Sciencemadness Discussion Board

theoretical carbonyl protection

Vanry - 20-7-2018 at 00:54

hi everyone !

I was wondering what was the difference between using methanol, ethylene glycol or other R-OH coumpound to protect a carbonyl.

What differenciate them theoretically ? why some of them are prefered ? what is the theory behind that ?
I've seen a lot of methal/EG uses in publications but I have no book discussing why.
thank in advance for your knowledge ;)

[Edited on 20-7-2018 by Vanry]

brubei - 20-7-2018 at 12:24

The use of different alcohols ofer a wide range of protection, some cetals are less sensitive than others to acidic condition or heating.

Also don't forget that protecting a function is a loss of energy, you have to spend time and chemicals to do your protection and deprotection reactions. Strong protection may require strong deprotection and must be used only if your reaction condition need it. if your conditions are less sensitive, a weaker protection can be used and will be removed faster, cheaper and without action on other function.

However, another application is sugar chemistry. Sugars are rich in OH groups and chemists often wants to protect some and keep others free to continue their synthesis. All these OH group are reacting different way depending to the choice of carbonyl, playing with the conditions of protection and the deprotection sensitivity allow to control selectively wich OH group will be free or protected.

The famous book "Protective groups in organic synthesis" will give you a lot of exemples. Sugar organic chemistry books too.

[Edited on 20-7-2018 by brubei]

Vanry - 21-7-2018 at 18:09

Quote: Originally posted by brubei  
The use of different alcohols ofer a wide range of protection, some cetals are less sensitive than others to acidic condition or heating.

Also don't forget that protecting a function is a loss of energy, you have to spend time and chemicals to do your protection and deprotection reactions. Strong protection may require strong deprotection and must be used only if your reaction condition need it. if your conditions are less sensitive, a weaker protection can be used and will be removed faster, cheaper and without action on other function.

However, another application is sugar chemistry. Sugars are rich in OH groups and chemists often wants to protect some and keep others free to continue their synthesis. All these OH group are reacting different way depending to the choice of carbonyl, playing with the conditions of protection and the deprotection sensitivity allow to control selectively wich OH group will be free or protected.

The famous book "Protective groups in organic synthesis" will give you a lot of exemples. Sugar organic chemistry books too.

[Edited on 20-7-2018 by brubei]


Thanks a lot. It’s just for a grignard réaction, I don’t think grignard need heavy protection. Nonetheless, who is the author ? Et avec ça qui l’édite en français ? Si il est édité en français bien sûr ;)