[wonka_vision]

Hi everyone - I've been performing this monomer synthesis for a couple of years, and I would like to be able to explain a colour change that occurs during the reaction.
The reaction scheme is shown here: http://i.imgur.com/xCnbs.png
It's a standard acid-catalyzed acetal to aldehyde procedure.
The reaction mixture goes from a clear solution to a deep reddish/brown in its final stages. I don't believe polymerization is occurring because I have ample amounts of 4-hydroxy tempo (inhibitor) present. This colour changes regardless of whether or not inhibitor is present.

Any insights would be greatly appreciated!

Thanks

[discodermolide]

Hi everyone - I've been performing this monomer synthesis for a couple of years, and I would like to be able to explain a colour change that occurs during the reaction.
The reaction scheme is shown here: http://i.imgur.com/xCnbs.png
It's a standard acid-catalyzed acetal to aldehyde procedure.
The reaction mixture goes from a clear solution to a deep reddish/brown in its final stages. I don't believe polymerization is occurring because I have ample amounts of 4-hydroxy tempo (inhibitor) present. This colour changes regardless of whether or not inhibitor is present.

Any insights would be greatly appreciated!

Thanks

Can't explain the colour change, why not exchange it off with acetone and ptsa? Reaction temperature is then much lower.

[wonka_vision]

Hi everyone - I've been performing this monomer synthesis for a couple of years, and I would like to be able to explain a colour change that occurs during the reaction.
The reaction scheme is shown here: http://i.imgur.com/xCnbs.png
It's a standard acid-catalyzed acetal to aldehyde procedure.
The reaction mixture goes from a clear solution to a deep reddish/brown in its final stages. I don't believe polymerization is occurring because I have ample amounts of 4-hydroxy tempo (inhibitor) present. This colour changes regardless of whether or not inhibitor is present.

Any insights would be greatly appreciated!

Thanks

Can't explain the colour change, why not exchange it off with acetone and ptsa? Reaction temperature is then much lower.

I'm unfamiliar with this reaction. From what I understand, pTSA is only used in acetal formation (for the protection of aldehydes). Will reaction with aceton and pTSA afford an aldehyde from the acetal group? That would be very helpful! Would you have a reference for this reaction?

Thanks!

[discodermolide]

Hi everyone - I've been performing this monomer synthesis for a couple of years, and I would like to be able to explain a colour change that occurs during the reaction.
The reaction scheme is shown here: http://i.imgur.com/xCnbs.png
It's a standard acid-catalyzed acetal to aldehyde procedure.
The reaction mixture goes from a clear solution to a deep reddish/brown in its final stages. I don't believe polymerization is occurring because I have ample amounts of 4-hydroxy tempo (inhibitor) present. This colour changes regardless of whether or not inhibitor is present.

Any insights would be greatly appreciated!

Thanks

Can't explain the colour change, why not exchange it off with acetone and ptsa? Reaction temperature is then much lower.

I'm unfamiliar with this reaction. From what I understand, pTSA is only used in acetal formation (for the protection of aldehydes). Will reaction with aceton and pTSA afford an aldehyde from the acetal group? That would be very helpful! Would you have a reference for this reaction?

Thanks!

have a look here http://www.organic-chemistry.org/protectivegroups/carbonyl/dimethylacetals.htm

[discodermolide]

I have to apologise. I was thinking about something else. I'm very sorry.

[wonka_vision]

I have to apologise. I was thinking about something else. I'm very sorry.

Not at all - you were actually very helpful! By treating the acetal as a protecting group, you may actually remove it with acetone and TSOH. http://pubs.acs.org/doi/abs/10.1021/ja01649a006
This work is done with ketones, but I'm certain it'll also work with aldehydes.