucleophilic hence lower pH slows the rate.
Time taken for the reaction to go to completion. If the rate is slowed then other competing reactions (e.g. self-condensation) can and do reduce your yield.
The pH will vary for each substrate and needs to be experimentally determined. This is where a literature search saves you a lot of grief.
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