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Naming compounds

Why is this CH3CH2CHO not CHOCH2CH3. I thought that you count from the nearest functional group.

Propanal_EI_Pypmv3k.jpeg
(edited 2 years ago)
Aldehydes and Ketones are structural isomers. So the image you showed there is Propanal as the OH functional group has 1 Alkyl Group. The formula of CHOCH2CH3 to me implies that it is Propanone.
(edited 2 years ago)
Reply 2
the two formula you list are identical, I guess its just accepted practice that when you write formula the functional group goes last! Its how you would probably draw the molecule!

C2H5OH is ethanol I have never seen it written as OHC2H5!!!!!!

CH3COOH is ethanoic acid, I have never seen it as COOHCH3!
Original post by Markvokin
Why is this CH3CH2CHO not CHOCH2CH3. I thought that you count from the nearest functional group.

Propanal_EI_Pypmv3k.jpeg

with structural formulas you kind of write the formulas as though ur drawing out the formula from LEFT to RIGHT.

so you start with the most left carbon and the non carbons that are bonded to it: CH3
then do the same with the carbon on the right of that: CH2
then the final carbon: CHO

so altogether: CH3CH2CHO
i think your mistake was writing it from right to left rather than left to right
Original post by Markvokin
Why is this CH3CH2CHO not CHOCH2CH3. I thought that you count from the nearest functional group.

Propanal_EI_Pypmv3k.jpeg

You count from the nearest functional group when numbering the carbon atoms. When writing the structural formula, ketone/carboxylic acid groups etc just always go on the RHS, you write the structural formula the way it looks, because you should be able to draw the displayed/skeletal formula from the structural formula
Original post by BarryScott_
Aldehydes and Ketones are structural isomers. So the image you showed there is Propanal as the OH functional group has 1 Alkyl Group. The formula of CHOCH2CH3 to me implies that it is Propanone.

OH is the functional group of an alcohol, CO is the functional group of an aldehyde/ketone. The formula of CHOCH2CH3 still implies propanal (still the wrong formula though) because the CHO still means that oxygen in bonding to the first carbon

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