Chemical Forums
Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: Kaspijs on January 29, 2020, 11:26:35 AM
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According to some sources according to IUPAC a double bond has a higher priority than a single bond. However, some others state that a double bond can be interpreted as two single bonds leading to two of the elements further in chain, unattached to any other. Thus, depending on which principle is used the R/S configuration varies, for example, 2-chloro-3,3-dihydroxypropanal (attached).
So which is the correct one and why is?
Unfortunately I do not reckon the sources, yet Wikipedia proposes the first method and second comes from some sort of Russian org chem book.
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A double bond is counted "backward and forward" by being turned into virtual single bonds.
So an aldehyde group has a C connected to two O's and an H, then an O connected to two C's
The germinal diol or aldehyde hydroate you show has a C connected to two O's and an H, but each O is connected to only one C and one H.
Since the second bond to C is to a higher atomic number atom than to an H, the aldehyde group has higher priority.
If you look up the book by Jakob Fredlos, it is all explained very simply.
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Die Name is wrong, Check Red an black coloured Bonds.
It has two Hydroxymethyl Groups HO-CH2- instead of Hydroxy- group.
2- chloro- 3- hydroxymethyl - 4- hydroxy- butanal